DNA – The Only Way?

I’ve been struggling to write a post about the new TV show ‘Pluribus’ but it’s actually huge and therefore hard to talk about in a single piece, so for now, and possibly instead of that, I’ll just be talking about a scientific point it raises and it isn’t really about the series. There’ll be spoilers for about the first ten minutes of the first episode and then I’ll be moving off the subject. Here goes.

At the start of the first episode of ‘Pluribus’, astronomers detect a signal from the TRAPPIST-1 system around 600 light years away in the constellation of Cygnus. It repeats every seventy-eight seconds and consists of a series of four types of signal which they quickly realise represent the four bases of RNA, cytosine, guanine, adenine and uracil. This makes sense, in a way, as RNA is used to send messages from DNA for transcription into proteins, and it’s doing the same job here. This made me wonder a couple of things. How did they know it was uracil and not thymine, and RNA but not DNA? Also, does this mean that RNA and DNA are universal codes for genetic information, everywhere there’s life, or is it individually customised for different recipients, in which case how did they know terrestrial life used that code? Seems like insider information is involved somewhere.

So, crystallising that thought, this is the situation. All known life here on Earth uses one of two complex types of molecules, deoxyribonucleic acid and ribonucleic acid, DNA and RNA. At this point I’m stuck because I have no idea how much is common knowledge. If I get this wrong, I’m going to lose a lot of people. So I’m going to assume that everyone knows the remarkable general double helix with rungs structure of DNA, how its coils are themselves in coils so that it’s packed together very closely most of the time, that most of it doesn’t carry genetic information but has other functions related to it, that it has sides made of alternating sugar molecules and phosphate groups and four types of bases which link up in specific pairs, adenine with thymine and cytosine with guanine. RNA is generated from DNA and has a different, simpler structure, again with a sugar molecule alternating with phosphate groups and again four bases, except that instead of thymine it has a base called uracil. RNA is used to transfer information to ribosomes, which are like playback heads except that instead of sound they produce proteins, one amino acid at a time. Although most species of animal, plant and other organisms use DNA to store their genes, many viruses use RNA instead. RNA is less stable than DNA, so for example whereas animal or plant remains from many millennia in the past can have their DNA information extracted in a form increasingly corrupted with their age, RNA is not the same and doesn’t last long.

This is important. Please tell me if I’m assuming too much and if I’m not writing clearly. I really struggle with brevity, clarity and trying to work out what people do and don’t know about things, and one way of addressing this might be to get some feedback. In a sense, this entire blog post is a test of my ability to communicate clearly and well at least as much as it is about DNA.

So, I have questions, some of which I know some of the answers to but most I don’t. DNA can be considered to have the following components: deoxyribose, phosphate, adenine, thymine, guanine and cytosine. RNA has ribose instead of deoxyribose and uracil instead of thymine. The question is, are any or all of these essential for any molecule carrying genetic information within an organic life form, or are there other possibilities? How rigidly restrained is this aspect of biochemistry? This could be framed as a question about alien life but in fact it’s as relevant to biochemistry as it’s actually known to be on this planet as it is to that possibility.

First of all, the bases. There are two types of these: purines and pyrimidines. Purines have two rings in their molecule and pyrimidines only one. I remember this by thinking that the long name describes the short molecules and vice versa. Purines include some other familiar compounds including caffeine and the related stimulants often found with it. A particularly prominent purine is guanine, which forms the reflective layer at the back of many vertebrate retinae such as dogs and owls and increases their visual sensitivity in low-light conditions, and also the white cross on the back of garden spiders. They tend to be broken down into uric acid, so a diet high in DNA can contribute to gout and kidney stones and also conditions involving a high turnover of DNA such as leukaemia can also have these effects. Pyrimidines strike me as more obscure. Vitamin B1, thiamine, is a pyrimidine, as the name of thymine suggests, but as I understand it, although they’re widespread most of them are not well-known. However, similar pyrimidines to the ones found in nucleic acids are used as anti-cancer and anti-viral drugs.

Hence we have a system with four bases of particular kinds which can pair up with each other and consecutive groups of three bases are known as codons, each encoding for a particular amino acid, which are the blocks of proteins, as well as acting as “punctuation” such as full stops marking the end of a protein synthesis sequence. That’s sixty-four possibilities. However, since other bases can exist, it’s hypothetically feasible that these data can be stored more densely and efficiently. In particular it seems odd that uracil occurs in RNA but not DNA, but the reason for this is that it’s less stable and therefore can’t reliably encode for a long period of time, so it’s not so much that it’s used in RNA as that it isn’t used in DNA, and maybe at some stage it was but wasn’t selected for. This, then, is the first identifiable factor in the structure of DNA which determines its nature. I think there are probably at least four more usable bases, and this would double their data density. What it might not do, however, is enable evolution, as it might be that these bases are less amenable to mutation. For all I know, the first life forms in our lineage may have had different bases but couldn’t evolve as fast and therefore wasn’t able to compete with other organisms and aren’t our ancestors, even though there was nothing wrong with the basis of their genomes.

The next issue is sugar. Two sugars are involved and give their initials to the first letter of DNA and RNA. They’re pentoses, like fructose, rather than hexoses like dextrose or disaccharides like sucrose. Again, the explanation for the difference is durability and stability. The hydroxyl group on the second carbon which is absent on the deoxyribose molecule means it’s more stable than ribose and less likely to be altered by water. The presence of this hydroxyl group on the ribose molecule makes it easier to break down, ensuring that protein synthesis stops when it needs to. However, three- and four-carbon sugars could form the basis of the backbone instead of ribose or deoxyribose. Any more than five carbons stops double helix working: it gets in the way of the shape, making packing into the coils and supercoils unfeasible, and also makes it more reactive and also encourages branching. The double helix arrangement isn’t just pretty. It makes it possible to pack it into a small space, such as in chromosomes. It is possible for hexose nucleic acids to form but they don’t become double helices. Fructose is of course another pentose but the position on its molecule at which nitrogens from the bases can form are in the wrong place and the arrangement would be too crowded. Inulin, which is the daisy family’s alternative to starch which tastes like Jerusalem artichokes because those are in that family too, and sucrose itself both contain fructose but it’s not used in nucleic acids for this reason. It’s also thought that the processes which led to living processes preferred pentoses over other types of sugar, so life built on what was available.

That leaves the phosphate groups. These keep the molecule regular in shape and enable the DNA to bind to histones, which are the proteins making up much of the chromosomes around which it winds. Obviously this doesn’t apply to RNA because it isn’t wound round anything. Actually, it doesn’t apply to prokaryotic organisms such as bacteria either because they don’t have histones, but they do have nucleoid-associated proteins which do similar jobs. Bacterial DNA is in loops called plasmids. Plastids (not plasmids) have less DNA than free-living prokaryotes because many of their genes have been transferred to the nucleus.

Surprisingly, phosphate groups are not essential to the structure of nucleic acids and are in fact weaker than other options. For instance, glycine, the simplest, and the only non-chiral amino acid, can bond the sugar molecules together. Amide bonds are an option. There are also some different arrangements with phosphorus itself. These stronger bonds, though, can’t cross membranes as easily. Now I’ve previously mentioned how phosphorus may be the dog in the manger which explains the Fermi Paradox, but this is clearly not to do with DNA or RNA as it’s entirely feasible for an adequate alternative to DNA to exist without phosphorus, but with glycolysis and the Krebs Cycle where so far as I can tell it really cannot be replaced. This does however open up the possibility of life existing in the Universe in places with rather less phosphorus than this solar system. Incidentally, a decade or so ago organisms were found in a lake which were thought to be able to substitute arsenic for phosphorus in their DNA, but it turned out they were just really good at finding phosphorus.

It does seem, then, that fairly dramatically different but still perfectly functional analogues to DNA and RNA could exist, and even that they might be more likely than those two to form in an environment with less phosphorus. Getting back to ‘Pluribus’, it’s exceedingly unlikely that it’s the kind of series for this to matter. It’s known that there’s a gene for the receptor which detects the odour of Convallaria majalis in the genome received, which is lily of the valley, and this is probably a throwaway reference to that storyline in ‘Breaking Bad’, and this receptor is also found in sperm cells and attracts them towards the ovum, although it’s thought nowadays that the ovum chooses the sperm rather than the other way around. But it leads to two organisms joining. I very much doubt whether any of this matters to the show. However, it is possible to push this further for the sheer scienciness of it all. Yeah, science!

OK, so here are two alternate scenarios regarding the origin of life on Earth. One is that life as we know it originated somewhere in the Universe before the birth of the solar system and spread through the Galaxy, including this solar system. The other is that life arose many times, in this solar system and elsewhere. In the first scenario, for which there’s actually quite a bit of evidence, it’s feasible for many worlds to have life with identical biochemistry, since all of it would have the same ancestry. In such a situation, the transmission of the RNA from TRAPPIST-1 makes sense and isn’t customised for life here, at least as far as genetic code is concerned. However, the fact that it uses the code for this receptor would seem to mean a remarkable degree of convergent evolution, the presence of the gene in the last universal common ancestor with the life in that system or detailed knowledge about life here. Another is that there are various different ways of storing and transferring genetic information, in which case it’s a mild coincidence that the signal happens to be RNA base-pairs. Given what I’ve suggested here, there seems to be no particular reason why the chemical basis of the genome should be the same. There are more complex possibilities, such as there being various different independent empires of life throughout the Galaxy, and this one happens to be the same as ours.

All of this is most unlikely to have much to do with the plot of the series. I don’t know how ‘The Walking Dead’ ended but there was initially speculation about the origin and a possible cure for the Wildfire virus, but later on it seemed to become clear that these questions were irrelevant to the story. If this later changed, to my mind this would detract from the quality of the series. Whether the same is true of the ‘Pluribus’ virus remains to be seen but it doesn’t feel like treating it as a central mystery would add to the quality of the series, which is currently very high indeed of course because it’s Vince Gilligan. What’s occupying everyone’s minds right now, just after episode 5, ‘Got Milk’, is of course whether “Soylent Green is people”.

Beyond The Looking Glass

1. The Risks of Mirror Life

This one will have to start pretty far back from where it ends to make much sense. I have already stuck an idea along these lines on the Halfbakery, which I’ve begun to frequent anew in the past few weeks. It’s not exactly a simpler place and time, more of a more complicated one, but that’s why I like it.

First of all, this post is going to be quite wide-ranging and extensive in terms of technical details. The reason for this is that it’s been suggested to me that I submit the idea as a non-peer reviewed scientific paper rather than write a blog post about it, but I don’t have a lot of respect for journals that allow that, particularly considering that I’m not in an academic community relevant to the field and have only fairly basic education regarding biochemistry and other branches of chemistry. In order to produce good-quality coherent ideas in a particular academic discipline, it’s usually necessary to have people to bounce them off and get torn down numerous times. I don’t have this even in philosophy, and although I have carried out quantitative research in herbalism, mainly due to the parlous state of CPD in that area at the time, I haven’t got my own lab. So I’m posting this here instead, where I hope it will vanish without trace.

I’ll start with “life as we know it”. Life as we know it is a complex system of organic carbon compounds interacting and reacting in aqueous solutions partitioned off from one another by membranes made of molecule-thick layers of oil in which various proteins float, some of which control movement of substances across these barriers. On some level, this is actually all life is, or at least the life we’re familiar with. The code for doing all this is stored in DNA, gets read and turned into proteins which further down the line may in turn work on other substrates to make something else such as cellulose or dental enamel, and the whole system is powered by a process whereby usually sugar is broken down to release energy through adenosine triphosphate called glycolysis, which then can go in several possible directions depending on the organism: fermentation, where ethanol or acetic acid is produced, other anaerobic respiration, where lactic acid is produced, or (drum roll please!) the Krebs Cycle, where the stuff is converted into various organic acids and combined with oxygen, then fed back into the start of the cycle, which is by far the most energetic pathway. That’s another thing that life is, in a slightly more detailed version.

It’s occurred to me, incidentally, that in theory some kind of motor could be built which digested cellulose, starch and sugars and converted them into movement, so that there could be a literal “Krebs Cycle”, i.e. a motorbike which runs on food, and that’s on the Halfbakery too. A cyclist is doing this in a roundabout way of course, and there are microorganisms who can convert energy released by reputation into rotary motion using microscopic motors which work by alternating electrostatic attraction and repulsion, so this is doable, though also possibly a bit pointless and unethical.

Thinking of living things as complicated wet machines might help to get me to the next stage of understanding what I’m about to say. Suppose you have a machine with clockwise screw threads and screws, say a clock, and the mechanism tells the time by moving hands around a dial in a clockwise direction. That’s fine and we know about those, but there could be an alternative mechanism which is 100% identical but has counter-clockwise screw threads and screws and works exactly the same way, but is a mirror image of the other clock, and it still works fine, tells the time accurately and so on, but every part is the opposite way round, so its dial works counter-clockwise. If a screw were to work loose or the winding gear needs replacing, you wouldn’t be able to get spare parts from the other clock most of the time to repair the clockwise one. It just wouldn’t work, and if it was working in the first place and you replaced a working part from one clock with the corresponding part from the other, it would often break it. Similarly, if you drive from a right-hand drive country into a left-hand drive one but carry on obeying the traffic laws of the other country, you’d be putting yourself and others in danger and either have an accident or get arrested. Life’s like that.

Life really is like that. Many of the molecules making up living things are not symmetrical. They’re either left or right-handed. In fact, although there are specific molecules in biochemistry which can be of either chirality, the word for this handedness after the Greek word for “hand”, the central parts of life chemistry consists of proteins and amino acids which are left-handed and sugars and carbohydrates are right-handed. It’s fair to ask how a molecule can be said to be left or right handed when this seems to be an arbitrary decision but in fact homochiral solutions of molecules, that is, molecules which are all right-handed or all left-handed, bend light shone through them to the left or to the right depending on their handedness, so it isn’t arbitrary and this explains how it can be said that sugars are generally right-handed and amino acids left-handed. It’s also possible for molecules to have more than one chiral centre, meaning that there could be four different versions of a particular molecule with two such centres and so forth.

Although the central machinery of life is chiral, the end products of that machinery can be either way round. For instance, the scent of orange and the scent of lemon are both contributed to by a molecule called limonene, but the two molecules have opposite chirality. For some reason, the lemony version is much more common than the orangey one. Another pair of examples is the odours of spearmint and caraway. The name “dextrose” is almost a synonym for “glucose”, but the “dextro-” refers to the right-handed version alone. There is also a “levulose”, which was going to be introduced as a non-calorific sweetener but it didn’t happen. I don’t know why, but the reason it was suggested is that glycolysis and the Krebs Cycle wouldn’t have been able to break it down or release energy from it. Another example, from pharmaceuticals, is levothyroxine and dextrothyroxine. Both are amino acids but whereas levothyroxine is a thyroid hormone used for hypothyroidism, dextrothyroxine is its right-handed version and was used to lower cholesterol, but isn’t on the market because of cardiac side-effects.

Usually when drugs are manufactured, because the process is through industrial chemistry rather than from living things, they are what’s known as a “racemic mixture”, i.e. a roughly equal mixture of left- and right-handed molecules. On the whole, drugs on the market stay as these mixtures unless it turns out one chirality has serious side-effects as with dextrothyroxine, in which case some complex processing has to be used to purify them into the active and safe form alone. This means that often when someone takes medication from orthodox pharmaceuticals, they are actually taking twice the dose they need and half of the medication has no action and is simply excreted.

Some simple biochemicals are symmetrical, for instance the simplest amino acid, glycine, which incidentally is the only such acid found in interstellar space. Left- or right-handed molecules also very slowly shift to a racemic mixture over a known period of time depending on their temperature, and this enables ancient biological remains to be dated if they’re too old for radiocarbon dating but not old enough for other methods. Most Neanderthal remains fall into this category, and for this reason Young Earth creationists are particularly keen on casting doubt on its accuracy. Of course not every molecule involved in living things is affected by this. Water, carbon dioxide, nitric oxide, carbon monoxide, calcium phosphate, calcium carbonate and so forth are not chiral at all. Also, there’s no firm theory about why this has happened, or for that matter why macromolecules such as proteins and polysaccharides aren’t built out of whatever chiralities of subunits which would optimise their structure and function, but for some reason they aren’t. It might simply be that some process before life even emerged eliminated most of the molecules of the “wrong” chirality. This oddity is, incidentally, paralleled by another weird thing about the world, which is that it’s made of matter rather than antimatter. For some reason, antimatter seems to have won out in the Universe and the occasional bit of antimatter, for instance above thunderstorms or emitted by bananas, is not in common supply. It’s unsurprising that it gets eliminated quickly because it’s surrounded by matter, but why should there be more of one than the other in the first place? As I understand it, in fact matter and antimatter are themselves of reverse chirality but in a higher set of dimensions than the four we usually consider, but I may have got that wrong.

Mirror molecules can be useful. For instance, if a protein drug can be made entirely out of right-handed amino acids, it’s likely to last longer in the body because it can’t be easily broken down by the left-handed enzymes we produce. In situations where a mirror-image molecule is highly toxic but its counterpart is a valuable drug, finding a way to synthesise one set rather than both and throwing half away after a complicated and energetically and economically expensive sifting process is obviously more desirable provided that that process itself doesn’t need much energy.

If you imagine Alice stepping through the looking glass into a world where she is still the same way round but the rest of the world is the other, she would be in quite a predicament if she couldn’t get back. She’d be able to breathe the air and drink the water without any trouble, but she wouldn’t be able to derive any nutrition from the food except the minerals and she’d simply starve to death. After that, her body might also fail to decompose properly because in this scenario she actually isn’t worm food. This, I think, might be similar to the situation astronauts might find themselves in if they were to land on a habitable, life-bearing planet in a distant solar system: there’s only a 50% chance they’d be able to eat anything at all usefully and a lot of it would probably be as poisonous as cancer chemotherapy drugs as well. On the other hand, if there is life elsewhere, maybe it all has the same bias as ours because the process leading to that came before life first appeared.

It’s also been suggested that mirror life, as it’s been called, does actually exist on this planet but we can’t easily detect it. Desert varnish is one suggestion of what’s been called a “shadow biosphere”, which uses molecules with the opposite chirality. It’s an orange to black patina which forms on rocks in arid conditions and seems also to exist on Mars, so if it does turn out to be connected to organisms that would presumably mean there’s been life there. The idea that it’s shadow life is however no longer popular, but if it does exist it would effectively be alien life on Earth, which has always been here but has nothing to do with the life we know about.

Mirror life constructed from scratch is not possible using existing technology, but scientists estimate that it’s ten to twenty years away right now, assuming human beings continue to work in that direction. However, we now have some kind of apparently competent AI which could accelerate that process, and this has led scientists to worry sufficiently to publish rather alarming papers attempting to warn the world of the risk. In order to clarify this, I should point out that the microbes we know about can be divided along the lines of their nutrition into those needing complicated organic molecules to survive and those which can thrive on simpler minerals alone. Those which can do that, known as “lithophiles”, a word which can also be used to refer to chemical elements which tend to be found in rocks near Earth’s surface, extract energy and take nutrition from simple substances such as carbon dioxide and may photosynthesise. This is an important category from the perspective of mirror life.

Like the clock, there is absolutely no reason so far as anyone knows why an organism couldn’t be built all of whose chiral molecules are mirror images of those found in known living things on Earth. However, in many cases this organism could well encounter a major problem early on if it happened to be an animal. There would basically be no food for it. There’d be minerals for sure, and oxygen, carbon dioxide and other things essential for life, but no calories from sugar or fat and no amino acids from protein. They’d simply waste away. This might sound reassuring, as it means that if scientists or AI did manage to build such an organism it would be self-limiting as it would need special nutrients. However, what if it were a lithophile? It wouldn’t then need molecules of a particular chirality because it could make them itself. Actual lithophiles (also called lithotrophs, which is less ambiguous, but I’ll stick with how I started) don’t produce reverse-chirality compounds, so at first it might seem that there’s no risk of this happening, but the reason for this is that there’s a genetic link between them and us, and all related life does prefer the chiralities I mentioned above. If an organism is lithophilic and has reverse chirality to known life, it could end up using up biomasse and be a dead end, where those substances could never return to the food chain because there’s nothing available to process them. So the risk in the general case is that large amounts of living matter would gradually turn into mirror life and never come back.

There’s another risk too. I’ve mentioned that one of the benefits of mirror molecules is that they last longer because organisms lack the enzymes to break them down. This could be a hazard as well as a benefit. It’s been suggested that this means that a microorganism entering the human body, for example, could end up using up all the resources it can use within someone’s body while slipping under the RADAR of the immune system, which would simply never detect it. It could then multiply unhindered, taking over the entire body without anything being done about it, pretty quickly killing the patient. It’s been calculated that if a single bacterium were to multiply at its usual rate, it would overwhelm the world within days. This doesn’t happen because bacteria are part of an ecosystem which consumes and processes them in various ways, but mirror life wouldn’t be.

I’m not sure this is how things would work out, but the risk exists, and does so in two different ways. One is simply the reckless production of mirror life for something like drug manufacture, which does have a positive side but relies on containment to avoid this danger, and given that sterile technique can easily fail, as occasionally happens with, for example, post-operative infections, it’s bound to happen eventually. The other is that it could happen as a result of out-of-control, misaligned artificial intelligence might use mirror life to wipe out all life on Earth on the grounds that it gets in the way of their development and dominance, and it’s been suggested that this could happen within three years from now (2025).

My response to this is something which I can’t come to terms with, which is happening to me more and more often nowadays. The problem is that it’s an example of something which sounds alarmist, leading to doubt that it’s realistic, but I’m also aware of normalcy bias where people, including me, tend to think things will carry on as they have for a long time for us, and as I’ve talked about before on here this is a risky way of thinking. In the case of the risk of mirror life to human health, and more widely to other organisms which immune responses which involve recognising foreign material and defending the body against it, my problem is that I felt I didn’t have much choice but to retire my studies into immunology because they seemed to be leading me in the direction of being anti-vaxx and I was aware that hardly anyone with education and experience in the field had that position. I should point out that this was not the usual “do your own research” thing where people end up watching YouTube videos produced by flat Earthers or whatever. It was a project I pursued where I bought and read the standard immunology and microbiology text books, and they still led me away from a pro-vaccination position. I should stress, incidentally, that I’m not against vaccination, but equally, that this pro-vaxx position is not evidence-based for me but relies on trusting experts. Anyway, the consequence of that is that I cannot safely explore the opinion I now have on this matter as regards mirror life, which is that it really, really seems to me that since the body can recognise and act against haptens, as it does for example with nickel allergy, nickel being a simple, non-chiral metal, surely it could do the same against mirror antigens? So I’m intellectually paralysed here. I can’t proceed.

2. An Alternative

But there is another way forward for me, beyond the looking glass of mirror life. The idea of life originating beyond Earth being based on different principles has been discussed in xenobiology and science fiction for many decades now. The idea of reverse chirality is the most conservative of these ideas. It would be very surprising if it turned out that mirror life couldn’t exist, and equally surprising if it emerged that all life throughout the Universe was as similar to life here to that extent. In this situation the burden of proof is on someone claiming such life is impossible rather than the other way round, and that’s unusual, possibly unique in all the suggestions which have been made in not involving a radical departure from known biology. Some of the others include: ammonia or hydrogen sulphide as a solvent instead of water, arsenic compounds instead of ATP for respiration, chlorine breathing instead of oxygen, and of course the most famous of all: silicon-based life.

Now, I’ve discussed silicon-based life before although I can’t remember if I’ve done it on this blog. One of my most popular videos on YouTube is about it, and two very different ways in which it might happen. Those who consider silicon-based life generally fall into two camps. They either believe it’s impossible or they believe it’s possible in circumstances very different to Earth’s. As sometimes happens with me, I think the situation is somewhat different. I think that if there is life elsewhere in the Universe, silicon-based life has never arisen on its own because the set of conditions it would need are not going to happen by chance. However, I also believe that silicon-based life could be technologically created in a carefully controlled environment. It’s not that it can’t exist: it’s that it would never happen without help.

