On this blog, I’ve often mentioned the tendency and the temptation to look at the past as if it’s just a prologue to the present. If that’s so, that would surely make the present a prologue to the future, which seems silly. In fact the past was the way the present used to be and we should appreciate the past in all its pastness. I sometimes joke that all the years after 1984 CE are just made up, because that year seems to be the peak of my reminiscence bump.
Consider, then, the above image. I can’t say I’m fully aware of every species of animal in it but I suspect that some of them are only included because they’re close to the ancestors of species we’re familiar with today. For instance, I spy tiny horses, but back in the day Hyracotherium wasn’t a tiny horse waiting for the grasslands to develop so she could get bigger and gallop across them as some kind of vaguely hare-like animal living in the leafy undergrowth of the rainforests, even though their children’s children’s children’s . . . children would be horses, zebras and donkeys.
The above scene is from the Eocene. This used to be thought of as happening immediately after the Chicxulub Impactor led to the deaths of all but the smallest dinosaurs, but nowadays the Palæocene has been inserted between that incident and the start of the Eocene, so it’s now seen as starting later than it used to be and doesn’t have the specialness of being immediately after the big kablooie. Because of the older idea that the dinosaurs (who used to be decidedly non-birdy) were cold-blooded and had died out because of climate change, i.e. it got too cold for them and they all died of hypothermia or something, I used to think of the Eocene as kind of cold and rainy. After all, if “warm-blooded” animals like mammals and birds were able to thrive during it and the dinosaurs, being cold-blooded, couldn’t, it seems to make sense that it was not very warm.
In fact, the opposite is the case. The Eocene was ludicrously and stupendously warm. It was so warm that there were tropial rainforests in the Arctic and the polar ocean was like a warm bath in temperature. It was hotter than the age of dinosaurs by far, and even in 24-hour darkness it stayed warm enough for there to be hot, steamy jungles. I find this utterly confounding, because in such conditions mammals would seem to be at a disadvantage compared to reptiles. They’d be expending loads of energy just trying to keep themselves cool enough not to succumb to heatstroke. Then again, maybe this is the answer. The reptiles maybe didn’t do so well because they were heated by the ambient temperature, whereas mammals were better at keeping their temperatures lower. Maybe the truth about mammals is that far from being warm-blooded, they were actually cold-blooded, in that they were kind of living self-refrigerators, and it was this which enabled them to survive such a sultry planet. But it still doesn’t make much sense to me, particularly because the lack of daylight which went on for months at a time at the poles still didn’t make it cold.
That, then, is one major odd thing about the Eocene, but it isn’t alone and it isn’t the only weirdness. The fact is that of all suspect times in the planet’s history, the Eocene is the best fit for the Silurian Hypothesis. If you just want a breakdown of that in general, feel free to follow the link, but the basic idea is that because we have quite good evidence for how our own civilisation is affecting the planet, we can look back into the past and find other times in the geological record where something similar happened, and perhaps conjecture that the reason it did so was that there was an advanced civilisation on Earth at the time. There are a number of candidates for this idea, but by far the best in terms of several different technosignatures coinciding takes place during the Eocene.
A technosignature is a sign, perhaps observable from another star system, that advanced technology is or has been in use on a particular planet or in a particular star system. It might be something like a planet with fluorine compounds in its atmosphere or an unusually high level of carbon dioxide as well as oxygen. I’ve just made those up by the way. At the moment, something a little suspicious has been noticed in stars near Tabby’s Star which may be along these lines. Tabby’s Star is a star with an unusual pattern of dimming which it was tentatively suggested might be evidence for a megastructure such as a Dyson Swarm around it. Simpler and better explanations have been offered for that individual star, involving dust and unusual but feasible patterns of comets, but it’s more recently been found that the pattern is found in stars near Tabby’s Star itself which are exactly the types of star expected to be suitable for life. Although it’s strongly tempting to imagine an interstellar civilisation based on this, this can amount to “a wizard did it”, i.e. it’s the go-to explanation for anything unexplained, and it’s not boring enough to be true.