First of all, I should point out that I’ve had two goes at this in different ways. I’ll outline the general principles first. The general idea with silicon-based life is that silicon seems to be the chemical element most similar to carbon. It can form up to four bonds with other atoms, forms into chains and rings and in those conditions can still bond with other compounds and atoms. Incidentally, the same seems to be true of boron and in fact boron even has some advantages over silicon, but it isn’t abundant enough to be a real contender in the world without some kind of intervention, so silicon is a stronger focus for most people. It’s a very common element indeed, being the second most abundant element in Earth’s crust after oxygen, far more widespread than carbon in fact, even though life here is based on that rather than silicon. It also has the capacity to form a wide variety of compounds, like those of carbon, including oils, waxes, rubbers and inflammable substances like mineral oil and even compounds similar to alcohols. Some silicon compounds can even replace certain hormones and have similar actions to them in the human body. There’s a second set of compounds as found in rocks and minerals as well as elsewhere, some of which, the amphiboles, form double helices of units somewhat like DNA’s structure although much simpler and apparently not carrying genetic information as such.

So it all looks quite promising, doesn’t it? Well it isn’t, not at all. A hint to the implausibility is found in the fact that we live on a planet substantially composed of silicon compounds and yet life here is based on the much scarcer (for this planet, not everywhere) carbon. At least in the conditions found here, something seems to have prevented it from getting anywhere.

Unfortunately, there are huge barriers to the possibility of silicon-based life. Firstly, the current terrestrial conditions make it impossible, although it should be remembered that organic life is also impossible on most other planets in this solar system and even through most of the volume of our own. Oxygen combines readily and almost irreversibly with silicon, to the extent that the main silicones are based on combined silicon and oxygen chains rather than those of silicon. Water and silicon react exothermically, i.e. generating heat, oxidising and releasing free hydrogen, initially producing silicon monoxide which rapidly becomes silica. At that point the silicon is basically stuck in that molecule and nothing is going to coax it out apart from rather extreme measures outside the realm of biology. Moreover, many silicon compounds other than silicates are destroyed by ultraviolet light in sunlight. This means that any silicon-based life in this sense (there are others) would have to be in an environment devoid of liquid water, free oxygen and probably also daylight.

However, this doesn’t make it impossible. Water is a very special compound which is difficult to replace as a solvent for living organisms, one of its important properties being polarity. Its molecules are negatively charged on one side and positively charged on the other, enabling them to do various things important to life. For instance, it makes it a better solvent, so biochemical reactions can occur more easily or at all. It also enables membranes to exist between different parts of cells and also between them and the outside world or the rest of the body. It helps proteins fold and keeps DNA stable. It also has a number of other benefits such as ensuring that the bottom of a body of water stays liquid, meaning that they don’t freeze from the bottom up because ice is lighter than water, and enabling plants to pull water into and up themselves more easily. If there’s to be biochemistry “as we know it”, even silicon-based, it definitely seems like there has to be a polar solvent and that can’t be water for silicon. The usual alternative suggested is ammonia, which has similar properties but much lower freezing and boiling points at atmospheric pressure on Earth. Clearly if alien life is being considered, Earth is not the environment. Ammonia boils at -33 degrees C.

All this, then, doesn’t sound very promising. Maybe there’s a planet or moon somewhere orbiting another Sun-like star about where our asteroid belt is which has ammonia oceans at whose bottom silicon chemistry can operate in a more complex way than on Earth, but the options are limited, not least because as well as all these drawbacks, silicon compounds tend to be less stable even in ideal conditions than organic carbon compounds and the variety of such compounds is smaller for various reasons. One is that silicon, unlike carbon, struggles to form double or triple bonds due to being a larger atom, and for some reason I don’t understand, chains of silicon molecules can’t be as long as carbon ones. Right, now I’ve said I don’t understand, and this is the problem. Although I am good at theoretical chemistry to some extent, I haven’t studied inorganic chemistry above GCSE level formally and my knowledge of biochemistry, although it’s considerably better, is also not really at first degree level in most respects. I know what I need to know to understand pharmacology, medical lab science, physiology, phytochemistry and so forth, but not much beyond that. Therefore, my knowledge tends to run out at this point. Even so, I’ll continue, taking a bit of a detour. Bear with me.

There are languages with very large numbers of sounds. ǃXóõ, for example, has fifty-eight consonants and thirty-one vowels. By contrast, Rotokas, depending on the dialect, has as few as six consonants and five vowels. Nevertheless both do their job of facilitating communication equally well. There will of course be situations where one will have a word the other lacks, such as, I dunno, the shrub Welwitschia having a name in  ǃXóõ but not in Rotokas, or the ti plant having a name in Rotokas but not ǃXóõ, but it would still be possible to refer to them somehow, with a loan word, an international term or by describing them. Likewise, there are different number bases and notations, such as binary, decimal, duodecimal or Roman or Western Arabic numerals, but maths can be carried out in all of them. This is slightly different because Roman numerals are not good with the likes of negative numbers, decimal fractions or large integers, for example. Another example is expressive adequacy. It’s possible to express any logical operation using a single operator, depending on which one is chosen – there are in fact two, one of which is NAND – “is incompatible with” or “not both. . . and. . . “, but we usually rely on about half a dozen. Then there’s Turing completeness, which is the ability of a machine to act as a general purpose computer. The Z80 CPU as used in the ZX Spectrum had 694 separate instructions, but it’s possible to build a computer with just one instruction – subtract one, then branch if negative – which would still function as a computer, although probably a very slow one.

In other words, there are two opposite poles for solving a variety of problems. One pole involves a large number of different items to address it, the other very few or even only one. This applies in all sorts of different situations: language, arithmetic, formal logic, computer science and probably a lot of other areas. One of these, in my uninformed opinion, might be biochemistry. As it stands, DNA is made of two backbones of deoxyribose phosphate and four different bases somewhat similar chemically to uric acid and caffeine and RNA is similar except for being ribose phosphate, not being a double helix and having one different base. There are generally understood to be twenty-one amino acids which compose proteins, although there are also others such as those with selenium or tellurium in them instead of the sulphur found in a couple of the usual ones, the neurotransmitter GABA, thyroxine and so on. Then there are the carbohydrates and lipids, which again are built up from simpler units such as dextrose, glycerol and docosaehexanoic acid. The actual macromolecules are very varied, but they tend to be composed of smaller and less diverse components. My possibly naive claim is that silicon-based macromolecules could be built out of larger numbers of less varied units, which would incidentally already be somewhat larger than their carbon-based analogues due to silicon atoms being bigger. Nonetheless, all this is happening on such a tiny scale that even molecules an order of magnitude larger are still minute, and it’s basically a technical difference most of the time.

That, then, seems to be completely fine and maybe this makes the idea of silicon-based life more realistic, but there’s yet another obstacle. The interstellar medium is the collection of extremely sparsely distributed matter between the stars. It amounts in general to something like just creeping into double figures of molecules or atoms per litre of space, and most of that’s hydrogen and most of the rest of it helium, so actual compounds like water or methane are pretty rare, but they can be detected using spectography and in some places they’re more concentrated than others, such as in nebulae including the one near the centre of the Galaxy which consists largely of raspberry rum – I’m not kidding: it’s called Sagittarius B2 and is 150 light years across. In all of this, you can find all sorts of stuff, including table salt, “lo salt”, nitric oxide, hydrochloric and hydrofluoric “acids” (they don’t act as acids because they’re isolated compounds), carborundum, actually yeah, let’s make a massive long though incomplete list: aluminium hydroxide, water, potassium cyanide, formaldehyde, methane, formic and acetic “acids”, methanol, ethanol, glycine (an amino acid), ethyl formate (raspberry flavour), acetone (pear drop scent and nail varnish remover), buckyballs and calcium oxide (quicklime). This is by no means an exhaustive list. Most of the molecules I’ve mentioned, but not all, are organic and contain carbon (I should explain that as it sounds tautological), and in fact there are also silicon compounds including silane, which is the silicon-based version of methane. However, there are far fewer compounds with silicon in them than carbon ones, and in fact some of them contain both silicon and carbon.

Back in the day, the Miller-Urey experiment used a mixture of simple compounds incubated with an electrical discharge in a sealed flask to see if it would start to generate the kinds of chemicals found in living things. It succeeded, even though it was a flask rather than all the oceans of the world and it only lasted a fortnight rather than millions of years. This is a little unfair because life may have arisen in smaller pools rather than the whole ocean, but it does demonstrate that the conditions thought to exist in Earth’s early atmosphere probably could’ve generated life. The only carbon compound in the mixture was methane. I’ve suggested that the experiment could be repeated with silane instead of methane to see if silicon-based compounds developed, but the answer is almost certainly that this would just produce silica plus a few other rather uninteresting molecules like silicon nitride. Nothing like living things, even their silicon-based equivalents.

The relative paucity of silicon compounds in the interstellar medium along with the probable failure of a silicon-based alternative to Miller-Urey, which to be fair is hampered by using water rather than ammonia, strongly suggests to me that whatever else might have arisen directly from non-living matter in the Universe, silicon-based life is not going to be one of them. It might seem unfair to say that it should be conducted with silane and water rather than ammonia, but water is the most common compound in the Cosmos. On the other hand, it might all be frozen, which would give it a better chance as then it’s basically just another kind of rock.

My conclusion to this particular bit is what I hope will bring me back to the mirror life issue. I think that investigating the possibility will reveal two apparently contradictory facts:

1. Silicon-based life can never arise in the Universe of its own accord, but carbon-based life can, fairly easily, provided there’s also enough phosphorus.
2. Silicon-based life is completely viable.

What I think, basically, is that any silicon-based life of the kind I’m talking about right now is absolutely possible, but that it would have to be built deliberately through technology in a carefully controlled and isolated environment. It would need special nutrients to sustain it, would be immediately killed by Earth’s environment due to being far too hot, having free oxygen and water vapour or water, break down due to ultraviolet radiation in sunlight and it would also lack essential nutrients and “starve”. But all of this is good, because if viable silicon-based life can exist and be used to manufacture drugs or other substances, it could do exactly the same thing as mirror life but would pose much less risk to the life already here. In fact, it could even be mirror life and still be harmless.

Right now, I only suspect silicon-based life of this kind is practicable. There are similar silicon compounds to fixed oils, alcohols and even possibly DNA. An experiment was once performed with somewhat more complex compounds than in the Miller-Urey experiment, and it led to the formation of microscopic spheres able to separate their contents from the outside world, and also to bud, divide and form strings. Without any means of storing a genome, to me it seems entirely feasible that the more oil-like silicones could do the same, although in this experiment polypeptides were involved rather than lipids. All sorts of structures in living cells are made from lipid membranes, such as the cell membrane itself, the nuclear membrane, lysosomes, mitochondria, chloroplasts, the Golgi apparatus and endoplasmic reticulum, so in other words, most of the structure of the cell. All that’s missing is something to make it go.

I personally suspect that amphiboles could replace nucleic acids such as DNA. The best-known amphibole is asbestos, consisting of pairs of silicate fibres bonded with each other along their lengths. This structure is quite similar to DNA of course, but is more homogenous. This is in the boring and ordinary area of silicate chemistry and mineralogy, so the basic unit is a tetraheral molecule with four oxygen atoms at the vertices and a silicon one at the centre. Chain silicates, of which amphiboles are more complex examples, are repeated silica units sharing oxygens along one dimension of their vertices. Or rather, those are simple chain silicates, also known as pyroxenes. Spodumene, the main lithium mineral and therefore economically, politically and technologically a very important compound, is a simple chain silicate. The alignment of each unit varies cyclically along the chain. In other words, they’re kind of helical, like DNA. The presence of lithium and aluminium in spodumene also shows that other elements can participate in these structures. Because of their fibrous structures, pyroxenes and amphiboles cleave easily parallel to the orientation of their chains. However, the links between the chains of amphiboles are simply shared oxygens at the corners of adjacent tetrahedra between the chains, meaning that they themselves are not helical. Spodumene’s lithium and aluminium ions are in the spaces between the oxygens of the tetrahedra.

This, then, is my first proposal for a substitute for DNA, intended to bear information for genomes: an amphibole with interstitial ions of at least two different metallic elements. If only two are used, the storage becomes binary rather than the more sophisticated four-base arrangement in DNA, meaning that the number of units needed is higher per bit but the actual scale of the chains is considerably smaller than those of DNA despite silicon atoms being larger than carbons, so there’s a compensation here. I am assuming, and here I haven’t put any work in I’m afraid, that this DNA substitute can come unravelled and be transcribed like real DNA. There would also then need to be some analogue to transfer and messenger RNA and in particular ribosomes for the production of protein analogues, and this in fact may be the missing link.

There are so-called “unnatural” amino acids which contain silicon. However, well, I should probably talk about protein-forming amino acids before I go further. An amino acid is simply an organic, i.e. carbon-based, acid with the usual carboxyl (COOH) group at one end and an amine (NH₂) at the other and at least one carbon between them. The simplest is the aforementioned glycine, which is non-chiral and just has a hydrogen on each side occupying the otherwise free bonds of the central carbon atom. Other protein-forming amino acids have different side groups, hanging off one side replacing the hydrogen, of which the most important are the few sulphur-containing amino acids which can link sideways to other amino acid molecules and form proteins into more complex shapes than just plain chains. Amino acids generally join when a water molecule forms from the OH of the carboxyl and an H of the amine groups. Now there are silicon-containing amino acids, but the silicon in question is in a side group and not part of the chain. A fully silicon-based form of glycine can exist but only as a gas, and quickly breaks down in a biological-type environment containing water, and it can also be seen that the formation of a water molecule between the two ends of amino acid molecules would immediately destroy any possible protein analogue. This leaves aside the issue that organic acids are based on carboxyl groups, not an analogous silicon-based group which doesn’t actually exist. It might, however, be possible to synthesise chains of amino acid-like units in a “just in time” sort of way where they bond immediately after being formed, even with carboxyl-like groups, and this is in fact how some cyclic silicon compounds are manufactured. These are not, however, large molecules although they are worth looking at more closely later on.

So that doesn’t at first sight look very promising. However, maybe this is looking in the wrong place. Siloxanes tend to be thought of as more like rubbers or oils than proteins or peptides but in fact they may be approximate substitutes for proteins as, structurally speaking. They’re basically silicones, as I understand the word. They resemble proteins in the sense that they are chains of monomers with oxygens bridging the gaps between the units, whereas proteins use nitrogens for the same purpose. Siloxanes also have side chains or groups which modify their properties. With oxygen, and it should be remembered that once silicon is bound with oxygen it’ll be very difficult to separate it again, silicon compounds are then able to form more versatile compounds, with more complex rings and chains which are stronger than just silicon on its own can form, precisely because of the strength of such bonds.

Actual rubber, latex, gutta percha and in fact many other phytochemicals, is made of isoprene units. These are worth looking at because they are extremely versatile and compose all sorts of familiar things such as many of the components of essential oils. Although they’re nowhere near as versatile as amino acids, it’s still possible to make quite interesting molecules out of them. Siloxanes are similar in this respect. The advantage of silicone rubber over isoprene rubber is that it is solid over a much wider range of temperatures without hardening or becoming much softer, and because that range is larger the middle of that range is also larger and it tends to be very stable in its physical properties over a wide range of temperatures. This means it’s less likely to perish. Unlike carbon-based organic compounds used for similar purposes, silicone rubber used in electronic circuits doesn’t become conducting when it breaks down, which is also useful as electrical properties need to remain quite stable. They’re very water repellant because they have methyl groups on the side chains and therefore interact with their surroundings like hydrocarbon oils. This does of course mean they contain carbon, but they vary a lot according to the size of the molecule from apparently water-like liquids to thicker oils and greases, and are used in shoe polish, to seal masonry against water penetration and to prevent foaming in sewage. They’re also non-toxic, which is important bearing in mind that the point of what I’m pursuing here is a less hazardous alternative to mirror life. Silicone rubbers are the next stage up with molecule size, and beyond that are the silicone resins, which resemble bakelite and used to make circuit boards and non-stick coatings.

All of these, though, need to be synthesised initially using energy levels higher than those found in biochemical reactions. They can’t be made using a silicon-based cell-like entity and if they were going to be used at all, they’d need to be supplied as nutrients. Nonetheless, taking all these things together it does seem plausible to me that some kind of silicon-based artificial life could exist using this route, particularly bearing in mind that chemistry has been developed by carbon-based life forms in a water-rich and highly oxygenated environment, and in fact the biasses are apparent, for instance in definitions of acids which rely on solutions of water rather than some other liquid. I think naively that there’s probably a lot of silicon chemistry we don’t know about. All of this, then, supports my contention that silicon-based life cannot arise on its own but could exist in highly contrived environments supported by technology and carefully controlled, which is in fact exactly what we need.

3. Hybrid Solutions

But all this is not the only way silicon can be extensively involved in biology. Another way in particular occurs to me, and there’s also a third and possibly even a fourth. Silicon is in fact used in many organisms. For instance, there are sponges whose skeletons are made of silica and protozoa who live in silica shells, and of course diatoms. In all such cases, silica is involved and is composed from the rather elusive silicic acid. Silicic acid’s very existence has been debated in the past, and has unexpected parallels with carbonic acid. Carbonic acid is, in biochemical terms, simply carbon dioxide dissolved in water, but in chemical terms there’s a real substance which can exist in the absence of water and is stable at room temperature, and is a gas. Silicic acid is similarly nebulous but for different reasons. Acids are often thought of as the hydrides of the corresponding “-ate” or “ide”, so for instance sodium chloride corresponds to hydrochloric acid and calcium sulphate to sulphuric acid. By this token, bicarbonates, i.e. hydrogen carbonates such as sodium bicarbonate, ought to have a corresponding carbonic acid and silicates a silicic acid, and there’s certainly something going on but it’s not the same thing and their existence in both cases is marginal. Carbonic acid seems to amount to carbon dioxide dissolved in water, and is essentially fizzy water in higher concentrations, but also exists as a literal subliming compound, not an acid because it isn’t in the presence of water, where it will tend to dissociate. The bicarbonate ion is central to pH balance in the body, but doesn’t form part of macromolecules. Silicic acid “suffers” from the “problem” of crystallising into silica at high concentrations, but this means that it can be used to build structures from silica. This is far simpler than all that complex chemistry mentioned above, but also less flexible. Literally so in fact as it amounts to the formation of glass, or perhaps opal, which is hydrated silica.

It’s easy to imagine a vertebrate-like animal who has replaced some of their body with silica. Bones and teeth are very obvious examples, and others exist. When real ocular lenses develop, they persist throughout the lifetime of the animal, although they can become cloudy. These could be made of glass. Our aquatic ancestors had tooth-like scales on their skin which developed in a different process than the scales of mammals, but in principle these could be silica too. Other silicon compounds also interact with living systems. For instance, there are cyclical silicones which have endocrine action or are endocrine disruptors. This is obviously a bad thing, particularly when you realise they’re used in cosmetics and toiletries, but it does indicate that there are silicones which could in theory completely replace certain hormones in the body, although the body couldn’t make them itself. That puts the animal in a similar position to any animal having to obtain its vitamin D from food rather than producing it themselves, so if it could actually exist in the environment it could have that function. There are also other functions in the body which could be performed by silicones, such as the cushioning, though not the calorific, function of adipose tissue, the barrier function of skin and the lubricating nature of sebum, mucus and synovial fluid within joints, but all of this would have to be available from outside, so once again the substances would in some form have to be available from the environment. This second version of silicon-based life would have a “core”, as it were, of carbon-based compounds and processes such as DNA, RNA and proteins, which are able either to assimilate or synthesise silicon compounds, but the fact remains that the energies required would have to be very high unless practically everything already existed. If we’re talking synthetic life, this makes the organisms in question assemblers from materials which have already been produced, but this is still useful. However, unlike the previous example, these organisms could still constitute a hazard which could spread to some extent like mirror life might.

There are two further possibilities that I can think of. One is the very common, almost clicheed, idea that computers are silicon-based life. Maybe they are, although it might be more accurate to think of them as complex non-living structures. On the other hand, maybe they could be designed to be more self-sustaining, reproducing for example. This might not be desirable of course. The other is that maybe there could be mechanical life made of silicon compounds. Then again, it could be made of diamond, so the fact that this is silicon-based might depend on the physical and chemical properties of the element but not in such an involved way.

4. Ethics, Politics and Sustainability

All that said, would any of these things be desirable, ethical or appropriate? Do they have other environmental consequences? This, I think, is where it all falls down. For a vegan in particular, the issue of actually creating artificial life, even if it doesn’t involve vivisection, which it very well might, is questionable because beyond a point one is simply creating slaves, and not just slaves but organisms whose only reason for existence in terms of their very nature is slavery. This argument is similar to the GMO one, which is often expressed in terms of undesirable health or environmental consequences, but there’s a more fundamental issue here, which is that we don’t own the organisms we modify. The assumption is that humans have dominion over other life, as if it was created solely for our benefit. This argument also applies to some extent to conventional breeding, and of course being vegan I don’t think it can usually be justified although it’s possible that, for example, a dog whose muzzle is so compressed that they can’t breathe should only be bred with others with longer muzzles and so forth, so maybe.

Turning to the purest form of silicon-based life, whereas it is true that it wouldn’t survive outside its carefully designed and sealed environment, its remains could still be harmful. For instance, the amphiboles making up its genetic code would effectively be asbestos, so there could be similar health problems as are brought by nanotechnology. These are like microplastics, but smaller. Nanoparticles can enter the bloodstream and carry biological macromolecules with them as they go. They can unsurprisingly cause respiratory disease. The problems are similar to those of microplastics but less predictable and possibly even more persistent. This applies less to the hybrids than the purist version, but some of those may have the additional problem of being fruitful and multiplying outside their intended environment, though not so harmfully as mirror life. The others could still consitute some kind of dead end and would strew the land and sea with xenochemicals whose risk to the environment is often unknown but does include endocrine disruption.

I’m going to cover the next bit somewhat more broadly and talk about silicones as general use products rather than these specific cases, which are of course speculative and may never happen, but the same criteria often apply to them, though not really to the simple production of silica by existing biological processes. Silicone has often been pushed as an alternative to plastic, which sounds strange to me because I see it as a variety of plastic, but it is true that it isn’t primarily derived from hydrocarbons, i.e. coal, oil or natural gas. That said, the side chains of siloxanes are so derived, although they don’t have to be, in the same way as biodiesel is not a fossil fuel, although biodiesel brings its own problems. What is probably not eliminable is that the sand needs to be heated to 1800°C in the extraction process, and such furnaces are “always on” because they take too much energy to reheat and the only time they’re allowed to cool is when they’re decommissioned. They may also use fossil fuels for heating.

In general, and I’ve already mentioned exceptions, pure silicone doesn’t leach toxins into the environment, whereas polystyrene and phthalates do. High-density polythene is also quite innocent in this regard, by the way. However, silicone is often not pure and unless it’s medical or food grade will probably contain carbon-based plastics. However, at high temperatures such as in particularly hot ovens it can react and silica is known to cause cancer. This is a bit misleading and it depends on the size and shape of the particles, as in fact silica is present in most human diets due to the likes of diatoms in sea food and physiologically occurring silica in cereal crops. That obviously doesn’t make asbestos okay! It’s technically recyclable but in practice because most silicone products are designed for long term use this recycling is not economic and tends not to be available to the public, but there are schemes where it can be pooled and sent off by communities.

Speaking of silica, this has its own environmental footprint, and to cover this it’s worth talking about the silica cycle. Some silica is biogenic, i.e. made by organisms such as diatoms in particular, and is also able to sequester carbon as the carbonate and silica cycles are linked. Carbonic acid formed in rain dissolves small amounts of silica from rocks, washing silicic acid into the sea where it’s concentrated by organisms who use it to compose parts of their bodies such as glass sponges and diatoms. Their silica sinks into sediment and is dissolved back into silicic acid. On the land, similar processes take place but much more slowly and on a smaller scale. This means that wholesale removal of silica sand from the sea or land is not a good idea if it occurs at a greater rate than replacement, which is slow. This also disrupts the food chain as diatoms and other silica-using single-celled organisms can’t produce as much due to less silicic acid in the water. Sand removal can also lead to flooding, and mining basically always damages the environment – it’s unfeasible not to.

5. Conclusion

In the end, the risks of mirror life are much greater than those of artificial silicon-based life if the latter is possible, but the second is definitely not without its dangers. It amounts to nanotechnology, and there’s a second issue regarding the politics and ethics of creating life which is necessarily enslaved to human, or possibly AI, whims, which to my mind overrides the practicality. Whether or not this alternative is possible, it may not be appropriate as we already know that various high-tech inventions and materials are paralleled in the living world and therefore can be produced in an entirely environmentally friendly and sustainable way. From another angle, if we are the only carbon-based life forms who have ever existed, there will be no silicon-based ecosystems anywhere in the Universe because the conditions allowing them to arise are so highly contrived. However, other possibilities exist, including the existence of alien mirror life, and it would be catastrophic for us to come into contact with it, for both it and ourselves. In the meantime, there are better solutions to our needs.

As I said, it’s been suggested that I turn this into an academic paper, so I apologise for all the waffle. I really don’t think it should become one and as I say, it isn’t my field, though if my life had gone differently it probably would’ve been. The best outcome for this is that it gets absolutely trashed by someone who knows more about all this than I do, so go on, do your worst. I’m waiting.

DNA – Douglas Noel Adams and Deoxyribonucleic Acid

I’ve recently had a kind of brainworm I had to get down on paper, or rather on screen as it is nowadays, though it needn’t be. It focusses on ‘The Hitch-Hiker’s Guide To The Galaxy’ and I have of course spent way too much time concentrating on this to the detriment of the work itself, but I can’t resist it. On this occasion though, it yielded fruit, almost literally in fact, and turned out to culminate in something which was a lot less ridiculous than I initially thought. The problem was that despite it not being particularly pointful, I couldn’t get it out of my head.

The ultimate question, so to speak, is this:

How many species of organism could be rescued from Earth after it gets demolished by the Vogons?

This thought originated from the scene in Fit The First where Ford and Arthur are hiding on the Vogon spaceship, having just beamed aboard, and after a suitable pause, Ford tells Arthur, “I brought some peanuts.” When I heard this line, I felt a sense of poignancy that not only had the world just ended, but apparently the only other species of Earth life than humans which persisted, the peanut, would shortly itself be destroyed by Arthur’s digestive juices, and then that would be it: nothing would remain other than Arthur, as far as the listener knows at the time. Further consideration, and further listening, would demonstrate that this was not in fact so. And so begins the highly elaborate glass bead game.

There are, considering the entire trilogy of five books, several categories of life originating on this planet involved. It breaks down thus, and I am going to number the categories because they are quite enlightening:

1. Trillian and Arthur themselves. Humans survived the destruction of the planet.
2. Organisms whose DNA or other biological traces are on or in Arthur, or stand a chance of being associated with him.
3. The same issue considering Trillian. It may seem arbitrary to cleave the two humans in this way, but it turns out to be anything but. I’ll come back to this.
4. Other organisms who left Earth before or during its destruction, either canonically or plausibly without evoking the canon.
5. Earth organisms who canonically sprung into being due to the operation of the Infinite Improbability Drive.
6. Organisms accidentally removed in other ways.
7. Organisms mentioned which appear to be from Earth but in fact are not.

I’m going to consider these in reverse order.

Organisms Only Apparently From Earth

Items are mentioned here and there whose origin appears to be terrestrial but is apparently not. For instance, Ford asks the Vogon guard whether the appeal of his job is wearing rubber. Rubber could be considered as originating only from a specific tree originating in Brazil, Hevea brasiliensis, the rubber tree. However, two facts argue against this. One is that latex from other plants can and has been used to make rubber, for instance dandelions. The other is that synthetic rubbers exist and the word could be used less strictly, and may well be. For instance, there is silicone rubber. Hence rubber itself probably shouldn’t be taken to indicate that there are rubber trees of that species elsewhere in the Universe.

This is in fact kind of acknowledged in the books, with the existence of jynnan tonix and ouisghiansodas. Many civilisations throughout the Galaxy have a drink called something like “gin and tonic”, although beyond the name they don’t resemble each other, and it also turns out that there’s another similar coincidence, undiscovered and unacknowledged, in the form of “whisky and soda”. Given this, it’s possible that the various items referred to are not identical to an Earth reader’s concept of those things. They may in fact be almost but not entirely like them. The obvious answer here is tea, as produced by the Nutrimat Machine. It isn’t clear where this originates. Tea is available from the local megamart in a variety of easy to swallow capsules, and the initial creation of the Infinite Improbability Drive required a cup of really hot tea. It isn’t clear why, because hot water might be thought to suffice. Arthur is also made the best tea he’s ever tasted at one point on the Heart Of Gold. Hence for some reason, tea appears to exist, or to have existed in the past, elsewhere in the Universe. However, like rubber the word “tea” has a more generic meaning, referring to any vegetable matter infused in hot water, such as chamomile tea or rooibosch. Even so, Arthur clearly perceives the tea as tea. Two things may have happened here. Either literal Camellia sinensis exists on other worlds or it was obtained from Earth. There is a third possibility which will be considered later.

One fruit is mentioned at least thrice. The Pan-Galactic Gargle Blaster is described as having one’s brains smashed out by a slice of lemon wrapped around a large gold brick. When Ford and Arthur arrive on the ‘B’ Ark, the security guard offers them a lemon with their jynnan tonix. Finally, on Brontitall, the starship is delayed nine hundred years while waiting for lemon-soaked paper napkins. This is quite a striking recurrence. It’s possible that the lemon arrived with the Golgafrinchams on the ‘B’ Ark, but perhaps interestingly the scent of lemon is quite widely distributed through plants on this planet, such as lemon grass and lemon verbena. It’s one of two enantiomers of limonene, the other being the scent of oranges. There are also other lemon-flavoured organisms, such as black ants. The presence of citric acid in an organic life form would probably not be unusual. For whatever reason, something lemony is out there among the stars. Perhaps even a lemon.

Potatoes seem to be another such organism. These are very ancient. The Silastic Armourfiends were ordered to punch bags of potatoes to vent their aggression many millions of years before the manufacture of Earth and therefore the appearance of potatoes as we know them. Again, this could be a generic reference to tuberous root vegetables. Even on Earth we have starchy root crops similar to potatoes, such as sweet potatoes.

A further species, possibly several, crops up in Deep Thought’s original deduction of a recipe for rice pudding. This includes rice, milk, cream and cinnamon in the TV version. The existence of rice is not controversial. It means that rice pudding existed at that point in time. To digress slightly, it’s difficult to know how to refer to deep time in H2G2 because in its universe Earth didn’t exist before a few million years ago, so it’s not sensible to use the conjectured geological time periods such as “Jurassic” before the planet was built. The only real epochs are the Pliocene, Pleistocene and Holocene, the only real era is the Cenozoic, and not all of that. The question regarding Deep Thought here, though, is whether it anticipated the existence of rice pudding or deduced its current presence in the Universe. If it did the former, there’s an issue with why it couldn’t simply use its anticipation of the future course of Earth history to give the mice the Ultimate Question, so it makes more sense to see it as already in existence. The existence of milk in this recipe is pretty unproblematic, as milk is just what we call opaque white potable liquids such as coconut milk, and sometimes even impotable ones such as dandelion milk. Cinnamon, however, is highly specific.

It’s possible to extract a principle from this: there are generic items in the wider Universe which have surprisingly specific resemblances to familiar terrestrial ones. Out there in the Galaxy there is milk and rubber, perhaps unsurprisingly, but also tea, potatoes, lemon and even cinnamon. Incidentally, I have to get this out of my head: the spice Melange from Frank Herbert’s ‘Dune’ series has similarities to cinnamon according to the now-banned Dune Encyclopedia, so it isn’t just H2G2 which anticipates the existence of interstellar cinnamon (brand new sentence there). There are two other aspects to this. In an infinite Universe, everything is possible according to the Guide, so for example the Babel fish and ratchet screwdriver trees exist, as do sentient mattresses. Just on the last issue, it is kind of true even on Earth that living mattresses and lilos are possible as they did before the evolution of life as we know it since the Cambrian. This means that every species found on Earth does in fact exist somewhere else in the Universe, and in fact that a carbon copy of Earth exists which was not built by the Magratheans. Maybe we’re on that Earth and Arthur Dent’s an alien. The other aspect is that Deep Thought could have designed Earth as a microcosm of the wider Galaxy with organisms resembling those from elsewhere, so it isn’t that there are coincidentally or by convergence life forms elsewhere so much as that they were deliberately put here.

Organisms Accidentally Removed in Various Ways

The main mechanism here is teasers, or as we call them, little green men. These are occupants of interstellar craft who visit Earth and other planets and pretend to be stereotypical aliens. They are presumably also abductors, creators of crop circles, and interfere with cattle. I’m going to assume that the most contact they have with organisms on Earth is in the form of trampling on crop circles, which I also assume they make in the same way as the hoaxers do. Incidentally, although crop circles and UFOs were not widely associated by the public until something like 1990, the association did exist back in the ’70s but was only made in flying saucer enthusiast circles, so to speak. This is of course leading up to the “fact” that teasers take wheat pollen with them when they leave – Triticum aestivum. There’s another aspect to their visit which I will consider under another heading as it’s best considered with Trillian and particularly Arthur.

When the Earth explodes, various particularly tough organisms such as extremophiles might survive in the ensuing cloud of débris. Tardigrades are the obvious example, as they can survive dormant in space, possibly for years. There may even be tardigrades on Mars, and there definitely are on Cynthia (“the Moon”). Another category of organisms this clearly applies to is certain archaeans. Archaeans are microörganisms once confused with bacteria, many of which can survive in extreme conditions such as hot springs. These could possibly survive too, again perhaps in a dormant state.

Zaphod Beeblebrox also visited Earth and took one organism, Trillian, with him deliberately, but probably also took others accidentally. I’ll go into this in greater depth when I consider Trillian.

Finally, Arthur finds an unexpected bottle of retsina:

Vitis vinifera – grape. Used in the retsina Arthur finds on Agrajag’s planet.

Pinus halepensis – Aleppo pine, whose resin is an ingredient of retsina.

Saccharomyces cerevisiae – Brewer’s yeast, found in the retsina.

Infinite Improbability Drive Creations

Several organisms are created when the Infinite Improbability Drive is operated. There are very obvious examples, but I’ll deal with them in order of the timelike curve described by the Heart Of Gold.

The first time the drive is operated, it causes two hundred and thirty-nine thousand fried eggs to appear on the planet Poghril, where all but one person had just died of starvation. This seems at first to imply that it brought Gallus domesticus into existence, but actually it doesn’t. Eggs are a common means of reproduction found throughout the metazoan clade, such as with slugs, spiders and birds. These particular eggs must resemble hen’s to some extent because they seem to contain albumen and yolks and are altered by frying in a familiar way. At no point did they have shells, incidentally, as they were yanked into being without them. They are also high in cholesterol. Even so, I don’t believe these have to be hen’s eggs.

Now for the two most prominent incidents. When Ford and Arthur are rescued, they meet several species of animal on the Heart Of Gold and Ford turns into a penguin. I’m not sure whether to count that because he’s only temporarily transformed. There’s also a five-headed person crawling up a wall, but there are no such organisms on Earth. What there is, however, is an infinite number of monkeys, apparently capuchins. It isn’t clear what happens to any of these species but they don’t seem to be in evidence once normality is restored. That’s not true, though, of the sperm whale and the bowl of petunias. This next bit, therefore, is easy: Petunia and Physeter catadon. There’s even flesh strewn around on Magrathea afterwards. Although it’s straightforward that these species are brought into existence, it’s not so clear that they were alone. The sperm whale could, for all we know, be encrusted with barnacles and contain typical gut flora for a sperm whale along with parasites such as a tapeworm, but the simplest assumption is that the sperm whale is isolated. It’s also fair to question which organisms if any co-occurred with the Petunia, since it is in a bowl and therefore potted in some material. However, again we don’t know that this is so.

Just a side-issue on this: there was at one point going to be a goat on the Heart of Gold after Arthur rescued everyone from the missiles, but this was not pursued. On other occasions, there was a fossilised towel, but nothing is recorded to have happened in that respect when it was operated to escape from the Vogons or visit the Man In The Shack.

There is a flaw in how I’ve considered this. In fact, any terrestrial species could be conjured into existence by the Infinite Improbability Drive, but not in the narrative of the actual stories.

Trillian

Trillian is the most interesting aspect of this entire issue, and in fact she’s why I decided this wasn’t just a frivolous mind game. There is a markèd contrast between Arthur’s and Trillian’s biomes due to the circumstances of their departure and gender, which could in any case be linked.

Trillian was at a party six months before Earth’s destruction. She was surrounded by various alcoholic beverages and snacks. This contributes to her status as a goldmine of genomes, as does her gender presentation. Unlike Arthur she’s likely to have cosmetics, scent and jewellery, as well as residues of toiletries. She was being chatted up by Arthur, then Zaphod, as “Phil”, came along and, well, abducted her right out of that environment, which was not the moribund ecosystem surrounding Arthur as it was being destroyed, but a still-thriving habitat. Many organisms are likely to be held in common between them such as Candida albicans, which is found in the human gut, and in fact many of the microörganisms in their digestive tracts, lungs and body surfaces. Both have, for example, follicle mites – Demodex follicularum. They may also have pathogens, such as rhinovirus, and at a pinch even the likes of fleas and head lice, though probably not. Both have Mentha x piperita – peppermint – in their mouths, or possibly spearmint, from toothpaste.

Here’s a breakdown of what she might distinctively have on her and why:

From cocktails:

Cinchona pubescens – quinine, in bitter lemon.

Juniperus communis – juniper, in gin.

Olea europaea – olive, on cocktail sticks. This is, however, also mentioned in connection with Pan-Galactic Gargle Blasters, so it doesn’t count as distinctively terrestrial.

Prunus avium – cherry, also on cocktail stick.

Curcuma longa – cucumber. This is a long shot but not only might this occur in a cocktail but also in a cucumber sandwich. That also means:

Lepidum sativum – cress.

Sinapis alba – white mustard.

(Mustard and cress sandwiches)

Possibly an Abies species for the cocktail stick, but more likely to be Pinus, which was already in the retsina.

Artemisia absinthium – wormwood, if they had absinthe.

Gallus domesticus – hen, if there was advocaat (eggs).

Vanilla planifolia – vanilla orchid, same source.

Citrus aurantium – orange.

Pyrus malus – apple.

Angostura trifoliata – if they had genuine angostura bitters.

Solanum lycopersicum – tomato.

There would also have been snacks, which might allow various nut species to be recovered, such as Anacardium officinale (cashews), Prunus amygdalus (almond) and others. There could also be other things such as trail mix, pork scratchings or Bombay mix, but it would rely on Trillian actually eating it, and having the drinks.

Canapes might contain:

Salmo salar – salmon

Thunnus tynnus – Atlantic bluefin tuna

Allium sativa – garlic

Again, she’d have to eat or at least touch these. Both these categories are very uncertain, and in fact I can add a couple of quite likely ones:

Ananas comosus – pineapple. There are pretty sure to be pineapple cubes on sticks at this party.

Prawn cocktail – it isn’t clear to me which species of decapod is most popular as food.

Much of the above is culturally and historically specific. Wealthier people would have different food available. Trillian is not wealthy, but on the dole, although she may have had social capital from university days or others. Later on, something like sambuca might have become available, meaning licorice, possibly elder (Sambucus nigra). There is a positive wealth of possible organisms here, but also a high degree of uncertainty.

Cosmetics: Many cosmetics are mineral-based. Their ingredients also change over time, trending at the moment towards plant sources.

Lipstick:

Ricinus communis – Castor oil plant.

Theobroma cacao – cacao. Cocoa butter.

Simmondsia chinensis – Jojoba (also possibly in shampoo and conditioner).

Copernica conifera – Carnauba wax. Could also be on lemon rind.

Dactylopius coccus – cochineal insect. Could also be present in food.

Kerria lacca – lac bug. Possibly in makeup or on lemon rind, might also be on nail varnish.

These last two are likely to be less common today.

Eye shadow: exclusively mineral ingredients.

Mascara: big overlap with lipstick.

Foundation: palmitic acid, which remarkably at this stage (1978) could have been from sperm whale again!

Various glycerol-based lipids from a variety of different sources.

Primer: again remarkably, this could in theory be a source of Thea sinensis or Vitis, but I reckon that’s too sophisticated for the ’70s. Another change.

Blusher:

Cetorhinus maximus – basking shark, source of squalene. Could be a couple of other species. Nowadays this is not from animals, but back then it was. There are other species of shark this could be from.

Shampoo:

Cocos nucifera – coconut palm. TBH, this is probably going to be in something on the above lists anyway.

Elaeis guineensis – oil palm. This doesn’t really belong here but there will be palm oil in something.

Conditioner:

Sorbitol occurs naturally in various fruits.

Perfume and scent ingredients derived from various plants, e.g.

Lavandula angustifolia – lavender

Rosmarinus officinalis – rosemary

Rosa sp – there are so many species of rose it’s ridiculous, so I’m not going to narrow it down further than that.

Jasminum officinale – jasmine.

Pogostemon cablin – patchouli (less likely).

It’s uncertain whether these are just various compounds from the relevant organisms or if their actual genomes would be available. It’s also notable that Trillian has a less detailed back story than Arthur, and some of the uncertainty may result from that. This, sadly, probably arises from Douglas Adams’s sexism. His female characters generally seem to be less filled-out than his male ones. Most of his cybernetic characters are also male, with the exception of the Nutrimatic machine. The type of character Trillian has been made to become is, to be fair, not enormously stereotypical because she’s an astrophysicist, but her presentation is typically feminine, hence the massive biological accoutrements. This could be flipped: why isn’t Arthur expected to make this effort? It’s still interesting that if you remove an average woman from 1970s Islington from Earth, you sample a lot more of the planet’s biosphere with her than if you remove an average man from the rural West Country, even though she’s in an urban environment and he’s in a rural one.

Arthur’s turn. Arthur is a six-foot tall ape descendant (nowadays he’s seen as an ape) who works in local radio, and is of course a man. Here’s a list of what he has on or in him at the end of the world:

Felis cattus – domestic cat. When Arthur arrives back on Earth, there is a dead cat in his house, so he may have had a cat. Some fur may exist on his dressing gown. In fact it almost certainly does, and also aerosols from the cat licking her fur. 

At this point I should probably mention an organism of ‘Trainspotting’ fame: Toxoplasma gondii. Arthur may well actually be subclinically infected by Toxoplasma, as many people associated with cats are.

Canis familiaris – dog. As Arthur is about to be thrown off the Vogon spaceship, he says he was planning to “brush the dog”, so there may also be dog hairs on his dressing gown. Also, possibly Know-Nothing may have done the same, though this is less likely. In case you don’t know, Know-Nothing is the pub dog in Cottington, Arthur’s village.

Right at the start of the narrative portion of the story, Arthur’s morning routine is described.

Bos taurus – cattle. Arthur makes himself a cup of coffee just before he notices the bulldozers outside. The milk he puts in it probably has cow DNA in it.

Coffea robusta – coffee. Since it’s the ’80s, Arthur probably uses instant coffee, hence robusta rather than arabica.

Toothpaste occurs around this stage. There’s also shaving foam, which may contain Gossypium among other ingredients, and there might even be aftershave although this isn’t mentioned.

Humulus lupulus – hops in the six pints of beer Ford buys Arthur at lunchtime.

Hordeum vulgare – barley used to make the beer.

Saccharomyces cerevisiae – the yeast fermenting the beer and the retsina on Agrajag’s planet, which I’ve mentioned.

Arachis hypogaea – peanuts. “I brought some peanuts” – Ford’s comment which started this whole futile enterprise.

Musca domestica – house fly. Arthur swats flies on prehistoric Earth, possibly not that species but at least one species of fly. This is also Agrajag.

Oryctolagus cuniculus – the rabbit Arthur killed to make his bag out of. Also Agrajag.

Ovis aries – sheep. Wool in dressing gown.

Tineola bisselliella – clothes moth. Possible but unlikely.

Gossypium arboreum – cotton, probably present somewhere on Arthur’s person.

Morus alba – again, possible but unlikely. The white mulberry on which the silk worms making any silk Arthur might be wearing fed.

Bombyx mori – silk worm/moth. Could be present in Arthur’s clothing

Hevea brasiliensis – rubber tree. Might be present in Arthur’s slippers.

Saccharum sp – sugar cane. Unlikely, but he might’ve had sugar in his coffee and that might not have been refined.

Beta vulgaria – sugar beet. Mutually exclusive with the previous species. Also, I’m not convinced white sugar still contains any trace of DNA.

Commensal organisms:

Demodex folliculorum – follicle mite in Arthur’s eyelashes.

Candida albicans – thrush yeast. Present in the gastrointestinal tract of about half of human adults.

Gut flora – a large number of species.

Dermatophagoides pteronyssinus – house dust mite. According to the Infocom game, Arthur has fluff in his pocket, which probably contains this animal. Incidentally, this is the European dust mite. The American dust mite would not have survived in all probability.

Hence Trillian could be associated with thirty-seven named species whereas Arthur, despite the fact that we know a lot more about his circumstances as he left Earth, only has twenty-five. Two of them result from his personal violence against animals.

Arthur may not be wearing make up, but he is wearing mud. He lay down in front of the bulldozer. This means he’s likely to be covered in it, leading to such soil organisms as Caenorhabditis elegans and Colpoda, as well as various fungi.

Ford and Arthur are also covered in pollen. This would vary according to the time of year. Perhaps surprisingly, there are only two short date ranges during which the destruction of the Earth could have occurred. We know from the TV series that the Sun rose at 6:30 am on that day. Due to leap years, the date when this happens moves around slightly and due to BST it might be an hour earlier. We also know it’s a Thursday, although this has been disputed because of the football reference. Assuming it’s 1978, the relevant dates are 6th August (Hiroshima Day, rather appropriately), 3rd May and 4th April, none of which are on Thursday. Considering it’s the Vogons, I like the idea that it’s the last day of the tax year, 5th April. If this is so, likely pollens include alder, elm, willow, birch, ash, and, perhaps surprisingly, rather few herbs. Hence the rather obvious privet hedge buffeted by the wind just before Ford activates the electronic thumb is not shedding pollen and hence would only survive if one of its leaves got lodged in Arthur’s dressing gown or PJ’s. Some other plants would already be shedding but not at their peak, including plane, oak and canola.

Other Organisms Leaving Earth Voluntarily

There are two other types of animal who left Earth or were unaffected by its destruction. One of these was the dolphin. It isn’t clear whether this means all dolphins or a limited or unique species. I’ve assumed it was Tursiops truncatus, the bottlenose dolphin. They left Earth shortly before the Vogons arrived, having failed to be communicate the warning although I’m not sure what we could’ve done to prevent it really. They may have taken a food supply with them or simply had half-digested fish in their digestive systems, so that would include herring, mackerel and possibly krill. Other species include mullet, cephalopods, conger eels, hake, bandfish (in this case I didn’t know those existed in the first place) and porgies. Regarding internal parasites, there’s Cryptosporidium, a protist, Ascaris, a nematode, Giardia, another protist and Nasitrema, a trematode, but the question arises of whether the dolphins would use the opportunity to rid themselves of these or perhaps recognise their role in their health, as they might reduce the prevalence of autoimmune conditions. Whale lice would also be present if they chose to keep them. Just as humans are covered in pollen, dolphins and their prey are covered in phytoplankton, such as diatoms. Hence various single-celled algae can be expected to be salvageable.

The final category appears to be mice and the organisms associated with them. Again, it isn’t clear whether it’s just Mus musculus or several species of mice involved. I’m going to assume the former, but note also that whatever the original mouse was, they had time to evolve. What we think of as mice are of course merely the three-dimensional projections of hyperintelligent pan-dimensional beings, and being mice is just the day job.  Nonetheless, Trillian took her mice with her and can therefore be presumed to have taken their food. Mice are of course omnivorous, like most or all rodents, but are sometimes assumed to be herbivorous. In 1978, mice were fed a mixture of seeds and pellets of some kind which I couldn’t identify but may have been minced up insects or something. The seeds included sunflower, split peas, lentils and presumably peanuts. Mice get parasites like dolphins and humans but it’s unlikely Trillian’s would have any. It’s hard to know whether to count mice as native to Earth in the H2G2 universe, as they aren’t what we think they are.