The Silurian Hypothesis is named after the ‘Doctor Who’ monsters known as the Silurians. Perhaps coincidentally, these don’t date from the Silurian itself, although the name sounds cooler, but from the Eocene. They hibernate for millions of years before emerging from their slumber to find the mammals have taken over, so they actually belong here and are not aliens, but as befits the pulpy nature of Who, which it’s no worse for, this is all a bit thrown together like that bit in ‘City Of Death’ where life is supposed to have begun 300 million years ago rather than over ten times further back than that. But I can forgive that because it’s by Douglas Adams. The Silurian Period itself was before vertebrates had heaved themselves out of the water, or rather found themselves in increasingly shallow deoxygenated water until they were just squelching about in mud, so it doesn’t seem to lend itself that well to a race worthy of the name, but is actually named after a Pre-Roman Celtic tribe native to what has become Southeast Wales. It also happens to be found in the zoölogical name for catfish, the siluriformes, and the idea of vaguely vertebrate-looking aliens with tentacles on their faces instead of hands is quite appealingly exotic and perhaps creepy, but Doctor Who Silurians don’t look like that at all.
This subject is kind of about aliens, but in another way it isn’t. However, the circumstances of the Eocene suggest that if something did happen then it wouldn’t have originated from this planet, because it doesn’t look very promising. The non-avian dinosaurs, which had reached some kind of climax, had just been wiped out (fifteen million years is not necessarily a long time geologically) but the placental mammals hadn’t had time to get very far yet. The Eocene placental mammals were very diverse, because evolution had enabled them to radiate into the newly vacated ecological niches very fast, but there would later be a reckoning leading to most of those groups becoming extinct. Therefore it doesn’t seem very likely a technological civilisation would appear among them.
It should also be borne in mind that the Eocene is a long stretch of time compared to human history, from 56 to 33.9 million years ago or more than twenty-two million years. Taking the persistence of behavioural modernity as the starting point of our history (the likes of cosmetics, jewellery, cave art, burial customs and so forth), five hundred centuries ago, this is over four hundred times as long. Thus the geological record of a prehistoric civilisation would be quite short and abrupt.
I don’t want to repeat what I said in the original article here because my focus is a bit different, but for convenience’s sake, what we will leave in the geological record is a mark of the damage, though temporary, we’re doing to the environment and there are a number of possibilities. Firstly, light elements cycling through the biosphere and other cycles without technological intervention have a distinctive isotopic profile because they’re exposed to solar radiation and this changes the number of neutrons in their atoms, whereas the same elements buried deep underground are shielded from this by layers of rock which block the same radiation. Hence the nitrogen in fertilisers which has been mined rather than, for instance, being derived from guano as is traditional has different proportions of isotopes in it. The carbon implicated in anthropogenic climate change is also different because it was taken from coal and oil. Although many isotopes are unstable and will have disappeared from the record in millions of years, some are stable and will be preserved. There are also transuranic elements which are relatively stable, such as isotopes of plutonium and curium, whose half-lives are in the millions of years. Curium in particular doesn’t occur in any significant quantities on planets. Increased soil erosion also results in faster rates of sedimentation in rivers and estuaries, associated in part with the greater use of nitrogen fertilisers, and there are dead zones in the oceans as a result of nitrogen in this form allowing microörganism growth to outstrip the supply of oxygen. This can be seen to show up in the geological record, for instance at the biggest extinction of all at the end of the Permian, so it clearly does leave a mark. Incidentally, some scientists believe this is the main direct cause of mass extinctions. There are more rats and mice around than before, so an increase in the occurrence of particular fossils might be another sign. Technology is also able to create compounds more stable than those which arise without intervention, such as ones where chlorine and carbon are bonded, hexafluoroethane and sulphur hexafluoride, which will persist in the environment for hundreds of millions of years if not longer. Organic compounds formed biologically also have handedness, although in the case of amino acids these become mixtures over thousands of years, so the presence of steroids in mixtures of left- and right-handed forms, for example, would be a good sign. And of course there are plastics, although some of these are stimulating the evolution of bacteria which can digest them, or the proliferation of long-existing organisms who already could.