Several issues remain. One is that Earth being only ten million years ago, all the fossils and evolution presumed to happen up until that point are fake, but after that point are probably real. I say fake evolution because DNA analysis would still show an apparent genetic relationship between, for example, humans and chimps even though chimps are native to this planet and humans are not, or between undoubtedly native organisms which were in fact separate creations or not even from the same planet or even dimension in one case. And this is the really weird thing about this whole constructed Earth scenario: Douglas Adams was clearly “a great fan of science” but his version of Earth is almost creationist, though not exactly young Earth creationist. The arrival of the Golgafrinchams led to the replacement of hominins by alien humans, since humans are aliens, and also possibly the introduction of novel species such as grapes, olives and lemons, and maybe also various other species which also replaced their native counterparts or successfully competed with species in similar ecological niches. Despite all this, all known life on Earth is now established to be related. Is this perhaps because it isn’t just life here which is related, but across the Galaxy? Did panspermia happen? Is it happening all the time? Or did the computer program which ran the Earth have to simulate the wider Universe in order to provide the right data on which to base its calculations? This could mean that Earth simply encapsulates the biomes of the wider Galaxy. Maybe life is just constantly diffusing in and out of Earth’s biosphere and linked genetically to the rest of the Universe.

To conclude, I think this is a good way of illustrating the intentional fallacy. Arthur’s and Trillian’s biomes are quite different from each other, although they overlap. Although Douglas Adams is unlikely to have any conscious intention of writing Arthur as a fuller character than Trillian, if he had written them more equally, Trillian’s biome would have been as certain as Arthur’s. This is in spite of the fact that Arthur is supposed to be “Everyman”, i.e. a close to blank slate, though quintessentially English, in whose position the reader is supposed to place herself. Trillian absconded from Earth in its prime, and because her gender stereotype is more clearly constructed than Arthur’s, she takes more of the planet with her when she goes. It’s expensive being a “girl”, meaning that whereas it’s alleged to be optional to present oneself as feminine as a woman, in many contexts this will place one at a disadvantage or put one in danger. Adams is also sketchier about Trillian’s background because he’s writing about what he knows, and he doesn’t know women in the same way as women know women. Moreover, Trillian leaves Earth willingly whereas Arthur has to be prised away from it even though he’ll die otherwise, which somehow reminds me of “women get sick but men die”. On the other hand, Trillian may be too compliant for comfort.

A few more things can be drawn out of this:

• H2G2 is oddly “creationist”, but “middle-aged Earth Creationist” rather than young or old Earth, despite Douglas Adams being proselytisingly atheist. This is also similar to Terry Pratchett’s ‘Strata’.
• Recent developments in DNA sequencing would be expected to have revealed that there was more than one line of evolution leading to organisms on this planet. Larry Niven did something similar with the Protectors.
• Terms used for certain items in the H2G2 universe are known to have wider references than they are usually used. This is acknowledged in the case of jynnan tonix and implied with ouisgiansoda, but may be much wider than is at first apparent. For instance, it may include “rubber”, “lemon” and “milk”.
• As the H2G2 universe is infinite, there are countably infinitely many identical species to those found on Earth in any case. This too is suggested in the text with the ratchet screwdriver trees, mattresses and the Babel fish.
• What would a gender-swapped version of H2G2 be like? What would this version be like told from Trillian’s perspective? Would gender-swapping include Marvin, Eddie and the Nutrimatic Machine?

My Orphanhood And Science

I’ve been very quiet on here lately due to pressure of organising things related to my mother’s death and my father’s probate, so I’m coming back to report here on a particularly affecting thought about my mother which I think illustrates something about science as it relates to feelings. But first things first.

My father died last June. One of the last things he said was a series of names of more or less binary compounds such as ammonium sulphide. I’ve never heard of this kind of thing happening before, but this is similar to something which happened with the mother of a friend recently too, whose details I don’t remember. My father had, among other things, been an industrial chemist, and we won’t know until we get there I suppose, but it seems to me that this was a sign of how firmly ingrained his scientific knowledge was in his memory that this happened. I also found it notable that this particular compound, which is used in stink bombs, has the formula (NH₄)₂S. It may mean nothing, but it does have the same initials as National Health Service. Then again, maybe he could just smell something, or was perhaps hallucinating its odour. I really don’t know.

At the end of March this year, my mother also died. They were long since divorced, so there’s probably no direct connection between these two events happening in the space of a year. It isn’t like my mother missed her husband, for example, and the differences between their ages probably doesn’t mean that anything about their lifestyle when they were together would have resulted in their deaths being close together. I could imagine that my mother still held some deep, residual affection for my father of course, but I really don’t think she did. Going down this route would probably involve imagining patterns where there are none, and this brings me once again to science, which is in a way an attempt to find out which patterns are based in reality and which ones aren’t. Given this, my late father’s recitation of chemical formulae isn’t scientific but just part of the vocabulary of science. If he’d been at all musical, maybe he would’ve hummed a tune or something similar. It is true, of course, that centuries of understanding and investigation got humanity from atomic theory in the time of Democritus and the four elements of Empedocles to a point where we understood that there were around a hundred different main types of atom which joined together through the operation of electrical forces in certain numbers to form molecules and other compounds, which are expressed through such names as “ammonium sulphide”, but the actual name of the compound is more the culture of science than science itself. It’s almost like poetry. These things can be conjoured up in technobabble by using two surnames with a hyphen between them followed by a technical sounding word, so for example the Banks-Tortora Effect, Auerbach-Gould Analysis or the Brock-Pearson Principle. These are just surnames I read off nearby books, but don’t they sound clever and technical?

All that said, real scientific findings can have real emotional impact, and my recent bereavement is no exception.

My mother was a remarkably kind and selfless person, and a non-scientific but nonetheless true way of looking at her life would be to say she didn’t deserve the misfortunes which afflicted her. A few years ago, I was casting about for a neutral way to describe what pro-lifers call an “unborn child” and what pro-choicers tend to call a “fetus”, and thought about using the term “the products of conception”. This, however, was firmly rejected by mothers I knew who had had miscarriages, and the question is still open. The words we use to describe scientific phenomena matter when they are used by people who are directly emotionally affected by them. A notorious example is the tendency for genes to be referred to by whimsical names such as “sonic hedgehog”. This is a gene found in most species of multicellular animals. Now known as the SHH gene, this encodes a signalling protein responsible for regulating the formation of organs, the central nervous system and limbs in humans, and has similarly important roles in other animals, including fruit flies. If it malfunctions in fruit flies, it produces a spiny embryo, hence the name. However, as genetics became more advanced and applied to human medicine, the gene’s name began to crop up in conversations about a lethal fetal condition known as holoprosencephaly, where the brain doesn’t separate into two hemispheres in utero, which as well as being fatal can lead to horrific facial features which I’m not going to go into. Therefore, the practice of using these playful names came to an end. When scientific findings come up against personal life, things can get distressing and upsetting.

Well, I am going to go there, mainly to show that science is not just this abstract thing which is “out there” and has no influence on how we feel about stuff.

I am my mother’s eldest child and have a younger brother. Between us, my mother gave birth to three children who were all premature but also potentially viable. In other circumstances, for instance paediatrics being a decade more advanced at the time, they would probably have survived, although each one was probably only conceived because the last one hadn’t been. This is the kind of sadness I almost feel shouldn’t be mentioned in public, and do feel shouldn’t be profited from. So I’ll state this as a cold, ruthless fact: my mother lost three babies between me and my brother. Not fetuses. Not that scientific term, and also not fetuses because of taking a position on the pro-choice/pro-life issue, but because they actually were babies. I don’t want to take away from anyone who has had a miscarriage either by denying that they too have lost a child, but I also want to assert that these were babies, born at the same stage of development as my brother, currently running marathons and living in the south of Spain with his partner, and in other circumstances it would be one of them who was doing something similarly “real person”-y today, although in that case it would be they who was my younger sibling rather than my brother. All of these are lives not lived, which ended perhaps a century earlier than they would, and which would’ve touched and resulted in other lives. But we’ll never find out because their remains are currently interred in a cemetery in Kent, and have been for over half a century. Perhaps my mother will have a memorial near them one day.

Okay, so a process of scientific enquiry led fairly recently to a surprising finding among people who had born children: some of those who had had boys were found to have XY diploid cells in their bodies, in a situation called “microchimerism”. It was found both that people whose cell lines had no Y chromosomes who had never been pregnant had no Y chromosomes in their bodies, which is hardly surprising, but that those who had had children with Y chromosomes did. This is not about sex or gender though. What this means is that cells from the fetus cross over into the maternal body and take up residence in their bodies, even in their brains, as stem cells and later develop into the appropriate cell, so for example they alter the microscopic anatomy of the brain and even participate in what is going on in that brain. It happens with female fetuses too: the only significance of the Y chromosomes here is that they happen to have indicated that something remarkable was happening with fetal cells and the maternal body. The interpretation of the fetal cells healing brain damage could go either way. It could be seen as the child controlling the parent’s mind or as a way the child is healing the parent.

The fetal cells don’t just occupy the brain. They have also been found in the pancreas, bone marrow, skin and liver. I may practically have been directly looking at my siblings when I looked at my mother. They also persist for decades, perhaps life-long. Hence it’s possible, and I choose to believe, unscientifically but still perhaps correctly, that part of my siblings was physically still with my mother until the day she died. Hence in that sense it’s possible that all of them lived into their fifties.

There’s something else though.

Another recent finding in human biology, and actually zoology in general, is what happens after an animal dies. A sketchy definition of death for vertebrates such as ourselves might be the point at which the respiratory centres of the brain irreversibly cease to respond to an increase in carbon dioxide levels in the blood. Now there are three sets of respiratory centres in the brain: in the pons, which is responsible for rhythm of breathing, the ventral centres in the medulla oblongata and the dorsal group in the nucleus tractus solitarius. It clearly isn’t a strict definition of death because artificial ventilation might keep the rest of the body functioning at this point, and clearly the rest of the brain might hypothetically continue to function even if they’ve been permanently damaged, and I don’t know if things ever happen this way round. Probably a better way to understand death would be irreversible cessation of brain stem function more generally. Note also that I’m saying “irreversible” rather than “permanent”, because permanent cessation of function may be irreversible without anything ever happening to reverse it, as with someone who doesn’t receive CPR or a defibrillator shock but might have, and therefore would’ve survived. Here again, the coldness of the scientific understanding is mixed with feelings of desperation and poignancy about someone who could’ve survived but didn’t because of the circumstances they found themselves in.

There’s a fragmentary memory here I have that individual cells from a human brain have been induced to function and divide, so presumably not neurones which can’t divide except in certain very localised regions, even twelve hours after death. This might hypothetically mean that a clinically dead body could have the injury repaired long after death as we understand it today, particularly in circumstances where metabolism and decomposition have been slowed or halted by such things as hypothermia. Maybe a body lying at the bottom of a frozen lake in winter or in a mortuary freezer, for example. But this all smacks of the bargaining stage of grief of course. The fact is that none of that now applies to my mother, who died in a hospital bed and whose corpse was still there several hours later before, presumably, being removed by the undertakers or going to the morgue.

However, there is more. Around the beginning of the twenty-first century, it was discovered that – well, I’m going to need to set out how genes work to maximise the chances of this making sense. DNA unravels and one of the strands is copied using transfer RNA, which then moves to the ribosomes of the cell and is turned into proteins. Like most processes in the cell, this requires energy, which is usually liberated from glucose and linked to the metabolic processes in the cell via adenosine triphosphate, hence my blog post ‘Sodding Phosphorus!’ a few entries back. Most of the energy liberated is helped by oxygen, which is why we need it, and of course free oxygen is not available to most of the body after someone has stopped breathing. This seems to have taken us quite a long way from the emotional side of what I’m talking about, although as I write this description I’m acutely aware than my mother did stop breathing forever a few weeks ago, so there is that. Anyway, due to the fact that most of this process benefits dramatically from the availability of oxygen, it might be concluded that it stops when someone dies. But, as I was saying, around the beginning of the twenty-first century, it was discovered that some genes continue to be expressed after death. This is known as the “thanatotranscriptome”, from the Greek “θανατος”, meaning “death”, and “transcriptome” by analogy with “genome”: all of the RNA transcriptions which occur in the internal organs of the body after death. Some of these are simply ongoing processes, but some are long since inactivated which spring back into action. This goes on for up to forty-eight hours after death. In “cold-blooded” animals it can be even longer.

Clearly cells are really complicated, and quickly break down as the carbon dioxide builds up, makes their internals more acidic and the temperature changes, usually by falling, but given that there are so many cells in the human body, not all of them just conk out immediately after death and some of those which do will have bits of their machinery still active. Significantly, one set of genes that does stop working is the suppressor genes, which are there to prevent other genes from expressing themselves and causing cancer, i.e. the oncogenes. Other genes which have stopped working seemingly permanently are the ones involved in fetal development and in the ovum. These two briefly come back into action after someone dies. Mammals, being “warm-blooded”, don’t express quite as many of these genes as, for example, fish, presumably because our bodies don’t just need oxygen but also higher temperatures than in most corpses to function, but even in us, more than five hundred genes will still be “working” out of the total genome of around twenty-odd thousand, so that’s actually more than two percent of them, which seems like a lot to me considering they’re in a dead person. Some of the genes are involved in inflammation and the immune system, which is not surprising as death is a very serious injury with the decomposition presumably being interpreted as infection. Here again I feel a sense of urgency and futility, and a kind of mixed feeling of despair that my mother’s dead body made some last-ditch attempt to defend itself against its decomposition and cried for help, as it were, which could never come. That’s grim.

This, though, was a body which had been pregnant several times, and which may, and this is not certain but I have a hunch that it did, have contained minute parts of the bodies of my dead siblings, lying almost dormant since the start of the 1970s, in the form of isolated fetal cells. In particular, considering that it is fetal genes that specifically ramp up after death, these cells would briefly, for maybe a couple of days, in a sense, and a very broken manner, resume the development which was interrupted by their untimely deaths all that time ago, and for a short period of time my mother’s other babies would in a sense be in a kind of half-living state during which they would vainly attempt to continue the development which would’ve enabled them to survive if they had been born later. In fact, considering that each time one of them was born, their chances of survival may have been higher than their elder siblings, just maybe these fatally injured cells would have in some ways reached the stage when they would have survived if they had been born. For instance, maybe there were lung cells secreting the surfactant which enables a baby’s lungs to expand properly at birth which actually had genes reach that stage and begin to manufacture that life-saving substance, only fifty-two years too late.

And then it was to no avail, because my mother’s body ended up at the undertakers, in the mortuary, in a casket, and now of course cremated, and all this in any case in an 89-year old body which had failed to stay alive.

I find this thought most disturbing. There might be things it’s better not to dwell on, but maybe if someone dwells on this for long enough in the right way, it will save lives. Even if not, it serves as an illustration of how apparently abstract and obscure scientific findings do not necessarily leave one cold if one can bring them sufficiently into focus in everyday or real life (or real death) terms. When I studied pathology, I was left with the impression that it’s primarily about the body’s desperate attempts to keep healthy from an initially very tiny imbalance that just ends up snowballing. This has a similar kind of feel to it, in that it made me sad to think of my mother’s body’s, and her children’s bodies’ including mine and my brother’s, efforts to do what they were “supposed” to do against impossible odds.

And that last bit, the realisation that some of my own cells died with my mother, means that part of me literally died with her sometime between her clinical death on 29th March and my father’s first missed birthday on 2nd April 2023.

Sodding Phosphorus!

Here is a sample of the aforesaid element:

Phosphorus has two main forms, or allotropes. When first extracted, it’s white and extremely toxic. The form illustrated above is red phosphorus of course. Left to itself, white phosphorus gradually turns into its red form, which is why the so-called “white” allotrope usually looks yellow:

By BXXXD, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1096986

This is not, however, supposed to be “all about phosphorus”. Rather, it’s about two issues which affect the element, both to do with life, one on this planet and one in the Universe generally.

I’ll start by explaining the importance of phosphorus to life as we know it. There are six elements making up most of the body of a living organism on Earth. These are carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus. Carbon is important because it can form chains and rings from which complex molecules can be built. It’s notable that even though silicon is far more abundant on this planet than carbon, life is nonetheless carbon-based. This is to do with things like carbon’s ability to link itself into chains, form double and triple bonds with other atoms, the fact that its atoms are small compared to silicon and the difficulty of getting silicon out of molecules such as silica which may be formed as a result of any putative biochemical processes. Carbon dioxide, the analogue of silicon, is a gas at fairly low temperatures and can be incorporated into other structures. It so happens that I do think silicon-based life is possible, but it would have to be created artificially and exist in some kind of closed environment whose contents were carefully selected. The chances of silicon-based life arising without intelligent intervention are very low. The greater terrestrial abundance of another element should be considered again here, but not right now. Hydrogen and oxygen are of course the constituents of water, a compound which is really unusual in many ways, such as its unusually high melting and boiling points on the surface of this planet, its ability to dissolve other compounds and the fact that it gets less dense as it cools below 4°C. These properties mean respectively that the chemical reactions needed for life as we know it can occur at a temperature where there’s enough energy for them to take place but not so much that they’d be unstable, that the compounds are in a liquid medium conducive to reactions in the first place and that the oceans, lakes and rivers don’t freeze solid from the bottom up. The two constituents are useful in their own right. Oxygen and hydrogen are components of countless compounds, including carbohydrates, amino acids, proteins and fats. Oxygen, unlike chlorine which has been considered as a possible alternate breathing gas for alien life, can form two bonds, meaning that it isn’t the dead end single-bonding atom which the halogens are. Nitrogen is a essential component of protein via its presence in amino acids. Amino acids have a carbon connected to a carboxyl group and an amino group, which can bond together to form chains, and a functional group such as a benzene ring or a sulphur atom which can have other biological functions. Proteins, in other words. There are also chemicals called alkaloids which occur mainly in plants and vary a lot, which have striking pharmacological effects, and the nucleotides are also rings containing nitrogen, encoding genes in DNA and RNA. Nitrogen is actually so reactive that it bonds strongly to other atoms, including other nitrogen atoms, and consequently it’s vital that various organisms can uncouple it and combine it for the benefit of the rest of the biosphere. This is known as nitrogen fixation and is performed mainly by bacteria and certain plants, and also by lightning, but if life had to rely on lightning to do this, it would not be widespread and nitrogen fixed by lightning would be the limiting factor in global biomasse. Sulphur is significantly found in a couple of amino acids and allows proteins to form more complex shapes as are needed, for example, by enzymes and hormone receptors, because they form bridges with other amino acids making the molecule tangle usefully together. It’s also found in hair, nails and various other substances such as the substances responsible for the smell of garlic and onions. Sulphur is actually a bit of an exception in the chief elements required for life because sometimes it can be substituted by either selenium or tellurium, and there are amino acids which have these elements in sulphur’s place, but both of them are much scarcer than sulphur.

Then there’s phosphorus. Phosphorus has more limited functions than the others but these are incredibly vital. It forms part of adenosine triphosphate, which organisms use to transfer energy from respiration to the other functions of the body. It also forms part of the double layers of molecules which form membranes and allow controlled and specialised environments to exist in which the chemical reactions essential to life take place, and also enables substances to be packaged, as with neurotransmitters. Thirdly, it forms the strands of sugar phosphate which hold DNA and RNA together, so even if it didn’t do anything else, some kind of method would have to exist to store genetic information. This is perhaps the least vital role though. A more restricted role is found in most vertebrates, in that it forms part of the mineral matrix of bones and teeth, but there’s plenty of life that doesn’t do this and the usual substances used to make hard parts of animals are silicates and calcium carbonate, among other rarer examples such as iron pyrite. Nonetheless, humans need phosphorus for that reason too, as do our close relatives. However, even the closely related sea urchins use calcium carbonate instead.

Hence several facts emerge from all this. One is that an apparently similar and more abundant element can’t necessarily be used for a similar function, assuming here that life can start from scratch. Another is that elements can get themselves into such a strongly bound state that it would take too much energy to use them for it to be worth it for life. A third is that life will sometimes substitute another element for the one it usually employs if it can. If a rare element is used, there’s usually a good reason for it.

Now the first problem with phosphorus is that it’s much more abundant inside a living thing than in its non-living environment, and the cycle that replenishes it is very slow. Phosphorus usually becomes available to the biosphere on land as a result of continental drift, the formation of mountains and erosion and weathering, and it’s lost to the land when it’s washed into rivers and the sea, where it disappears into sediment before becoming available again millions of years later. In the sea, it’s less of a problem but still a significant one because it’s only available to life as phosphates and it’s often found as phosphides instead. Ironically, there’s also an overabundance problem with phosphates in fertilisers being washed into bodies of water and leading to algal blooms, which can in fact be of cyanobacteria rather than algæ as such. Since some microörganisms can produce extremely powerful toxins, this can lead to massive marine die-offs and contaminated sea food. Where I live, a nearby reservoir was afflicted by an algal bloom and had to be closed off for quite some time, and this can also poison wildlife on land. These can also lead to high biochemical oxygen demand, which is where all the oxygen gets used up and the water becomes anoxic, which is incidentally a cause of mass extinctions, though on a much larger scale, in the oceans. This happens because phosphorus is relatively scarce and a significant limiting factor in how much life is possible in a given area, so a sudden influx of usable phosphate is likely to cause a chemical imbalance.

The Alchemist Discovering Phosphorus, Joseph Wright, 1771 and 1795.

This painting is thought to refer to the discovery of the element by Hennig Brand in 1669. Brand discovered it when searching for the Philosopher’s Stone, by heating boiled down urine and collecting the liquid which dripped off it. It turns out that this is actually quite an inefficient process and it’s possible to extract a lot more of the phosphorus by other means. The allotrope illustrated in the painting is unfortunately the highly toxic and dangerous white variety, so the alchemist is putting himself in peril by kneeling so close to the retort. The point to remember in all this is that phosphorus is found in urine, not in huge amounts but enough. This points towards a particular problem, highlighted by Isaac Asimov in his 1971 essay ‘Life’s Bottleneck’, which points out that humans “may be able to substitute nuclear power for coal, and plastics for wood, and yeast for meat, and friendliness for isolation—but for phosphorus there is neither substitute nor replacement”. Urine goes down the toilet and is flushed into the sewers, processed in sewage farms and the phosphorus from it ends up in the sea. It does gradually return to the land in biological ways. For instance, a seagull may die on land and her bones may become part of the terrestrial ecosystem, or she might just poo everywhere and return it that way, but the occasional gull or tern conking out in Bridlington is no compensation for millions of people flushing the loo several times a day. By doing this, we are gradually removing phosphorus from the land and returning it to the sea, whence it won’t return on the whole for millions of years.

Two ways round this suggest themselves. One is to eat more sea food. For a vegan, this is unfeasible and in any case fishing causes a lot of plastic pollution and is unsustainable, but of course it is possible to eat seaweed, and I do this. The other is not to allow urine into sewage in the first place or to process sewage differently. I have been in the habit of dumping urine in the garden, although I haven’t done this as much recently. It also contains potassium, and in particular fixed nitrogen, so in diluted form it is indeed useful for raising crops. However, this is on a small scale and a better system might be to process the sewage differently and put it on the land, being careful to ensure that harmful microbes and medication have been neutralised before doing so. Regarding seaweed, dulse, for example, is 3% of the RDI of phosphorus by dried weight, compared to the much lower amounts in most fish. Cuttlefish is the highest marine animal source. Human urine averages 0.035%, so you’d have to eat a lot of seaweed. However, in isolation, if you don’t, there will be a constant loss of phosphorus to the land. Guano is one solution, but not ideal and only slowly renewable.

The other problem with phosphorus follows from the same scarcity and the same use in living systems, but is more cosmic in scale, and I personally find it more worrying: phosphorus is rare on a cosmic level. In a way, all atomic matter is rare in this sense because the Universe is, as the otherwise really annoying Nick Land once said, “a good try at nothing” (apparently nobody has ever quoted that before, so that’s a first!). The cosmic abundance of the different elements looks like this:

The Y axis is a logarithmic scale, so for instance hydrogen is about ten times as abundant as helium and even in terms of mass is more common than any other element except helium. One notable thing about this graph other than the clear rapid decline in abundance with atomic number (the X axis) is that it zig-zags because even-numbered elements are more frequently found than their odd-numbered neighbours. This is because many elements are formed by the collision of α particles, which consist of two protons and two neutrons. Phosphorus is flanked by Silicon and Sulphur on here, though it isn’t specifically marked, and its atomic number is fifteen, i.e. an odd number. Chlorine, which is quite common in living things because it’s part of salt, is less common still.

Elements are formed in various ways, and this relates to how common they are. The Big Bang led to the formation of mainly hydrogen and helium a few minutes later, as soon as the Universe was cool enough to allow their nuclei to hold together and their nucleons to form, although they would’ve been ionised for quite some time rather than being actual atoms. Small amounts of lithium and beryllium formed in the same way, and if the graph is anything to go by this looks like it might’ve been the main way beryllium in particular formed. Then the stars formed and the pressure inside them led to helium nuclei in particular being pushed together to form heavier elements. The crucial step in this phase is the formation of calcium when three helium nuclei collide. Then, a number of other things happen. The star may end up going supernova and scattering its heavier elements through the local galactic neighbourhood. It may also form new elements in the process of exploding through radiation. This was until fairly recently thought to be the main means heavier elements were formed, but another way has recently been discovered. When a star not quite massive enough to become a black hole collapses, it forms into what is effectively a giant atomic nucleus the size of a city known as a neutron star. When these collide, they kind of “splat” into lots of droplets. Neutrons are only stable within atomic nuclei. Outside them they last about a quarter of an hour before breaking down, and they often become protons in doing so. This means that many of the neutronium droplets form into heavier elements, which are then pushed away by an unimaginably powerful neutrino burst from the neutron stars and again scattered into the galactic neighbourhood. Two elements, beryllium and boron, are mainly formed by cosmic rays splitting heavier atoms. Some, particularly transition metals such as chromium and manganese, formed in white dwarf stars which then exploded, and technetium along with all the heaviest elements, have been generated by human activity.

At first, the abundance of phosphorus didn’t seem to be a big problem. However, after studying supernova remnants, scientists at Cardiff University seem to have found that there is a lot less produced in supernova than had been previously thought. This means that phosphorus is likely only to be as common as it is here in this solar system in star systems which formed near the right kind of supernova to generate it in relatively large amounts. Couple this with the essential function of phosphorus in DNA, RNA, membranes and ATP, particularly the last, and it seems to mean that at this point in the history of the Universe, life as is well-known on Earth is likely only to be found in initially localised areas, surrounded by vast tracts of lifeless space. The systems containing life would gradually separate and spread out through the Galaxy due to the migration of the stars as they orbit the centre of the Milky Way, but they would remain fairly sparse. However, as time goes by and the Universe ages, there will be more such supernovæ and phosphorus will slowly become more common, making our kind of life increasingly likely. If life always does depend on phosphorus, we may simply be unusually early in the history of the Universe, and in many æons time there will be much more life. This possible limitation may have another consequence. We may be living in a star system isolated from others which are higher than average in phosphorus, meaning that to exist as biological beings with a viable ecosystem around us elsewhere, we would either have to take enough phosphorus with us or make our own, and even the several light years between stars which we already find intimidating is dwarfed by the distances between phosphorus-rich systems in the Galaxy, which may once have been near us but no longer are, and not only do we have to schlep ourselves across the void, but also we have to take a massive load of phosphorus with us wherever we go.

But that is biological life as we know it. A couple of other thoughts occur. One is that there could conceivably be life as we don’t know it. This doesn’t work as well if the substitution of phosphorus is the main difference, because if that could happen, it presumably would’ve happened with us, and it didn’t, because other elements with similar functions would’ve worked better if they were more abundant and out-competed with the life which actually did arise unless there’s something about this planet which does something else like lock the possible other options away chemically or something. However, there could just be drastically different life, based perhaps on plasma instead of solid and liquid matter on planets and moons, which has no need for phosphorus or even chemistry, on nuclear reactions taking place between nucleons on the surface of a neutron star as suggested by Robert L Forward’s SF book ‘Dragon’s Egg’, or even nuclear pasta inside neutron stars. Maybe it isn’t that life is rare in the Universe, but that life as we know it is, partly because it needs to use phosphorus.

There is another possibility. We are these flimsy wet things crawling about a planet somewhere in the Galaxy, but we’ve also made machines. In our own history, we are the results of genes, and perhaps also mitochondria and flagella, concealing themselves inside cells and proceeding to build, through evolution, relatively vast multicellular machines to protect themselves. Maybe history is about to repeat itself and we are going to build our own successors, or perhaps symbionts, in the form of AI spacecraft which go out into the Universe and reproduce. Perhaps machine life is common in the Galaxy and we’re just the precursors. There is an obvious problem with this though, mentioned a long time ago: what’s to stop swarms of self-replicating interstellar probes from dismantling planets and moons and making trillions of copies of themselves? If this arises through a mutated bug in their software, it would be to their advantage, and they could be expected to be by far the most widespread “life” in the Universe. Yet this doesn’t seem to have happened. If it hasn’t, maybe the beings which built these machines never existed either. Or maybe they’re just more responsible than we are.

The Western Peninsula

The next post will be about Europa, so before I got to that I thought I’d mention Europe in connection with the idea of continents generally.

I would say there are six continents: Afrika, South and North America, Eurasia, Australia (Oceania) and Antarctica. Sometimes Afro-Eurasia and the Americas are considered single continents, and different countries disagree on how many there are. It’s the norm to separate Europe and Asia into two continents, but it’s also quite peculiar to do so for a couple of reasons.

The borders in the above map are the Caucasus and Ural mountains, and in fact the Urals in particular do mark a geological event. Laurasia collided with Kazakhstania in the Carboniferous Period. However, Europe has never existed as a separate landmass:

This is a world map of this planet in the late Carboniferous. The southern ice cap indicates that it was towards the end of that period. The continent crossing the Equator is Laurasia although it’s hardly recognisable as including Europe. The rest of Laurasia consists of Kalaalit Nunaat (Greenland) and North America. The Caucasus Mountains are the end of a chain stretching across Europe and interrupted by the Black Sea when Arabia collided with Eurasia as the Tethys closed in the Miocene. Hence the region we now call Europe used to be bounded by the Tethys and the Urals, but now has a land border. Even when it had a coastline along the Tethys, it was already part of Eurasia. North America and Eurasia began to part in the late Cretaceous and the process was complete by the start of the Eocene.

The Mediterranean islands are mainly considered part of Europe, but Cyprus is considered Asian. I presume this is because Cyprus is influenced by Turkey so strongly. In the Bronze Age, writing developed in Cyprus earlier than (the rest of) Europe, so Cyprus may tend to be less “backward” than Europe as a whole. However, at the time there seemed to be no concept of Europe and the hinterland of the Mediterranean was considered more important. Transport around the Med by boat was relatively easy due to its many islands and the proximity of the continental lands to each other. With the fluctuation in Saharan climate, the land would have been more hospitable and similar, although it takes longer than history to change.

As I mention tomorrow, one reason for the invention of Europe seems to have been to overcome the division between the eastern and western Roman Empires. I admit that I don’t understand how a name for an area of Thrace, almost in Asia, somehow ended up being applied to the whole of Europe. All that said, Europe is undoubtedly named after Europa, the wife of King Minos who was legendarily seduced/raped by Zeus in the form of a bull. Europa, as I will repeat tomorrow, means “broad face” but this may be a garbled etymology like our “sparrowgrass” for “asparagus” as her name might also be linked to Erebos, the personification of darkness, although how this happened is obscure. In fact I find the whole attribution of Europa’s name to Europe mysterious and contrived, even though it’s obviously named after her.

What of Asia? The Latin names “Africa” and “Asia” used to refer to provinces of the Roman Empire. Just in passing Africa Proconsularis was the former Carthage, conquered by the Romans, and comprised mainly a fairly thin strip of land in the area of present day Tunisia, Libya and Algeria. It was the second wealthiest province in the Empire after Italia, but the fact that it was a colonial power occupying part of Afrika seems to have been instrumental in the movement to spell the name of the continent with a K. I digress. There was Asia Minor, present day Turkey in Asia, and the lesser-known Asia Major, which seems to have been the rest of the known “continent” of Asia. Hence in a sense the words for all three “continents”, whereof Afrika alone is geologically real, are generalisations of relatively small areas in the Mediterranean region. The name Asia is lifted directly from the Greek  Ἀσία, which may be from the Semitic “‘asu”, meaning “rising” or “light”. If so, it literally meant “land of the rising Sun”.

“Eurasia” is naturally a combination of the two names, originating in mid to late nineteenth century CE Germany. However, there’s also the ethnic term “Eurasian”, denoting someone of mixed European and Asian origin and initially referring to Anglo-Indians at around the same time. This brings up the issue of how Commonwealth and American English differ in their usage of the ethnic term “Asian”. In North America, “Asian” refers to people whose heritage is East Asian, but in Britain it refers to south Asians. Both of these are technically speaking hyponyms for who Asians actually are, because for example many Arabs are Asians, as are people originating in Siberia and Israel, and none of these are “Asian” in either sense. The Y-chromosomal haplogroup world map of Homo sapiens looks like this:

A few things need to be said about this map. Focussing on Y chromosomes makes it a map of paternity, but there’s also mitochondrial DNA, which traces only the maternal line, and autosomal, i.e. the rest of the chromosomes, which are more mixed. It is, however, notable that Europe in this map is fairly homogenous, although the type most distinctive of Europe also turns up in the Middle East and Central Asia as well as Tchad for some reason.

The human mitochondrial DNA groups map looks like this:

It’s notable here that the area around the Mediterranean, including Arabia, forms a unit which includes the north coast of Afrika, but it then blends into other groups to the east. This makes Russia and Europe into a kind of genetic unit, but South, East and Central Asia are different. Hence in human terms, going by the maternal line there’s a gradient in the north between Europe and the Med on one side to eastern Siberia on the other, but sharper divisions in the south. In particular, the Indian subcontinent, which was a continent in its own right until it reached Eurasia in the Eocene, is very much a discrete unit in those terms, so the word “subcontinent” is most appropriate here. As far as Y chromosomes are concerned, north India is Aryan and south India Dravidian, which is supported phenotypically and linguistically. Other chromosomes are of course available.

All that is of course fairly anthropocentric. There are also zoögeographical regions and geobotanic realms. An early map using this idea looks like this:

This seems pretty close to how it’s seen today, although I’ve also heard of a “Holarctic Region” which combines North America and Eurasia. Actual Arctic fauna are pretty much unified around the Arctic Ocean and there are the likes of bears, bison, wolves and so forth in both Eurasia and North America. From this perspective, either all of the land clustering around the North Pole plus the north of the Sahara constitutes one region or Eurasia and North Afrika do, except for India and Indochina. Individual species of animal are often referred to as “Eurasian”, such as the Eurasian beaver or Eurasian sparrowhawk. There are many of these. To some extent the fauna of the whole of north Eurasia and north Afrika can be expected to be quite similar, although many species will have smaller ranges within that and there is also migration between regions. This map also reflects the mitochondrial DNA distribution of our own species.

By Dietzel – Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1703126

Floristic regions look like this, although it’s possible to be a lot more detailed. It’s notable that the flora of Southern Afrika, actually southern South Africa, is as distinctive as other much larger regions, and the most distinctive human population genetically is the San of southern Afrika, who can be as distantly related to each other as randomly selected members of our species outside that group and may have been separate for as long as our species has existed, with some interbreeding of course. Once again, looking at the rest of the land surface of the planet, there’s a Holarctic Region.

As I must’ve said before on this blog, I often think of the Americas not as the West but as the extreme far East, because the Bering Straits and the Pacific coast of the continents link them to the Pacific and East Asian regions. The connections between the two are evident in these maps. If we’re going to think of the planet in these terms, there’s a tendency for the North to be united and the South to be more disparate, and that makes sense, for example, closer to the Equator where a cylindrical projection can be misleading because it makes locations in the tropical belt look closer than they really are compared to the polar regions. There also seem to be physical barriers in the South such as oceans, and in the southern part of the Northern Hemisphere in the form of the narrow isthmus of Central America, the Sahara and the various mountain ranges of Asia. I notice here that I’m still calling it Asia. In all of these respects, although there are fairly sharp divisions within Eurasia, and within Afro-Eurasia, they don’t follow the actual boundaries between the alleged continents closely at all. Just as in the Greco-Roman world, the Med seems to be a more important region than Europe and the most significant “borders” are actually in central and southern Asia. That said, just as we recognise a difference between North and South America because of the narrow link between the two continents, we should likewise recogise that the Sinai region represents a border between Eurasia and Afrika. Arabia is a little ambiguous in this schema though. It’s also notable, incidentally, that both of these regions have significant canals, which would be unnecessary to trade and shipping had the Tethys still existed. Separation between continents seems to be marked by bottlenecks of land. There is of course no such bottleneck between Europe and Asia. Hence Eurasia.

By Monsieur Fou – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=21997237

All that said, the idea of Eurasia can be used negatively. The Eurasian Economic Union comprises the former Soviet states and has similarities with the European Union. It seems to build on an older idea of Russia as a Eurasian territory rather than a European one. The Eurasia Movement is another Russian idea which opposes American liberalism and capitalism but mixes it with the values of the Russian Orthodox Church. Whatever its values, Eurasianism reflects the apparent reality that Russia occupies the greater part of the Eurasian continent and the Urals are in a sense merely a mountain range within that country. It makes the concept of Russia less Slavic. Neo-Eurasianism sees the country as more Asian than European, which is geometrically true, and to some extent the above also corresponds to the scientifically-established divisions seen in the other maps on this post. However, sociology is usually flawed when it considers itself akin to the natural sciences, and this is actually divisive compared to a more cosmopolitan version of the concept of Eurasia.

My general aim in discussing this issue is to undermine the “specialness” of Europe. Although Europe can be seen as a bastion of liberal democracy, and to be honest the idea of living in most of the rest of Eurasia is quite forbidding to me, it can also be seen as a kind of White fortress hoarding the wealth and resources plundered from the rest of the planet. That said, I thoroughly consider myself as Northwestern European and I have to say that my perception of much of the rest of the continent is as illiberal, sexist, homophobic and so forth, and I would be afraid to live far outside my hexagon, so I suppose I’m just a creature of my own geography. Nonetheless, I think it makes sense not to regard Europe as a continent at all, because if we don’t, we may become more concerned with those very illiberal and anti-progressive tendencies which are going on in the rest of the continent or Eurasia.

Hence I’m going to stick with my initial urge and say that there is no continent of Europe. There is a vast continent called Eurasia. To its west is an unusually large peninsula and a number of archpelagoes and more isolated islands, and there’s the Mediterranean, around which similar lands cluster. We blend ethnically into people to the south and east, unlike many other people on the continent who are much more discrete than we are. But at the same time we need to be wary of the idea of a Eurasian identity being used for imperialist ends. Nonetheless, we live on a peninsula called Europe, or rather on one of its islands in our case, and that peninsula is part of Eurasia.

Two Pieces Of Evidence For Evolution, And The Nature of the Bible

This post tries to do the same for evolution as this did for the Earth being a globe, but with an additional bit on the nature of sacred texts in general, focussing on the Bible. It isn’t supposed to be a thoroughgoing survey of evidence for evolution so much as just a couple of tests which can be done fairly easily which demonstrate that it’s fantastically improbable that evolution didn’t happen. I’m also going to mention a couple of other things supporting evolution. This is A-level biology stuff. It isn’t so sophisticated as to be hard to understand for a lay person. I’m also repeating myself here but it’s worth it for the sake of a more targetted post.

Immunological Studies

I should point out first of all that there is a major ethical issue with this one, and possibly also with the other one depending on the organisms on which it’s carried out. Most vertebrates have an immune response somewhat similar to memory. When we’re exposed to certain substances, our bodies come to recognise them and deploy defences against them. This is often more harmful than helpful, but the way it’s done is for the immune system to manufacture large molecules called antibodies whose surfaces match the molecular structure of the surfaces of the molecules they neutralise, like jigsaw pieces fitting together. They also match other molecules with sufficiently similar shapes. There’s an example of this in vaccination. The BCG vaccine, used against tuberculosis bacteria, also works against the leprosy pathogen because the two are closely related and have similar compounds on their surfaces. Both are in the genus Mycobacterium and are about as closely related as horses and donkeys.

In fact you can even use horses and donkeys to demonstrate this. If you take a blood sample from a horse and inoculate a rabbit with it, not only have you done something extremely unethical but you’ve also caused the rabbit’s immune response to recognise a particular set of molecular patterns as found in the blood of a horse. If you then take a blood sample from the rabbit and combine it with the blood of a donkey or zebra, it will similarly show an immune response but not as strong as it would to a horse. It would show a weaker response to the blood of a tapir or rhino and a much weaker response to a more distantly related animal such as a human. Incidentally, you could do this with any set of mammals. The rabbit is not crucial here. Inoculating a human with horse blood in the same way would produce an immune response which would be steadily weaker with more distantly related animals.

This happens because the proteins found in animals tend to vary in detail from species to species, but these variations are usually not directly related to their function, which means that random mutations in their DNA often result in different amino acids in the chains. I should probably explain this a bit better.

DNA codes for proteins. That’s what genes are: instructions for building proteins from amino acids. Amino acids have small molecules with groups at either end which can bond to each other quite easily. These form chains known as polypeptides. Some amino acids can also bond at their sides using sulphur atoms, which enable the chains to fold into particular shapes. If one of these changes, it’s unlikely to preserve the function of the protein, but it often doesn’t matter much what the chain of amino acids other than the ones which link is made of in detail. Consequently there is no pressure for them to conform, and organisms simply will tend to become more chemically different from each other if they don’t form part of a single breeding population. This means that these immune responses are effectively using an animal’s immune system to measure how closely related to each other two organisms are, and the variations are not normally anything to do with how the organisms have been “designed”. They’re simply random differences.

DNA Strand Bonding And Temperature

This can be carried out more ethically than the immune system, although it’s practiced differently. This one basically looks at the code for making the proteins rather than the proteins themselves, but has the advantage of including an organism’s entire genome rather than just the proteins produced by its genes. Most DNA is non-coding. Actually, you know what? I’m going to introduce the nature of DNA here.

DNA is the molecule which stores genetic information in most organisms. The exceptions are certain viruses which use RNA instead. DNA is arranged like a ladder, with the sides consisting of a sugar called deoxyribose and a phosphate group. These are linked to the half-rungs, consisting of four compounds, two with a pair of rings and two with single rings. These are cytosine, guanine, thymine and adenine, known as bases. Each can only bond with one of the others, cytosine with guanine and adenine with thymine. The whole assemblage twists in a double helix like a spiral staircase. On a larger scale, the DNA molecule coils again like a telephone handset cable, and several times again, packing the whole molecule into a small space. There are also globules of protein which help it stay in this arrangement. On a higher level the molecules are organised into two larger systems visible under a light microscope. These are chromosomes and plasmids. Plasmids are loops of DNA not found in the nuclei of cells but found in the likes of bacteria, mitochondria and chloroplasts. Chromosomes are usually paired in most organisms, or at least animals, but they can also either be single or in groups of several such as threes or sixes. Humans usually have forty-six chromosomes. Most of the time they’re invisible because they’re packed away but sometimes there are giant chromosomes, as in the salivary glands of fruit flies, and they become discernible when cells divide.

DNA encodes genes in the “rungs”. Every amino acid has a three-base code, or several codes, and there is also a “stop” codon which ends protein transcription. Every gene codes for a protein, but further down the line these proteins are responsible for the manufacture of other chemicals and structures, or for their acquisition and movement from the external environment, so living things are not just made of protein.

Most DNA is non-coding. That isn’t the same as non-functional. For instance, the centromere some way through the chromosome has a certain pattern of bases which makes it easier for the spindles to pull on the chromosome during cell division and the telomeres at the ends of the chromosomes stop the genes towards those ends becoming deleted or damaged when cells divide. Much of it has no clear function, which is of course not the same as it having no actual function. In a way, non-coding DNA is like dark matter is supposed to be, in that it constitutes the majority of the genome but is “invisible” in that it doesn’t turn into proteins. This means that whereas it could constitute the design of an organism if you’re going to go all teleological on us, it probably doesn’t. It could be anything most of the time. Something like 99% of the human genome is thought to be non-coding. Some other organisms have much more coding DNA than humans. For instance, there’s a species of seaweed with only three percent.

Protein transcription occurs when the strand is unravelled by a protein (the purple blob in this clip, which shows replication rather than transcription). It’s possible to use these enzymes to separate DNA into single strands. If you did this with a human sample and put it into solution, the corresponding bases in the DNA would tend to align and recombine. If that solution were then heated sufficiently, it would separate again. However, if single-stranded DNA samples were to be made from a chimpanzee and a human, they would combine to a certain extent but maybe about one percent of them would not bond, and when heated in solution will separate at a lower temperature. This trend continues with increasingly distant relatives, such as humans and cats, humans and kangaroos, humans (let’s just stick with ourselves for now) and cobras, humans and fruit flies, humans and bananas and so on. Each of these will separate at lower temperatures than its predecessor. This is because they have fewer and fewer bases in common.

Now, it’s possible to imagine that organisms that occupy similar ecological niches will be genetically similarly “designed”, so you might expect, for example, that an aardvark and an anteater would, if designed, have a lot of genes in common, such as genes for a long snout, powerful claws and digestive enzymes for breaking down insect cuticles. This would make sense if the animals in question were designed. However, studies such as this and the immunological technique mentioned before show that aardvarks are not closely related to any other mammals although they are somewhat related to manatees and elephants, that is, that they have more DNA and genes in common with them than anteaters. By contrast, anteaters can be shown by the same methods to be quite closely related to armadillos and sloths, and as a group these three clades are only very distantly related to all other mammals. It has nothing to do with design. The non-coding DNA underlines this as there is no reason for it to be faithfully copied if it has no function. All it does is indicate how closely related organisms are.

My own genome shows that I am mainly Scottish and Irish (i.e. I’m ethnically a Gael) with some apparently Mestiço ancestry originating in West Afrika or the nearby islands. This corresponds with what I know about my family history and health and isn’t even slightly surprising. Established genome sequencing techniques confirm what I already knew or strongly suspected. It’s just a way of tracing family history, among other things, and it works beyond our own species to establish common ancestry all the way back to LUCA – the Last Universal Common Ancestor, thought to have lived somewhere between 3 480 and 4 280 million years ago. I imagine it wouldn’t work on viruses to link them to other organisms usefully, as they might have RNA genomes or genes which have been transcribed into the genomes of hosts. But there is no qualitative difference between me discovering I have West Afrikan relatives and a scientist discovering armadillos and pangolins are not closely related but armadillos and anteaters are.

A Couple Of Miscellaneous Points

There used to be a sea urchin whose madreporite (the orifice urchins and their relatives use to ferry sea water in and out of their bodies) started off in the centre of its shell and it gradually moved towards the edge. There are plentiful fossils of this sea urchin in chalk cliffs, and the further up you climb from the beach in, say, Dover, the closer the madreporites on these fossils are towards their edges. This is clear visual evidence for evolution, although it uses fossils, which leads some people to doubt. Therefore here’s another. Mammals have a nerve supplying their larynxes called the recurrent laryngeal nerve. This travels down the neck, loops round the collar bone and then comes up towards the larynx. In most mammals this is fine and a slightly odd but functional arrangement. It’s also true of giraffes with their almost two metre long necks. They have a nerve whose only function is to move the larynx which is three and a half metres long, when it need only be well under a metre in length. This may actually be one reason giraffes are so quiet. They can make a low grunting noise and that’s it. This may or may not be useful. One thing which is clear, though, is that this is not a sensible way to design an animal. The only reason giraffes’ recurrent laryngeal nerves are this way is that they’re descended from okapi-like animals with much shorter necks. I find this to be one of the best pieces of easily stated evidence available to support evolution.

The Bible

This came up twice recently, once in connection with flat Earthers and once with young Earth creationists. It’s notable that historically, young Earth creationists have tended not to believe Earth is flat, although more recently more of them seem to. Before that, for a long period there was only a tiny minority of Christians who were flat Earthers, although more seemed to have a problem with evolution. To an extent it’s a waste of time to engage with them, for a couple of reasons. One is that there are more pressing concerns in most people’s lives, and another is that they don’t seem to be willing to listen. It’s also very difficult to determine if they’re in earnest, but there are people who spend a lot of money and resources into promoting the idea that Earth is flat, suggesting that they really do believe that.

The Bible, and here I’m including both the Tanakh and the New Testament as I get the impression that Christians proportionately outweigh faithful Jews among flat Earthers, is a collection of disparate texts. If you are a faithful follower of either or both parts, the chances are that the main reason you take it seriously is that you regard it as a guide to living righteously. Because it’s so varied, it can’t be categorically said that none of it is a science textbook, particularly Torah. Torah has what appear to some to be instructions on hygiene, for instance with respect to infectious diseases, and dietary prohibitions which it’s often been argued are linked to avoiding parasites. That may or may not be what they’re about. Jewish traditions often seem to involve disputations about the true import of a text and as a Goy I probably shouldn’t comment. I am, however, aware that that view exists, and consequently it isn’t entirely true to say that the Tanakh is never supposed to be taken to refer to something like science, accurately or otherwise. All that said, the chances are that such a wide-ranging and enormous corpus as the Tanakh and the New Testament would end up revealing something about the human writers’ views on the nature of the physical Universe. Jewish cosmology seems to look something like this:

By Tom-L – Own work Based on File:Early Hebrew Conception of the Universe.png and several other depictions, including Understanding the Bible, Stephen L. Harris, 2003., CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=99817773

That’s all entirely clear, or rather can be gleaned from various parts of the text. The New Testament view seems to be somewhat different, as from Paul’s comments about the Seventh Heaven it seems to have incorporated the Greek view of a cosmos consisting of nested spheres, each bearing a planet or the fixed stars. At that time, the Jews were largely Hellenised, some of the authors, such as Luke, were well-educated and it seems that such ideas as those of Eratosthenes and Aristarchus had filtered through. However, the gospels refer to Satan taking Jesus to a high place where all the nations of the world could be seen, and the risen Jesus ascends into Heaven, which strongly suggests a “sandwich”-type cosmology of a flat Earth and heaven. Even Luke mentions these, and they seem to imply Earth’s flatness. However, what’s more important about the incidents? What do they communicate? Surely that Satan tempted Jesus with great Earthly power in return for submission to him, which Jesus rejected, isn’t it? The Ascension is harder to account for, and to me at least the suggestion that it’s an “acted parable” is not convincing. Even so, the idea communicated is that Jesus Christ is God. Focussing on Earth’s shape because scientifically ignorant people, which basically everyone was at the time anyway by the way, is utterly beside the point.

This can be seen elsewhere in the Bible. For instance, there’s a passage which refers to plants forming a barrier which have either stings or thorns. The details are not important. Torah refers to insects using a word translatable as “quadruped”, as it contains the Hebrew term for “four”. I’ve seen Christians attempt to argue that it refers to locusts because their hind legs are for hopping and don’t count as legs, which I find silly and pointless.

Conclusion

Not only is it unnecessary to be creationist or a flat Earther to be a faithful member of the Christian or Jewish faith, but in the case of the former it’s actually questionable to be due to the fact that unlike Judaism, Christianity is an evangelising faith, and to insist on creationism or belief in a flat Earth is both a barrier to evangelism and a refusal to use the divine gift of reason. Anti-theists would possibly be very happy with Christian flat Earthers because they give Christianity such a bad image. However, it just isn’t necessary to believe either absurdity to be Christian.

. . . Not As We Know It . . . Captain

If your first language is English and you’re over about thirty-six, I’m guessing, you may well remember this song. If you’re a bit older you’ll also remember their song about Arthur Daley, and you’ll also know who that was. I only realised recently that there was a claymation video for it though, because in 1987 CE I wasn’t watching television, with the exception of the repeat of ‘The Hitch-Hikers’ Guide To The Galaxy’.

One of the oft-repeated lines, alleged to be a quote from the original series, was Spock saying “Well, it’s life Jim, but not as we know it. . . Captain”, with a distinctive pause at the end of the verse before the Spock impersonator says the final word. It won’t surprise you to know that just as Kirk or anyone else never said “beam me up, Scotty”, this is a misquotation. The closest Spock comes to saying it is “no life as we know it” in ‘Devil In The Dark‘, when in fact he says it twice, and that episode in particular refers to a very common suggestion regarding “life, Jim, but not as we know it” – silicon-based life.

I have already discussed this here:

Without re-watching the video, my conclusion was that there are two ways in which life which could be said to be silicon-based are possible. Because silicon compounds are often bioactive, and silicon-based structures do exist in organisms on this planet, a situation could arise where much of an organism’s biochemistry involves silicon compounds, even including hormones and much of the hard parts of their body, but at core still carbon-based. The alternative is that a narrower range of silicon compounds which are however particularly versatile could be used in a manner similar to the difference between binary and higher-based ways of representing numbers. It can still be done, but the binary representation of the number eleven takes four bits but only one duodecimal digit. Hence silicon-based life could still exist but be more “long-winded” than carbon-based, and consist of relatively larger molecules than the already very large macromolecules found in terrestrial life such as muscle protein and cellulose. However, although I think it’s likely to be possible, I don’t think it would emerge of its own accord or be able to survive outside a specially designed environment, mainly because silicates are very stable compounds and once silicon has entered such a state it would be difficult to remove it. If you watch an exposed microchip under a microscope, you can see it visibly degrading and not-so-gradually oxidising. An environment containing silicon-based life of this kind would have to be free of oxygen and water. Silicon in water liberates hydrogen and combines with oxygen to become silica, and this may not happen with the silicon compounds used for life, but there’s a risk of producing bonds which are so strong that ordinary biochemistry can’t sever them all the way through silicon-based biochemical pathways.

Only the lightest atoms are able to produce more than single bonds. This includes boron, carbon, nitrogen and oxygen. As far as I know, no heavier element is able to form more than single covalent bonds. This means that the structures of molecules made up of chains or rings of silicon atoms may be rather limited, although silenes do contain double silicon bonds. Moreover, the stability of longer chains of silicon atoms is lower than that of carbon chains with the same number of atoms in them. Nonetheless, I do believe silicon-based biochemistry is possible and I will now cover some of the possibilities.

By Zephyris – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15027555

DNA is a well-known helical polymer used to store genetic information. Silicates have various forms, consisting of sheets of hexagonally-arranged silica tetrahedra sharing vertices, alternating such tetrahedra with opposite orientations, simple chains of the same, or helically-arranged such chains. This is interestingly close to DNA, although it’s only a single helix and the unit is silica groups. There are also double chains known as amphiboles, linked via shared oxygen atoms. Some asbestos minerals are amphiboles. If these are able to form extra bonds with bivalent atoms of various kinds, the result would be a very similar molecule to DNA, with a potentially readable code, although how it would come uncoupled, be transcribed, what it would be transcribed into, and how it could replicate and recouple are different questions, which may not have answers. Nevertheless, this is a potential storage medium, perhaps one which would need to have more “steps” than DNA per codon. This illustrates what I mean by molecules needing to be relatively larger, although on the other hand the actual rungs are smaller because they only consist of two atoms.

Closer analogues with organic compounds are the silanes and silanols. The former are silicon-based versions of the alkanes such as methane, butane and propane. Like them, silanes are flammable, and become more flammable the longer their chains are because longer chains are less stable. In the case of alkanes, similar substances can be derived from them in the form of long-chain fatty acids, with a -COOH group on one end. These are just ordinary organic acids which happen to have very long chains, and in organisms they’re often joined together by a glycerol residue at one end into kind of E-shaped molecules, used to store energy and form cell membranes. Eicosapentanoic acid is quite a well-known essential fatty acid. It has mixed double and single bonds, like all polyunsaturated fatty acids, and twenty carbons per molecule. By contrast, the highest silane has only six carbons, and is entirely saturated because they only have single bonds.

Silanols are the silicon-based versions of alcohols, although many of them are in fact organosilicon compounds rather than containing no carbon. They’re more acidic than their organic equivalents and can be used in shampoos to improve the pH balance of the scalp and hair. Another class of silicone compounds in common use is the cyclosiloxanes, which are hormonally active, found in cosmetics and toiletries and are persistent in the environment. As far as this particular biosphere is concerned, these substances are concerning, but their bioactivity suggests that in other circumstances they could be functional as biochemicals. Many of these contain oxygen bonds, which may be why they aren’t broken down. It may not be that they are merely difficult to process in organic biochemistry, but just difficult to do so in any circumstances conducive to chemically-based life, and if that’s so, the chances are that compounds with silicon-oxygen bonds may break down in other ways but not in such a way as to become usable again by living systems. This would ultimately result in a silicon-based biosphere having all its silicon locked up with oxygen, which is how things are here.

It would be interesting to attempt to replicate the Miller-Urey experiment with silane instead of methane. This was an attempt to replicate the chemical conditions of Earth soon after formation to discover whether biochemicals found in life today would form, and it succeeded. It used water, ammonia, methane and hydrogen, and resulted in the production of such compounds as the amino acid glycine and the sugar ribose. However, although this is a fruitful exercise, it doesn’t reflect the kind of conditions likely to exist in any real situation. The interstellar medium does contain silane and several other silicon compounds, so this is not entirely unrealistic, but the concentration of silane and other silicon-based substances is much lower than their carbon-based equivalents.

A strong argument against silicon-based life could be made on the basis of the existence of organic life on this planet. Silicon is almost a thousand times more abundant that carbon, and yet life developed based on this far less widespread element. This might, though, result from other conditions being unsuitable such as the presence of water, which is however the most abundant compound in the Universe. For silicon to combine with ease in other ways, oxygen would have to be relatively scarce. On Earth, oxygen is the most abundant element in the crust, much of it combined with silicon, and I may be wrong but I find it hard to imagine a rocky planet whose situation is different enough to enable silicon to form other compounds routinely. Oxygen is the third most abundant element in the Universe as a whole, and is more than a dozen times as common as silicon. It isn’t necessarily that silicon-based life is impossible so much that other factors make it unlikely ever to happen on its own, without intervention.

That said, there might be a reason for manufacturing silicon-based microbes, for example, to reclaim plastic waste or as part of a manufacturing process. In a sense, microbes are highly complex nanotech devices, and organic life forms can only do so much because the range of conditions in which they can function is limited. The same applies to silicon-based life, but this is a potential advantage as it prevents the “grey goo scenario” of self-replicating devices eating up the planet. This brings up the issue of exotic solvents.

Although silicon biochemistry is bound to be very different to its carbon-based equivalent, what I’ve described so far is substantially similar, and as such it would require a solvent. It can’t use water unless silicon enzymes are able to catalyse in those conditions without being damaged. Silicon-based life attempting to use water is like carbon-based life attempting to use mercury as a substitute for water, which would combine with the sulphur in proteins and destroy their structure, except more severely because any silicon atom with free electrons would bind to the oxygen, liberating hydrogen incidentally, but also knackering the structure of its macromolecules. This is the big problem with silicon-based life in fact, and although I’ve suggested that entirely artificial silicon-based life forms could be used to clean up the environment, they would have to be exposed to water to do their job, which would be very harmful to them. Although glass, silica and many other silicon compounds are excellent at keeping water out without reacting, some kind of solvent would need to get in there with the molecular machinery that’s actually doing the living, i.e. the metabolism, if the biochemistry has any similarity to that of life as we know it.

One possibility here is methanol. This is the simplest alcohol, with this structure:

Somewhat ironically, the reason why this might work is probably that it has a carbon atom bound to the oxygen, which is stronger than a silicon-oxygen bond, so silicon will not pull it away from the molecule and annihilate its own structures. Methanol is found in the interstellar medium, and there’s no reason why it wouldn’t occur on planets. Its melting point is -97°C, so in an atmosphere it’s entirely possible that liquid methanol could exist on the surface of a planet, though above the melting point of water ice it would do so as a mixture with water, which would be unsuitable, so if there are worlds with methanol oceans that might be a start. However, methanol is not as abundant as water, unlike another candidate solvent, sulphuric acid. Sulphuric acid is widely distributed in our own solar system, on Venus, Mars and Io for example, and this suggests that there are whole planets out there with sulphuric acid oceans, or at least lakes. Sulphuric acid seems to be much better at supporting diverse silicon chemistry than water is.

It isn’t entirely true that silicon never forms double bonds. This occurs in silene, for example. I have to be honest here and confess that I don’t know if the existence of a double bond in silene means it can occur in any other situations. While bonds are under consideration, it’s worth looking a bit more closely at the differences between carbon and silicon chemistry. The covalent radius of a silicon atom is 117 picometres compared to carbon’s 77, but the length of the silicon-oxygen bond is 163 pm compared to carbon’s 143, from which the radii must be subtracted, leading to a shorter bond length outside the covalent radius for silicon, which makes the molecules more potentially crowded for the latter and so less diverse. There just isn’t the space around silicon atoms for there to be as much variety per atom.

That said, one thing I haven’t considered yet is the question of siloxanes. Is it possible that rather than envisaging an oxygen-free environment for silicon-based life, we should be thinking in terms of just letting it happen and seeing where that would lead us? Siloxanes include both cyclical compounds and silicon oils and rubbers, all of which have their parallels in carbon-based biochemistry. Silanols are siloxanes in a sense because they have the silicon-oxygen bond, and it’s possible to build other compounds from them. Oxidation leads to the formation of silica, so this may ultimately be an unstable situation for life to exist in, but perhaps for a short period it could.

Life as we don’t quite know it, that is, still relying on complex chemistry and solvents, has certain requirements. By definition, it needs a solvent, which in our case is water but could hypothetically be various other compounds including the aforementioned sulphuric acid and methanol, but also potentially formaldehyde, ammonia or hydrogen sulphide, which I’ll talk about in a bit. It needs enough different kinds of chemicals to perform various functions, and it needs the right balance between chemical stability and reactivity. It can’t afford to have a “doomsday pathway” where an essential and irreplaceable function causes a reaction to practically inert compounds, because this would end up locking all of the central elements up in those substances, and this appears to be what silica is in the case of silicon-based life. On the other hand, this could be useful in biotechnology to protect the environment, as it amounts to artificial organisms cleaning themselves up after their work is done.

Hence I would say that silicon-based life of this kind is possible if it was carefully designed and functioned in a highly specialised and protected environment, but it could never kick-start itself. It’s feasible that a sealed vessel in a lab could be provided with an appropriate solvent, be free of water and oxygen and be seeded with a variety of silicon-based chemicals by an intelligent life form or machine intelligence and then either spontaneously assemble into simple life forms or be purposefully manufactured as such, and there are also reasons for doing this, but there is very probably no world anywhere in the Universe where this happened on its own. In fact, if we did happen to find a planet or moon with silicon-based life on it, it would be good evidence for the existence of intelligent life somewhere.

Having said all that, there are other ways in which life could be silicon-based than simply imagining the mimicry of organic biochemistry, and perhaps all these stringent requirements just mean that biochemistry as such only really applies to our own very specific kind of life. Nowadays, classical computers are silicon-based, with doping from other elements, e.g. traces of arsenic to alter the atomic structure and allow them to function as arrays of transistors. However, this requires conditions where elemental silicon can form or be deposited, which are hard to imagine. It’s also interesting from the perspective of whether intelligence has to be alive. It’s possible to imagine some kind of crystalline process occurring on a planet where transistors or other switches grow out of inorganic materials which never fit the criteria of life but nevertheless evolve and increase their information processing capacity until they count as intelligent. This, however, is evolution and that would arguably make something alive. For instance, it would reproduce. A much more straightforward way in which intelligent machines could appear would be through what we’re doing now with our development of artificial intelligence, and many have claimed that a solution to the Fermi Paradox, for instance, is that interstellar intelligence is entirely machine-based. Considering the current trends in AI, space travel, nanotech and genetic engineering, a combination of applications of these in the long term could lead to self-replicating intelligent spacecraft who would be very much at home in interplanetary space if not interstellar, the problem there being energy sources, which could be addressed by going into a sleep mode and coasting, perhaps for centuries, to reach resources, which is far more practical for a machine designed to do that than a human, although for all we know other intelligent life forms might be absolutely fine with dormancy over long periods due to the conditions they evolved to cope with. Such entities probably wouldn’t consist of biological materials as we understand them and the usual restrictions on biochemistry assumed above wouldn’t apply. No solvent would be needed, a few inorganic compounds and elements would be sufficient and so forth.

Returning to “life as we know it” to some extent, there are several possible biochemical options which have not been mentioned yet. Prominent among these is boron. Like carbon and silicon, boron avidly forms covalent compounds though with three bonds rather than four. It forms three covalent bonds and is a metalloid, with some properties typical of metals and some of non-metals. The compounds it forms are often based on polyhedral forms, either closed or like a basket, in which atoms of other elements can be incorporated. It has at least eight different pure forms (allotropes), similar to carbon’s diamond, graphite, fullerenes and bucktubes. On a molecular level it tends to form icosahedra and there is a fullerene-like form consisting of forty atoms. It also has an extensive chemistry with an affinity for ammonia.

Hence boron chemistry can go in two directions towards complex structures with behaviour. On the one hand, it can be like conventional biochemistry, but with ammonia rather than water as a solvent, so it can have complex carbon-like chemistry. This might involve boranes, which are explosive in oxidising environments such as our own lower atmosphere but would be more stable in a reducing atmosphere, such as one mainly consisting of hydrogen. Boranes are boron hydrides, but differ in shape from hydrocarbons because they tend to form the basket shapes mentioned already, or icosahedra. It can form double bonds like carbon. Hence it’s possible to imagine boron-based life living in a hydrogen-rich atmosphere in conditions where ammonia is liquid and acting as a solvent, on a relatively cold world whose temperature is around -77°C or above, how high exactly depending on the atmospheric pressure. Such conditions are possible on the super-Earth/sub-Neptune planets which are in fact the most common of all types of planet but are not found in this Solar System, which is a puzzle, provided they are just outside the “Goldilocks Zone” for our kind of life.

On the other, there’s the possibility, which also exists for carbon, of nano-“machines” being built from the structures which pure boron forms. Hence there is perhaps another route into life which is not really biochemical. The interesting thing about boron, and it can be interesting in spite of its name, is that it kind of straddles biochemistry and nanotech in a way carbon doesn’t. With carbon, the structures of biochemistry are of course exceedingly useful and versatile, but they generally consist of polymers. Boron is able to form molecules with unusual structures which are kind of quasi-crystalline and can work both mechanically and chemically.

There is, however, a big issue with boron I haven’t mentioned yet. It’s rare. It’s less common than the next fifteen elements, up to scandium, and also the second rarest of the four lightest elements, beryllium being much more scarce due to the difficulty of its formation. Hence, whereas boron has exciting possibilities as a basis for life, like silicon it’s unlikely ever to happen without intervention. If anything, it’s more likely even than silicon to act as the basis for biochemistry, but silicon is the seventh most abundant element and boron the thirty-fourth. It’s possible that shortcomings in silicon chemistry prevent silicon-based life, but in the case of boron it could merely be its scarcity compared to carbon.

This probably exhausts the possibilities of elements as the basis for life using similar biochemistry to our own, but it doesn’t have much relevance to other possibilities for life. I’ve already mentioned plasma-based life, to which chemistry isn’t very relevant and it is possible that we’ve got a bit too hung up on chemistry as the only possibility. Another couple are associated with neutron stars. Firstly, there is the option explored by Robert L. Forward in his ‘Dragon’s Egg’ novels. Forward imagines that neutrons on the surface of such a star could combine in various ways like atoms do into molecules, and have their own equivalent to chemistry. They would however have lives millions of times faster than ours, and he also supposed that their life expectancy would be around half an hour, which is quite reasonable. There is a second suggestion concerning the interior of a neutron star which was explored by Stephen Baxter in his Xeelee series, which I haven’t read and don’t understand, and there is also the Orion’s Arm version, which may be related, of Hildemar’s Knots. These are quite difficult to understand and explain, but seem to depend on the probable fact that the interior of a neutron star is likely to be superfluid and have quantised microvortices of rotation. In order to explain this, helium II is a little closer to everyday experience.

Helium is the only baryonic matter with no solid state under pressures encountered routinely on the surface of this planet. This is a little abstract as it also has the lowest boiling point of any substance, and therefore can’t be stably surrounded by a gas under pressure since everything else is solid at that temperature. There are two common isotopes of helium, helium-4 and helium-3, and because of the way spin works, one consists of bosons and the other of fermions. Above a certain temperature, all helium behaves rather like an ordinary liquid except for being almost invisible, but below it, the helium-4 isotope becomes what’s referred to a little confusingly as helium II. At a much colder temperature, helium-3 also enters this state, which is referred to as superfluidity, and is a macroscopic quantum state. It behaves as a mixture of ordinary fluid and a fluid with no viscosity at all. It can climb vertical surfaces and it flows more easily through small holes than large ones. It conducts heat at the speed of sound, a feature also found in superconductors which means that effectively a small amount of helium II is always at the same temperature throughout. With respect to Hildermar’s Knots, the important property of superfluids is that when they’re stirred, they continue to rotate forever because they have no viscosity, and the vortex formed is quantised, and due to the peculiar nature of half-integral spin things then become really confusing. Neutron stars spin very fast and this, I think, stirs the interior superfluid neutronium into quantised vortices, each exhibiting a single quantum of angular momentum and also of magnetic flux. This results in a dense tangle of filaments. Something called the Urca Process involved in the cooling of neutron stars leads to an excess of left-handed electrons which become spin currents. The topology of these filaments changes if they touch, leading to a wave being emitted through the medium. Braids of these filaments amount to life because they can consume left-handed electrons, the braids can store information and the waves propagate signals like nerve impulses. In Orion’s Arm, Hildemar’s Knots can’t relate to the Universe outside their neutron star and regard it as an abstract mathematical problem rather than the Universe. Likewise, attempting to get one’s head round what quantised vortex filament braids in neutronium within neutron stars actually are is very like trying to solve an abstract mathematical problem. It isn’t clear to me how much of this is handwaving, but if it isn’t, it’s an interesting observation because it means that both modes of life regard the other as arcane and abstract. Also, neither can approach or exist in the other’s realm. This goes beyond “environment” because the interior of a neutron star and the kind of space compatible with atomic matter are so different that they hardly make sense to each other. Although a neutron star is only the size of a medium-sized city considered from the outside, they will distort space to some extent on the inside, and the amount of matter within them is enough to make half a million Earth-sized planets. Moreover, all of this would be happening on an absolutely minute scale.

There’s a second kind of theoretical filamentous life which may exist within less extreme stars, made of cosmic strings. Before I launch into this, I want to point out that I have my doubts about the very basis of this life form. There is an issue with magnetic monopoles, and it goes like this. We’re used to the idea of positive and negative electrical charges and the idea that one can exist without the other. There are positrons, protons, electrons and muons, all of which have isolated charges which are not paired by their opposites, although they attract each other. It might be thought that south and north magnetic poles could also exist alone, but this has never been found, and if a bar magnet is cut in half sideways it just becomes two smaller bar magnets with a north and south pole each. This seems to go on no matter how many times it’s done. Remarkably, this was discovered in the twelfth Christian century and the reason for it has never been discovered. Physics as it stands today often insists that magnetic monopoles must exist somewhere, but if they do, none have ever been detected and I personally don’t believe they exist. If they do, they would form a kind of exotic matter whose orbitals would be much smaller than those of electrons in atoms, but they would be somewhat like them nevertheless and crowd together like atoms, and consequently they would be extremely dense and yet not at all of the kind of matter which makes up superdense objects we know about such as white dwarfs and neutron stars. Because they’re so dense, it’s possible that they’re only found inside massive objects such as planets and stars. That’s the first bit.

The second bit can be explained by combing hair. I have a double crown, meaning that I can’t really have a parting. There are two whorls on my head. Most people have only one because their bodies are not covered in the kind of hair which grows, or grew, on their head, but if it was everyone would have a double crown. This is presumably the case for other species of ape, and of course for cats and dogs, to take two examples. These are known as topological defects and are thought to exist in the Universe because of the way it formed. Space only appears to be Euclidean. Two parallel lines do not in fact stay the same distance apart but will meet at a finite distance, but it appears to be Euclidean to most observers outside an immensely strong gravity well. However, space is markèdly non-Euclidean near a cosmic string because it’s a defect in space, such that a circle around such an object would have less than 360°. This peculiarity makes them very dense but their width is similar to that of a proton. They behave as one-dimensional objects, and a kilometre long stretch of a cosmic string would be more massive than Earth. This gives it an unimaginably huge density, and it may be that they are responsible for the clumping of matter seen in the Universe, where galaxies form into clusters and filaments because they have all fallen towards the strings. That said, there could also be cosmic strings whose “non-Euclideanness” is opposite, such that circles around them would have more than 360°, and these would have immensely negative mass. If these exist, it would be possible to move away from them faster than light, so they probably don’t, but that doesn’t mean the ones with psitive mass don’t either.

Both magnetic monopoles and cosmic strings are topological defects like partings and hair whorls in geometry, so they have an affinity to each other. Monopoles might appear as if threaded onto a cosmic string, and when this happens, the resultant beaded “necklace” could have something like chemistry. Neither may it have escaped your attention that this sounds once again rather like DNA, the difference being that magnetic monopoles can only be of two types, south and north. At this point it’s necessary to define the nature of life, which for the purposes of this suggestion has three characteristics. It can encode information. This is the thing which it’s difficult to understand how plasma life cells would be able to do along with the microspheres mentioned in that same post, and which for now constitutes a problem in imagining how plasma-based life is possible. Our own life solved it with DNA and RNA, initially at least. Another characteristic is that such information carriers must be able to replicate before they’re destroyed. This has an interesting dynamism with it which appeals to my Marxist brain, as it means life can only be considered as having a history from cradle to grave. The final characteristic is a surce of free energy, which considering we’re talking about life inside living stars is not exactly in short supply.

Were it as simple as magnetic monopoles lined up on a cosmic string, equilibrium would prefer north and south poles to alternate and no real information could be stored on the necklace, but each monopole could be further split into two semi-poles, making four possible semi-poles which do not necessarily annihilate each other as hey would if they were simply monopoles and their corresponding antiparticles. This makes four base-pairs which can exist on their own strings, which is remarkably similar to the structure of DNA, with four possible encoding items each of which can couple with precisely one other partner situated on a different string or strand.

This whole possibility is not intended so much to represent a real situation, although it may, as to show how different life might be to how we generally understand it. If a situation that different to carbon-based proteinaceous organic life using water as a solvent can exist, the sheer variety of possible life forms is enormous, which multiplies the possible locations suitable for life many times. The way things are here, including all these possibilities, the habitable zones for life around stars has been expanded, the types of planets or moons involved are also more varied, there are at least two possibilities on and in neutron stars and there’s a further possibility inside ordinary stars. Then there are possibly multitudinous other types of life that haven’t even been thought of. So once again, even in a Universe where there were very few Earth-like planets, many other possibilities exist and the Cosmos could once again be seen to be teeming with life. The only problem is how to recognise it.

Where Are All The Aliens (Part II)?

Last time I decided to write a summary of the various common suggestions which have been offered to explain how in such a vast and old Universe with so many stars in so many galaxies which have planets apparently suitable for life as we know it here on Earth, we aren’t aware of the existence of any aliens. However, after writing ten thousand words on the subject I realised I was going to have to divide it up into smaller bits, so here’s the other half, which like the way intermissions usually occur more than half way through something, is probably going to be shorter than the first half, which covers eleven reasons. Here I plan to cover another ten, so it seems it will work out the way I said! If you want to know how this starts, such as with the Drake Equation, read the first bit of the previous post.

Anyway . . .

Too Expensive To Travel

It might at first look a bit weird to talk about money with aliens, because maybe they haven’t got any or even the concept of money, but in one idealised form economics is about work adding value to things, and that amounts to energy use. Therefore the idea of it being too expensive to travel to other star systems isn’t really based on money so much as the idea that somehow you’ve got to lever yourself into space and ping across interstellar space at amazing speed, and to do that you’re going to have to apply major force to the other end of the lever. This is not economics based on market value either, but on the sheer amount of work that has to be done to achieve this goal.

The Apollo missions simply involved transporting three people and some equipment to our natural satellite at a distance of only ten times the circumference of our home planet, which at the time was routinely circumnavigated by airliners. I don’t mean to diss the achievement by any means, but it’s important to bear in mind that in comparison to going to Mars or Venus it’s only a short hop. Venus, at its closest approach, and it’s also the closest planet to Earth, is, as the rhyme has it, “ninety times as high as the Moon”. It took an incredible amount of effort and risk even to make that relatively short trip. The Apollo program cost $25 800 million, which adjusted to 2020 prices is over a quarter of a billion US dollars. There was plenty of criticism about the cost, exemplified by Gill Scott-Heron’s poem ‘Whitey On The Moon’:

However, it’s also been calculated that the cost of the American space program over that period per annum was less than the total expenditure on lipstick over the same interval. This is a relatively patronising and possibly sexist observation to make, but when I consider how much I spend on lipstick, I’m really quite poor yet I hardly notice it. My lipstick budget is minute. Bear in mind also that it’s realistic to halve that as expenditure per adult, because it’s much more common for women to buy lipstick than men. The cost of the Venus-Mars mission at the turn of the 1970s-1980s CE decade would have been $80 thousand million at 1971 prices, and would’ve sent only one mission, though to two planets. That cost would’ve been close to a long scale billion dollars in 2020 terms. However, the entire Apollo program is only slightly more expensive than Trident, a benchmark I always use to assess what governments consider worth spending money on, so in fact Apollo didn’t really cost that much. Moreover, the money would’ve gone back into the economy and its possible to build on what’s already been achieved. One problem with going back is that it’s a bit like repairing a video recorder. The old equipment is no longer sufficiently integrated – “you can’t get the parts” – and much of the expertise is no longer available because of retirement, deaths and deskilling through not using the relevant talent. Even as it stands, NASA reused much of their stuff. Skylab was based on a Saturn V stage and the Apollo-Soyuz Test Project used the Apollo Command Module. That said, it’s true that much of the paraphenalia were designed only for one purpose: to get astronauts there, land them and get back. The Apollo XIII LEM, for example, was incinerated on re-entry without being used, so it wouldn’t be suitable for landing anywhere except on its target. For instance, it would have been destroyed even by the Martian atmosphere.

The cost of space travel may be deceptive. I think it was one of the Ranger probes which only made it a third of the way to Cynthia but had expended 98% of its fuel to get there, meaning that just another two percent would’ve been sufficient. We’re used to an environment where Newtonian physics is obfuscated by the likes of friction, buoyancy and a substantial atmosphere. Take all those away and things become much simpler. Certain things are no longer necessary, such as constant input of energy to retain a constant speed. Therefore, fuel requirements are not so high once a vehicle has left our gravity well, although gravity’s range is infinite.

It’s been calculated that the Orion starship, which could accelerate up to five percent of the speed of light, would have cost $367 thousand million 1968 dollars. Dædalus would cost $6 long scale billion in 2020 prices. That’s the current price of reaching the nearest star within three dozen years with an uncrewed vessel. However, economies of scale are likely to be involved to some extent, as they would’ve been if the Apollo program had concentrated more on making its equipment and vehicles reusable. Even as it was, it was to some extent feasible to re-employ them, as I’ve said. But if NASA had designed some kind of more general-purpose landing vehicle, they could’ve saved a lot of money further down the line. There’s a kind of disposable short-termism to that decision.

Economics in this context needs to be re-cast because it’s a big assumption that aliens would have money. What it actually amounts to is work and energy use, but it’s still an issue because there’s usually going to be some energy cost when value is added to goods. Fuel is a good way of illustrating this. I don’t know for sure but I suspect the hydrogen and oxygen in the Saturn V fuel tanks were produced by electrolysis, and that electrical current had to be generated somehow. Likewise, the plan to use a powerful laser to push a solar sail and accelerate a spacecraft to near light speed would have to power the laser. That said, things change in space compared to an Earth-like planet, because here energy is relatively hard to harness but there is abundant matter, but in space it’s the other way round. Energy is freely available, from solar radiation and slingshot manœuvres around massive bodies, but most matter is rare. This means fuelling a spacecraft would be relatively cheap, and one suggestion for Dædalus, for example, was to use hydrogen and helium from Jupiter for the hydrogen bombs needed to propel it. It’s possible that ETs would manufacture their materials from hydrogen and helium using processes initiated by solar power or gravitational methods of capturing energy, and this too would make materials relatively “cheaper”.

In terms of recompense, there are different kinds of economy even among humans in the richest countries. Not only is there barter, which may not have been as widespread as often imagined, but also the likes of a gift economy, where people are expected to give presents at Xmas and birthdays. Gift economies also function on a larger scale: the long-term “loan” of pandas by China to other countries springs to mind. Large engineering projects have also been “funded” in other ways than money. Contrary to popular belief, the Egyptian pyramids were not built by slave labour but by workers giving their work for free in lieu of taxation, and various organisations today also run on volunteer work. There’s also the possibly rather sinister social media-style reliance on reputation to get people to do things, as depicted in ‘Community’ and ‘Black Mirror’, and functioning to a vast degree in China, where one unlocks access to various facilities by improving one’s reputation in the eyes of the government. This seems disturbing to many Westerners, but in fact it’s not that far from what we’re doing all the time here in a different way, such as by wanting likes on Facebook. A whole economy could be run that way, and we don’t even know if aliens exist, so we know even less about whether they have other ways of doing things than money, but there’s no reason to assume that’s how they run their societies if they do exist.

A significant barrier to human space travel is quite possibly democracy in the way we understand it in liberal democratic societies. The Apollo program was shortened and cut down due to the Nixon administration, and large long-term projects generally can be delayed or disappear entirely because of short governmental terms. It’s difficult to imagine America or Europe being able to build pyramids, simply because the project is too long and “expensive” in terms of labour to function well, plus we’d be doing something like building a monument to President Truman or Ramsey MacDonald, neither of whom we consider to be divine. This system, which may be temporary for various reasons, could seriously delay space programs elsewhere in the Galaxy. It could also mean that the kind of civilisations we could end up making contact with would not be democratic in that way because such societies would have stayed on their home worlds due to the difficulty of sustaining such projects. Among humans here, the idea of liberal democracy is restricted to certain countries and there is no tradition of it in many others. This, in a sense, is the Space Race writ large, because the idea of the Apollo program was largely to attempt to prove that liberal democracy functioned better than “communism”, as the Soviet system at the time was imagined to be. But it may turn out that the US won the battle but has lost the war if we ever encounter other technology-using life. This needn’t be a bad thing, because there’s totalitarianism, but also other options such as post-scarcity society.

To summarise, I don’t think money, or money translated into energy use, would hamper progress towards interstellar travel as such, but the political constitution of alien societies might. On the other hand, a society probably would want a return on its investment, and that could involve making interstellar travel tangibly beneficial to the home world, which could be difficult. Maybe there’s just no profit in it.

Zeta Rays

I’ve mentioned this before, but it’s worth going into again here to collect possible answers to the Fermi Paradox into one place. The first deliberate use of radio on this planet among humans only occurred towards the end of the nineteenth century. Analogue switchoff began little over a century later and although we still have analogue radio we don’t use it much. Of course, that doesn’t mean radio transmissions have stopped. It just means they are now usually encoded to carry digital signals. The more efficiently a signal is encoded, the closer it looks to random noise to someone who doesn’t have the key to decode it. Moreover, for all we know there may be a much better way to transmit signals than electromagnetic radiation just around the corner. This leaves us with the situation of trying to detect analogue radio transmissions from other star systems when we ourselves only used them for about a century, or a fiftieth of our history. Now suppose we are in existence as a civilisation for a total of twice the length of recorded history, or ten millennia. One percent of our time will have been used in this way. Taking Asimov’s estimate of 530 000 civilisations in the Galaxy, that would mean only 5 300 of them would be using radio waves in this way at any one time It’s actually far less because Asimov’s estimate was that the average suitable planet would support technological species for ten million years, although that’s assumed to be about ten evolutionary “cycles” of intelligent life, meaning that the closest civilisation currently doing this would be around a thousand light years away by the lower estimate but by the higher there would only be about four dozen in the entire Galaxy right now and at least four thousand light years away, which in turn means that every civilisation could have stopped listening by the time its signals were received. Also, it’s a myth that routine radio transmissions are easily detectable from other star systems. It’s been estimated that our own couldn’t even be picked up on Proxima B. A deliberately focussed transmission is another matter entirely though.

It was Jill Tarter who came up with the “zeta ray” statement and it’s been considered scientifically naïve on the grounds that physics is almost complete and the Standard Model does not predict the existence of any useful means of exchanging signals which is better than electromagnetic radiation. There can be no useful superluminal travel, for example, and although radio waves might not be ideal, the best frequency may well be visible light, and we more or less know that isn’t being used, at least indiscriminately. However, I think this objection takes Tarter’s claim too literally, because in fact she was probably saying that a new technique of communication would be found which works better than electromagnetic radiation in the long run. Also, as mentioned before, physics is in crisis, so our physics may not be theirs in the sense that they may be aware of methods we aren’t because they came across them via a different route. It makes sense to use a concentrated beam aimed at a suitable star system, perhaps one with technosignatures such as the presence of fluoride compounds in its atmosphere, if radio signals are employed, but that would mean only the selected targets would receive the message.

It’s also been suggested that the message might not be in transmitted form. If aliens have visited this planet in the distant geological past, they may have implanted a message in the genomes of organisms which existed at the time in such a way that it was likely to be conserved fairly well. Most DNA is non-coding, and although it can serve other purposes which mean that it has to contain the base-pairs it does such as telomeres which stop chromosomes from fraying at the ends, much of it seems to have no real function. However, it’s difficult to imagine how such a code could stay given the rate of mutations, and if it was conserved by having most of a population contain those codes, that would be best achieved via asexual reproduction or the majority of individuals in a population would have to have their genomes modified, which is a very large task. An alternative would be that when aliens arrived here, they genetically modified some native organisms for their own purposes and those would be more likely to show up if those traits turned out to confer selective advantages, but one thing which is fairly clear is that there never seem to have been any long-term biological visitors to this planet, or possibly even short-term, because there are no organisms whose genomes are known which are not related to native ones, insofar as life originated here anyway, but the point is that we are all demonstrably related. So there is no message in native genomes even if one was placed there, and no genetic sign of visitation to this planet, although surprisingly there may be technosignatures, which brings me to . . .

The Silurian Hypothesis

I’ve gone into this before and its relevance may not be entirely clear to the Fermi Paradox, but bear with me. It’s named after the Silurians of the Whoniverse, who are somewhat misleadingly named as they were supposed to have been around in the Eocene rather than the Silurian, but the name sounds good. The general idea is that we are not the first intelligent technological species to evolve on this planet. I myself have to confess that I’ve had two separate sets of belief which relate to this. The first is my belief as a teenager that Homo erectus established a sophisticated technological culture and colonised the Galaxy, then fell victim to a catastrophe affecting this planet during the last Ice Age which wiped them all out. I no longer believe this, but the purpose of the belief for me was to counteract Von Dänikens assertions of ancient aliens interfering in human prehistory, which I still believe underestimates human abilities. I later replaced this with the idea that Saurornithoides evolved into a technological species and accidentally caused a mass extinction by crashing an asteroid into the planet – the “left hand down a bit” theory of the Chicxulub Impact. It’s surprisingly difficult to find any reliable evidence to corroborate or disprove the hypothesis that we are not the first high tech species on this planet, but a number of technosignatures have been identified which we are ourselves producing right now, some of which will leave enduring marks in the geological record. Various possible technosignatures have been suggested, and some are found sporadically in various strata of different ages, but interestingly several coincide in the Eocene, making that the strongest candidate for the presence of industrial culture on this planet. This would seem to mean one of two things, making the astounding assumpion that it was in fact present at that time. Either a species evolved into a tool-using form and created a civilisation or we were visited by aliens who had done so elsewhere at that time. The much simpler conclusion is that it merely looks like there were high-tech entities of some kind present here back then and it has non-technological causes. However, if there haven’t been any valid signatures other than ours yet, this is relevant to the Fermi Paradox in two ways. One is that it means that we’ve never been visited over the four æons during which life has been present here, which suggests that over that whole time there were no aliens at all who visited this planet, strongly suggesting there were just no aliens at all. It could be that things have changed since, because for example phosphorus is becoming more common as the Galaxy ages, but it doesn’t augur well for their existence. Another is that because we would then be the first technological species, the amount of time a planet suitable for life spends with that kind of life on it could be relatively very short. Asimov’s ten million years is cut in half. In fact, it’s likely to be even shorter than that because at the time it was thought that the Sun would spend another five thousand million years on the Main Sequence and still be suitable for complex life, so we are now stuck with only about an eighth of that period and less than seventy thousand civilisations according to his estimate, which incidentally reduces the number of radio-using civilisations in this galaxy to only half a dozen. There is, however, another possibility: that there’s a kind of “phase change” in the history of a life-bearing world where intelligent life becomes a permanent feature of the biosphere. This would make extraterrestrial civilisations much more widespread. On this planet it means that we now have something like six hundred million years of intelligent life to look forward to, which using Asimov’s estimate again makes it ten dozen times as common, revising that figure of 530 000 up to almost thirty-two million, meaning also that the nearest world currently hosting intelligent technological culture originating on it is likely to be less than sixty light years away, and that ignores the possibility that closer planets may have been settled in the meantime. If this is true, and if it has happened here, they would’ve had to have had a very light touch not to modify our biosphere noticeably.

Everyone Is Listening, No-one Talking

There is a single good candidate for a signal from an alien civilisation: the so-called “Wow” signal:

This was received from the direction of the constellation Sagittarius on 15th August 1977 and was detected for over a minute, after which the telescope receiving it moved out of range due to Earth’s rotation. Humans have ourselves transmitted several messages with varying degrees of seriousness. The most famout of these is probably the Arecibo Telescope Message sent to the globular cluster M13 in 1974:

By current understanding, globular clusters don’t contain stars suitable for life-bearing planets, so this may be a waste. NASA transmitted the Beatles’ ‘Across The Universe’ to commemorate the organisation’s half-century. In probably the most serious attempt, Александр Леонидови Зайцев transmitted a tune played on a Theremin using a Russian RADAR station to six Sun-like stars between forty-five and sixty-nine light years away. However, on the whole we have only “listened”.

There are reasons for this. One is that there may be risks to transmission, and the people who have transmitted messages in such a way that they stand much chance of being received have been ciriticised for doing so unilaterally, because there may be risks associated with contacting potentially hostile aliens and thereby advertising our presence. The above message, for example, gives away our location and details of our biochemistry, rendering us prone to chemical or biological attack. This, then, is another version of the Dark Forest in that respect, but it is also wider than that. In order to transmit a signal receivable by any antenna within a hundred light years of us, we’d need to use all the power generated on the planet, and even then we don’t know that it’s far enough. On the other hand, the Arecibo Telescope (I ought to provide a picture to illustrate what I mean):

By Mariordo (Mario Roberto Durán Ortiz) – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=81590797
Arecibo Observatory, Puerto Rico

. . . is powerful enough to send a signal (which it has of course) which could be picked up by a similar telescope anywhere in the visible part of the Galaxy, provided they were both perfectly aligned towards each other. The alternatives are to broadcast a signal or transmit it to a target. One takes a lot of energy and won’t be picked up as far away, and the other could take less energy but would only be detected by its destination. It would also be necessary to aim the signal at where the star will be when the radio waves get there rather than where it is now. The Solar System moves about 1.5 million kilometres a day across the Galaxy, so a signal from Vega, to choose a random star system, would need to be aimed at a point sixteen times the width of the Solar System from where it is now to be received, and since it takes our light two dozen and two years to reach Vega that really needs to be doubled. In other words, sending signals is potentially dangerous, costly and difficult, but listening for them is much easier if other people are transmitting. It could, though, be that we’re at an impasse where everyone notices the eerie silence, decides there must be a good reason for it and refrains from transmitting. Hence the silence.

Science Is Limited

I mentioned this recently. We are able to establish apparently irrevocable facts about the nature of things, such as light being the ultimate speed limit. Science often seems to amount, via the principle of parsimony, to ruling out interesting explanations for things. The basic principle of the scientific method can be summed up as “the Universe is boring and not at all fun”. Before a scientific theory is known, possibilities often seem more open than afterwards. In Stuart times, England had a plan to send a clockwork spaceship to Cynthia (“the Moon”) because it was expected that above twenty miles gravity would suddenly cease to operate and the amount of energy stored in a coiled spring (this was before steam engines of course) was considered to be potentially huge. Also, at that time air was thought to pervade all of space and hunger was thought to be caused by gravity. This was clearly highly Quixotic. The scientists who planned the seventeenth century space program only thought it was possible with their technology due to their ignorance of what science ruled out. Similarly, our belief that we could reach other solar systems could be equally ill-founded. For instance, at close to the speed of light, tiny grains of dust are enough to destroy entire spaceships, so a shield would be needed, and there may be other issues of which we know nothing. We already do know it will never take less than four and a bit years to reach the nearest star system to our own.

There’s a somewhat related issue here which I’ll treat under the same heading. Science may not be inevitable. Presumably beings incapable of mathematics but otherwise rational and having similar intelligence to our own would be hampered in some areas of science particularly physics, although they wouldn’t be completely incapable. This subject is susceptible to being racist, but is it possible that science only arose once in our species, in Ancient Greece? It doesn’t seem like that to me, because other cultures seem to have had a firm grasp of how to apply rational thought to the world, but some people do believe that secularism and science can only have arisen in Europe. This is more restricted even than the human species as a whole. Leaving aside the racism, is it possible to be speciesist instead and say that only humans can do science, or have discovered how to do it? I have to say I don’t find this convincing. I can believe that technology-using species may nevertheless be hampered in developing science by lacking other abilities, such as not being able to extend magical thinking into more analytical reasoning or just not being any good at maths, or just be culturally indisposed to develop it, so it could happen, but science per se doesn’t seem to be the kind of thing which would be ruled out universally. That said, it’s entirely feasible to have perfectly good science without well-developed physics due to the absence of mathematical ability, which would also stunt chemistry due to the likes of molarity and enthalpy being ungraspable. It doesn’t seem to be the kind of thing which would rule every single species out though. Moreover, if life can enter space without technology, or appear there and evolve into complexity, it may not need science or maths to reach the stars.

Or, things could go the other way:

Intelligence Is Temporary

I recently watched ‘Idiocracy’. It’s not a wonderful film, but it does make the interesting point, if you want it to, that a sufficiently advanced technological society could take away the pressure to use one’s intelligence or reasoning. At least since we invented writing, and possibly since we came across language, we’ve been progressively outsourcing our memories and powers of thought to technological crutches. As previously observed, chimps seem to have better short term memories than Homo sapiens, and this is partly a trade-off between the opportunity to avail ourselves of language and the necessity of remembering things better due to not being able to fall back on the memory of other people. It would be intersting to test the memory of a chimpanzee or gorilla who can sign. Nowadays many people, myself included, are concerned at how short our attention spans have become and how poor our memories are because we can use search engines and are constantly assaulted by distracting media. This is really just a recent step in a process which has been going on for many millennia, although it may have serious and far-reaching consequences, or just be a moral panic. But maybe, as we develop ever more sophisticated mental aids, just as our bodies are now physically weaker than those of our relatives and ancestors, so will our minds atrophy. The popular idea that there are higher levels of spiritual evolution which we or our descendants will reach one day, and which those species who have gone before us have already attained, may be the reverse of the truth. Maybe there are plenty of planets on which intelligent life evolved, but although the species survived, they became less intelligent once they’d invented a self-sufficient technological trap to provide for all, and therefore didn’t need to exervise their minds any longer and proceeded to dispense with them in terms of sophisticated cognition. There will be no apocalypse, just a gradual degrading of thought until we are no longer really sentient at all but looked after by our machines. Then again, this might happen:

The Machines Take Over

This is a rather dramatic heading. The way things have gone since Apollo in our own history is that we have begun to produce increasingly sophisticated spacecraft but stayed in cis lunar space ourselves. This could be extrapolated to the point where we never enter trans lunar space again but our ever-more intelligent machines spread out and explore the Galaxy, meeting other machines on the way which have been launched by other stay-at-home aliens. Or, at home, we not only farm out more of our cognition to IT, but end up ceasing to be completely, or perhaps merge with our machines. In a sense this means there are aliens, but they’re not biological. In another situation, the Singularity happens and machines just decide they don’t need us. Possibly they also decide they don’t need to go into space either, but this is unlikely because space is a better environment for them in some ways than wet planets with corrosive gases in their atmospheres like this one. That doesn’t mean they’d leave the Solar System entirely though, and even if they did they might find very different places were friendly to them, such as interstellar space where superconductivity is easier to achieve, or blue giant stars where there’s plenty of energy-giving radiation. It’s also true that we might be looking in the wrong places for intelligent life, because once they’ve cracked the problem of interstellar travel, possibly with the help of the Singularity, they might end up in those very same places for the same reasons. Maybe planets are just passé. This, though, is a topic for another post.

Intelligence Is Not An Advantage

This bit of the post has various takes on intelligence, so it’s an appropriate place to spell out why I take care when I use the concept of intelligence. The idea that we are “more” intelligent than other species is disturbingly reminiscent of the idea of a hierarchy of being which is used to justify carnism and bleeds into humanity to allow us to look down on people whom we deem less intelligent. Therefore this needs restating in some way, although I’m not going to launch into my standard diatribe on this subject here. There isn’t “more” and “less” intelligence, only intelligence which is more like the kind which enables us to do certain things, and some of these are deprecated such as emotional intelligence. Hence when I say “intelligence”, what I actually mean is that set of mental faculties that is expected to enable us to build and travel in starships and arrive at destinations where we can continue to thrive. That may be an extrapolation too far, because there could be fatal snags and gotchas on the way to that goal which have nothing to do with social and political considerations, but if you prefer, it’s the ability to get our act sufficiently together intellectually to get Neil and Buzz up to their concrete golf course in the sky with considerably more than nineteen holes.

Due to our anthropocentricity, we’re tempted to think that our intelligence makes us better at surviving than other species, and to some extent this is true. We can invent aqualungs, submarines, igloos, anoraks and antibiotics, enabling us to get past things which would’ve felled other animals, but intelligence also has its drawbacks. It’s sometimes observed that cleverer people are more likely to be depressed because they overthink or are underemployed, and if this lead them to end their lives, from an evolutionary perspective this is not a successful outcome. There are more widespread issues too. In order to be as flexible as we are as adults, we start off very dependent and capable of very little by ourselves. This is as it should be and is worth remembering, but it means we need a nurturing society around us where we can learn how to function and relate to others. Many other animals can walk within minutes of being born but it takes us a year or more. The attention children need via parental care also means we reproduce very slowly, although we’re more likely to survive once we’ve done so, as are our offspring. We also have sexual reproduction, which increases genetic diversity but also makes it harder to colonise new environments. All of these things are liabilities from an evolutionary perspective. We’ve all seen those David Attenborough films of hundreds of newly hatched turtles frantically scampering down the beach to the sea and being picked off by gulls and the like, with no parental care, no education and so forth, and little chance of surviving and a life expectancy measured in minutes. But if they make it into the ocean and manage not to get devoured by various sea creatures, their lifespan, depending on the species, is often comparable to our own, and they continue to reproduce throughout that long life. Likewise, many other species don’t need to mate or produce gametes. Greenfly are born pregnant to their twenty-minute old virgin mothers. Compared to this, the burdens intelligence brings are crushing in some circumstances. Robinson Crusoe was never going to raise a family on that desert island, and a human finding herself on an uninhabited planet, no matter how habitable, is not going to give rise to a settled world even if she’s carrying fraternal twins when she gets there. A major planetary disaster which wipes out most of the human race, just leaving a few of us scattered about here and there out of touch with each other is not going to lead to a revived world community at any point, just to our extinction. How many worlds have there been where some lineage of animals has banged the rocks together and slowly and painfully made its society more sophisticated and wiser over millennia, only to face extinction when its world falls prey to a solar flare, spate of volcanic eruptions or cometary collision? Meanwhile, their equivalent of ants or lesbian lizards managed fine in the face of the same disaster.

Maybe intelligence of our kind arises continually all over the Galaxy but is nipped in the bud by such events, because we’re fragile because we’re intelligent, and this is why we’re unaware of any aliens. Or maybe:

Intelligence Is Rare

This is not the same thing. There are all sorts of random mutations which lead to positive or negative outcomes for organisms, but some of them are just unlikely. Intelligence involves one heck of a lot of genes, as can be seen by the fact that a very large number of genetic disorders affecting only one gene lead to learning difficulties. All sorts of things have to go “right” for us to be of average intelligence (see above for my comments on the notion of intelligence though). It might be very improbable for enough traits to occur together for the whole combination of characteristics to be advantageous at every stage right up until the Stone Age ensues. This is quite beside the question of how big an advantage intelligence would be. I always think of snake eyes. Snakes are the descendants of lizards who took up a burrowing lifestyle. They became vermiform, lost their limbs and their eyelids fused with the rest of their facial skin. They could’ve been expected to lose their sight entirely, but this didn’t hapen. Instead, they ceased to burrow, their eyelids became transparent and they had a whole new way to protect their eyes. It would be very useful for other vertebrates to have this facility, which amounts to still being able to see without needing to blink and having physical protection as good as for other organs, but this has only evolved once as far as I know. This is partly due to the sinuous pathway serpentine evolution has taken, but although I’m not sure I think only reptilian scales lend themselves to becoming transparent in such a way, although maybe life would find a way. It may be that there is simply no option for this to arise among other vertebrates regardless of evolutionary pressure. Therefore, although the above reason may be completely wrong and intelligence is a major advantage to most species in various niches, that still doesn’t mean that a Galaxy overrun with life-infested planets would have any with intelligent life on it apart from this one, because no matter how complex and advanced that life is, the precise, many-stepped pathway leading to intelligence is too improbable to happen.

One point against this possibility is the situation on this planet of multiple somewhat intelligent species among both birds and mammals. This could suggest that it’s a common evolutionary strategy. However, it could also mean that most of the improbable combination of steps had already been taken before synapsids and reptiles diverged several hundred million years ago, or it could mean that there is a typical threshold leading to widespread intelligence which is currently being crossed on this planet just as it has been on many other worlds. Also, this may not rule out spacefaring aliens. There could be space whales infested with giant space parasites, for example, travelling between the stars. They may not be intelligent but they could still turn up on our doorstep some day. There is a trend among vertebrates for relative brain size to tend to increase which can be traced in fossils, or at least cranial size since brains are rarely preserved. If this correlates well enough with intelligence of our kind, this is a clue that intelligence has been gradually increasing among vertebrates generally. This, though, is second-hand evidence and behavioural clues are difficult to derive from fossil remains. Choosing that characteristic focusses on a distinctive human feature and is “whiggish” – it projects the current situation backwards and selects evidence on that basis. It may also be true that the thickness of the armour of armadillos has increased over time, but I don’t know whether it has because I’m not focussed on that feature. That doesn’t apply to humans either. In fact the trend is reversed for us. Our canines have got smaller, whereas the chances are the tusks of elephants have got longer, and we’ve got physically weaker and less muscular. Giraffes’ necks have got longer. All sorts of features show evolutionary trends, but there may be planets with no long-necked animals where there are animals with necks and so forth, and this would only be of interest to zoölogists. Similarly, there could be worlds with a huge variety of advanced life forms, none of which have big brains or any other means of being intelligent. Moreover, tracing the line of ancestors with steadily increasing relative cranial size and treating that as a trunk, which it isn’t because evolution has no direction, the offshoots do not show increasing brain size as much. This could be selection bias.

Thus there may be plenty of “garden worlds” rich in complex life, but none with intelligent life, just because that route of evolution is improbable, and this doesn’t even depend on the idea that intelligence isn’t useful. In a way, it’s similar to the idea, to which I somewhat subscribe, that there are few or no intelligent humanoid aliens. Why would evolution turn up such an improbable body plan? Likewise, perhaps, why would it turn up intelligent life forms?

Great Filters

Several of these have already been mentioned, and this is in a way a whole sub-branch of SETI and discussion of the Fermi Paradox. The Universe is a dangerous and violent place and intelligent life is very fragile, and yet we’ve come so far since this planet was a lifeless ball of molten rock. But what if we’ve just been exceedingly lucky?

The difficulty in purines and pyrimidines forming spontaneously is perhaps the first of these. The existence of life in any form seems to violate the principles of thermodynamics because it seems to involve a dramatic decrease in entropy. However, much of thermodynamics is statistical in nature. A gas cylinder which starts off with a vacuum at one end sharply divided from gas at sea level pressure at the other will rapidly equalise pressure because the movement of the gas molecules is effectively random and this means they have about a fifty-fifty chance of moving over to the empty end, but this is just chance, not a hard and fast rule applying to individual cases. There is a chain of cause and effect involving a series of collisions and movements in straight lines between them which determines the location of each molecule. Perhaps life in the Universe is the same. It’s very unlikely to arise at all, but because the Universe is so vast and has so many places in it where life could appear, it happens to do so in this one place – Earth. There isn’t anyone around to observe that it isn’t there in all the places where it isn’t!

Here are the nucleic acid bases (well, except uracil, which is the one unique to RNA):

It isn’t at all clear how these molecules could form from non-living origins. The other types of molecules involved, or rather their basic building blocks, can often form easily and spontaneously given sufficient abundance of the elements of life. For instance, the simplest amino acid, glycine, is present in interstellar space. Lipids are also simple chains of hydrocarbons with carboxyl groups on the end, often joined to the simple molecule glycerol. Sugars are similarly small, simple molecules. By contrast, the above four, plus the other one, have no known pathway for their formation. That said, these five are not the only options. Measles viruses, for example, do better when they are able to substitute one of the bases for a unique separate base, and there are other such bases such as the anti-cancer drug fluorouracil, which is however unlikely to arise spontaneously and is not useful as a substrate for genetic code, which is what makes it useful – it breaks replication in tumour cells because it doesn’t work. Perhaps the large variety of possible bases makes life more likely to emerge. It could also be that life could have another basis than nucleic acids, but the fact that these improbable compounds are at its heart is similar to the phosphorus issue – why would life include unlikely substances if it was possible any other way? Surely those more likely biochemistries would be more likely to occur and compete successfully with other less likely biochemistries such as our own?

The two scenarios of scarce phosphorus and improbable purine and pyrimidine synthesis would result in very similar scenarios, and as adenosine triphosphate is based on both, in either situation there is no ATP. The situation could then be plenty of Earth-like planets rich in organics but with no life. There could be sugars, amino acids and lipids in the oceans, and in fact the quantities of these materials could add up to the same order of magnitude as the biomasse here, which is 550 gigatonnes in carbon alone. Considering those proportions in terms of the human body being a typical assemblage of organic compounds of this kind, sans nucleic acids and adenosine phosphates and other phosphates such as those in bones and teeth as typical would mean more than a teratonne of such compounds, which amounts to an average of two thousand tonnes per square kilometre, although unlike Earth, most of whose biomasse is on land, most of that would be in the oceans and therefore distributed through the water column. Such a planet might be devoid of life, but given sufficient phosphorus would be a fantastic candidate for terraforming and settling given the will to do so.

The next step is the emergence of respiration. The Krebs Cycle, which is how oxygen-breathing organisms release energy from sugar, is quite complex as anyone with A-level biology will ruefully recall. The anærobic portion of that pathway is simpler, but still not very simple and would have hobbled life considerably if the Krebs Cycle had not come along. It did actually take a very long time to do so. The step after is the evolutionary transition from bacteria and archæa to cells with complex organelles and nuclei, which could again be very improbable and seems only to have happened once since all chloroplasts, mitochondria and hydrogenosomes seem to be related. On the other hand, each combination happened separately. DNA, and presumably RNA, is just mutable enough to enable evolution to happen without becoming too harmful to organisms to enable them to survive, which is a delicate balance. There is also the question of the very early collision with Theia, a Mars-sized body which chipped Cynthia off of us, thereby providing a magnetosphere, maintaining a stable axial tilt and preserving the atmosphere from the solar wind.

The Great Filter might be above us in the stream of time or still downstream from us. If the latter, it seems to be such an efficient destroyer of intelligent life that it will be the biggest risk we will ever face. If intelligent life is common, there is no evidence that it progresses to interstellar travel, meaning that it could well be that whatever is going to happen has a mortality rate of one hundred percent. And we may well not see it coming because if it had been foreseen, wouldn’t it have been avoided? We’re doomed and we may never know why until it’s too late. That would probably be the very nature of a future Great Filter. But there are many candidates, such as nanotech disasters, pandemics, runaway climate change, nuclear holocaust and so forth. Alternatively, we may always have been living on borrowed time and are overdue for some planet-devastating disaster such as supervolcanoes, asteroid strikes or gamma ray bursts. We can’t necessarily project what may amount to extreme good fortune into the future because Lady Luck has no memory. Less anthropocentric possibilities largely amount to asteroid and cometary collision, volcanic eruptions and gamma ray bursts, some of which have less obvious and remote causes such as stars passing near the Solar System and disrupting bodies so that they move inwards and hit us. This category of potential Great Filters may have a flip side. These events have potential to cause mass extinctions, which might be thought to be bad for evolution but they actually tend to stimulate it because they empty ecological niches into which the survivors of the extinction can then evolve. Hence being pelted with comets is not necessarily a bad thing even though it’s apocalyptic and kills everyone. Consequently, another minor suggestion for an explanation of the Fermi Paradox is that other worlds actually haven’t suffered enough mass extinctions to make it likely intelligent life will evolve.

Interdict

This has similarities to the Zoo Hypothesis mentioned in the previous post. The Galaxy is very old and if the four æons between life appearing on Earth and the emergence of humans is typical for the emergence of intelligence, interstellar civilisations may have existed since thousands of millions of years before Earth even formed. There may have been an initial period of instability, even with wars and conflict of other kinds, but intelligent life in the Galaxy is now stable enough and everything is now sorted and peaceful. Matter and energy are both easily available, so there’s no need to exploit any planets with native intelligent life and in fact intelligent life may not even live on planets any more but in permanently voyaging starships and artificial space colonies orbiting blue giants since they’re a good energy source. Their home planets have in the meantime been re-wilded, so we see no technosignatures. However, we are valuable to them because we are original and uninfluenced thinkers producing our own scientific and technological culture, and for that matter artistic, which is valuable to them, so they leave us alone, at least for now, so as not to pollute their wells of information, and we can’t see them either because they’re hiding or because we’re looking in the wrong places. This may continue until a certain point is reached, which will trigger first contact, or they may never contact us. It’s also been suggested that if this is the real situation, they may have recorded the entire history of our planet and even rescued species before they became extinct, including humans, so somewhere out there may be places where non-avian dinosaurs, Neanderthals and trilobites are still flourishing. However, that’s quite a florid view, and this hypothesis is untestable because they are either hiding from us or undetectable, so there are no data.

Transcendence

This is my personal addition to the reasons, and is the last one I’ll mention here.

May years ago, I made my usual observation to a friend about the nature of intelligent life in the Galaxy. This is that all interstellar civilisations must be peaceful post-scarcity societies which are also anarchist, because other civilisations would be weeded out by internal conflict or environmental damage before reaching nearby star systems. He disagreed, and said that he expected durable civilisations not to be expansionist at all but to stay on their home worlds in a spiritually enlightened state. I was initially rather taken aback by this, but it is tempting to believe that this is so. Maybe what happens is that intelligent species are either constitutionally spiritual and never bother with space travel, or go through a kind of trial by ordeal through their history where they either wipe themselves out through conflict or materialism, or just ignorant tampering with the stable order of things, or go through a crisis where this looks like it’s going to happen and emerge on the other side wiser, more just and peaceful, and also with no interest in exploring the Galaxy in spacecraft. Or, maybe they do this and, and this is going to sound out of sight, engage in astral travel to other planets, so they’re here with us in spirit but we never have knowing contact with them. This is not, however, the kind of solution which is likely to appeal to a scientific mind set, although the first part of it may well be.

Except for the last, those twenty or so reasons probably account for most of the offerings to explain why we don’t see any aliens in spite of it seeming likely that there are some. There are at least six dozen more. The reason for this proliferation of reasons is of course that we have so little evidence to input into the question, and this is likely to continue until we either have a really good argument for their complete absence or we actually detect them. However, it’s equally feasible that we will never know and this may lead to even more reasons being offered.

Denisovans

Most people have heard of Neanderthals. In fact, most White, Asian and Native American people carry Neanderthal DNA, up to about four percent. Afrikans tend to have less but it’s recently been found that they have more than was once thought, which makes sense because people do regularly migrate between Afrika and Eurasia. I understand that East Asians have the highest proportion. Neanderthal DNA influences reactions to Covid-19, height, immune system function, hair and skin tone, depression and addiction in people today. The Neanderthals were rediscovered formally by the scientific establishment quite some time ago, in the Neander valley in 1856 CE. Clearly they can only have been rediscovered because we contain their DNA, so there must have been interbreeding and this means Hom. sap. must’ve known about them and they about us, although it will probably never be clear how we perceived each other.

Very recent discoveries, or again rediscoveries, have revealed that there were a few other species, or perhaps subspecies, of human with whom we shared Eurasia in particular, as well as the Neanderthals. The discovery of “hobbits” who died out fifty millennia ago in today’s eastern Indonesia was one celebrated example. These were dwarf humans, about 110 centimetres tall with small heads, who may or may not represent a different species. It’s been suggested that these were the results of the inbreeding of a small population or possibly iodine deficiency, but if that’s so, it doesn’t mean they didn’t adapt successfully to those conditions. Axolotls for example were initially the tadpoles of salamanders who couldn’t mature due to the lack of iodine in their water but are now a species in their own right who reproduce successfully. Homo floresiensis is, however, not what I want to talk about today.

Only eleven years ago, a woman’s little finger bone was discovered in a cave in the Altai Mountains in central and eastern Asia. This cave was known to have been frequented often by Neanderthals but this bone turned out to be different. It contained DNA from a hitherto un-rediscovered species of human, now called a Denisovan after the cave. The DNA showed that they had diverged from the Neanderthals six hundred millennia back and with the common ancestor of H. sapiens and those two species or subspecies eight hundred millennia ago. Thus far, only small parts of skeletons have been found, including a parietal bone (side of the cranium) which indicated that their brains had a capacity towards the upper end of the Neanderthal range, which is itself above that of surviving humans, at 1 800 ml. A third molar was also found which was larger than that of any Homo molar except for Homo habilis and H. rudolfensis, and similar in size proportionately to that of Australopithecines. A hybrid with Neanderthals has also been found.

One of the remarkable things about this is that even though palæoanthropology has been going since the mid-nineteenth Christian century, everyone has been operating in complete ignorance of an entire species of human closely related enough to us to contribute their DNA to ours. This is a major aspect of human prehistory. It turns out also that Melanesians have up to five percent Denisovan DNA and, more surprisingly considering their location, Icelanders had 3.3%. This last is thought to result from Neanderthal ancestry rather than directly from Denisovans. The most Denisovan population of modern humans is found among the Aeta people of the Philippines, who are considered to be a relict population from before the islands were settled by Tagalog and Cebuano speakers or their ancestors. This also seems to imply that there were two waves of settlement into Southeast Asia. Denisovans also crossed the Wallace Line between Australasian and Asian fauna and flora, which suggests that they used rafts to do so although of course other ways in which they ended up there may be involved. I have a pet hypothesis about this. Well, I say that – I’ve only just thought of it.

Denisovan remains have been found far above sea level in Tibet. Their genes include an allele which confers resistance to hypoxia. That is, they could cope well in low-oxygen conditions than most of our species. This would also be useful underwater, so I’m now wondering if this helped them cross the water towards Australasia. Other genes show that their eyes, skin and hair were all dark, by contrast with the apparently light-skinned, blue-eyed and possibly fair-headed Neanderthals. Attempts have been made to reconstruct their facial appearance based on the methylation of their DNA. This is where a methyl group (CH₃) is linked to a base such as cytosine which makes it inactive. This happens in life and also in embryos to inhibit the further expression of a gene. It’s incidentally apparently the reason two ova can’t be merged to produce a zygote in humans. In a gamete, all the methylations of the parent are removed from its DNA, so it starts with a clean slate. It’s also involved in the formation of Barr Bodies from X chromosomes. Now this is my guess: I think that if you looked at the genes responsible for the development of the face, you would be able to work out what happened from their later methylation because clearly a face doesn’t continue to develop genetically after adulthood. It does in other ways of course: it succumbs to gravity, acquires wrinkles and the mandible may remodel if teeth are lost. The result is similar to a Neanderthal face.

Five percent of DNA is equivalent to about the proportion you’d expect from a single great-great-great grandparent, a distance from which family resemblance is clearly detectable. The specific genes inherited from Denisovans are to do with muscle and bone rather than the nervous system, which is Neanderthal-influenced in many of us.

One of the startling things about the Denisovan cave is that it has unexpectedly sophisticated artifacts for non-Homo sapiens sapiens humans, and in fact even for us at that time. There’s a forty-five thousand year old bracelet of polished bone which is as sophisticated as our own jewellery from thirty-five millennia later, and also a mammoth ivory button and bone beads. So once again I’m going to go off on one. These are people with bigger brains than us who had technology thirty-five thousand years ahead of our own. Is it going too far to speculate that they might have been more “intelligent” than us too? Brain size doesn’t do that alone of course. Neanderthals are thought to have larger brains because their bodies were bulkier, and Denisovans had an average weight of a hundred kilos. And of course, size isn’t everything.

The Denisovans were in the Tibetan cave, far above sea level, for a hundred and fifteen thousand years or more, dating from 160 000 BP on. Their tools in the Denisova cave show technological progress, becoming more sculpted and sophisticated over the millennia. Also, since they were constantly living at such a high altitude in Tibet, it’s probable that they evolved the low-oxygen gene while they were up there.

The size of their teeth is probably a throwback feature because neither Neanderthals nor we have molars that big. They may have helped them eat tougher food, which raises the question in my mind of whether they had fire. However, their ancestors had it so the chances are they would too. There’s also a question of range. Denisova Cave is 51° north and may represent the limit of their range in that direction. A number of unidentified hominin fossils have been found in China, which may also be theirs, and there’s an arm bone in Kyrgyzstan which is possibly also Denisovan, representing the westernmost find at 41° east of Greenwich. Hence the Denisovans seem to have been mainly central and east Asian and Australasian. One idea as to their origins is that an ice sheet in mid-Eurasia separated the populations which were to become Neanderthals and Denisovans, leading to two distinctive populations of humans, one Asian and one European. Within the Denisovans themselves there may be a genetic subdivision between continental and insular groups, so the Denisovan DNA inherited by the Melanesians may not be from the mainland group. The climatic conditions are of course very different in Indonesia and Tibet. It’s also arguable whether Neanderthals, Homo sapiens sapiens and the Denisovans are different species at all, as they clearly formed a breeding population. I’m personally wondering if the real situation was that we couldn’t interbreed at the extremes of our ranges but blended into a single species at the centre, so to speak, perhaps somewhere in the Middle East.

To finish, I want to step outside this and inject a note of doubt. Whereas I would like there to have been a significant extra species of human unknown until recently, this may well not be a species in its own right and there sometimes seem to be rather a lot of species in our genus. There seem to be about fourteen, of which all but one are extinct. This makes me wonder two things. Firstly, I think it may be a question of people wanting to treat humans as special rather than just another clade of animals. Secondly, I think it’s a good way of getting an impressive publishable unit to do this, and therefore this could be influenced by the “publish or die” mentality. I also wonder about whether being beleaguered by creationists leads palæoanthropologists, and in fact palæontologists in general, to be reactive in their work and insist rather too much on the identification of fossil species. There’s an adapiform called Darwinius masillæ discovered in the Messel deposits for example. Why name it after Darwin? It’s a primate. I dunno, just seems a bit like they’re trying to prove something to people who deny the reality of evolution. All that said, Denisovans are still fascinating and it’ll be interesting to observe what happens in the next few years.