Ocean anoxia has occurred quite often in terms of the geological timescale of events. The aforementioned incident at the end of the Permian is one example. Others are seven such events, three of which were localised and minor, in the Cretaceous, and one in the Jurassic, often associated with an increase in carbon-13. There also seems to have been greater ocean sedimentation during these occurrences. There was also such an event in the Devonian, and particularly reminiscent of our time of deforestation, the loss of the Carboniferous rainforests is quite a 21st century event for so long ago.
But for some reason the Eocene has a cluster of such markers. The start of the Eocene 56 million years ago is officially marked by a sudden increase in the carbon and oxygen isotopes which in our time mark civilisation. For between one hundred and two hundred millennia, stable isotopes of carbon and oxygen other than the most common types both became more common. There was also global warming up to 7°C at the time. Vanadium, zinc, chromium and molybdenum all increased while this was going on, as did sedimentation in the oceans. Over the six million years after this, there were four more such events, although less dramatic, then forty million years ago there’s one more. The interesting thing about these is that the combination of unusual isotopes, global warming, apparent soil erosion and metals used in industrial processes all occur together, just as they are today.
One good argument against the existence of aliens is that we’re here at all. It seems that if a technology like ours arrived here in the æons of time over which life has existed on this planet, it would’ve caused serious damage to Earth’s ecosystem and perhaps wiped out all complex life, but there are no such incidents in our history. There’s also no species which isn’t related to all others, as might be expected if alien microbes had arrived on this planet later than the possibly first alien microbes to whom we might all be related. Hence we have to confront the rather disturbing prospect of a friendly habitable planet (at least to us) sitting here for countless millions of years without one single alien spacecraft landing on it, and that suggests there are no aliens, or at least no aliens yet. However, if there are recurring incidents of this kind in the geological record, the quandary becomes somewhat different, because instead of Earth never having been visited, the issue becomes the absence of alien microbes or other life forms on this planet. That issue, however, could be circumvented if it turns out these civilisations, which may of course never have happened, are actually from here, but the problem is then what animals they evolved from. The Palæocene is if anything even less promising than the later Eocene in this respect.
There are, then, three possibilities:
There has never been an advanced technological civilisation on this planet and the apparent technosignatures are just coincidences explained by other processes. This, being the most boring possibility, is the most plausible by far.
There has been at least one advanced technological civilisation which evolved from organisms already living here.
The planet has been visited and settled by advanced aliens.
There is a mixture of native and alien civilisations through our geological history.
The events of the Cretaceous may be more compatible with the idea of intelligent dinosaurs. The run up to the Cretaceous is many millions of years long, giving dinosaurs with human-like intelligence a lot of time to evolve, and some of the dinosaurs living today, such as parrots and crows, manage to achieve intelligence very similar to ours in spite of brains only weighing about thirty grammes compared to our fifteen hundred. However, the Eocene is more puzzling. The recent impact which had wiped out the larger dinosaurs did stimulate evolution, as mass extinctions often do, but it also caused the extinction of all larger animals, which are able to have larger brains, and it seems like it would’ve taken a long time for them to get that brain power back.
As a child, I made the following conjectures about past technological species here:
At the end of the Permian period, a species of mammaliforms evolved human-like intelligence and founded a civilisation which had such a devastating effect on the planet that it caused a mass extinction.
The coleurosaur (bipedal dinosaur with binocular vision and opposable thumbs – or at least I thought so at the time) Saurornithoides established a civilisation and wiped themselves out in a nuclear war, thereby explaining the iridium anomaly.
The ancestors of dolphins had their own technological culture about twenty-five million years ago, which is the point when their brains reached ours in size.
Homo erectus achieved an interstellar civilisation 800 000 years ago which only collapsed at the end of the last Ice Age.
I no longer believe in any of this, but I would want to modify the dinosaur one in particular, which I think is by far the most feasible, to incorporate Chicxulub, in that they could have moved an iridium-rich asteroid into orbit around this planet as a source of metals and accidentally crashed it into the Gulf of Mexico. The Cenozoic ones don’t line up with the events in the Eocene. Homo erectus evolved in the Pleistocene and the dolphins reached that stage in the late Oligocene, eight million years after the end of the Eocene.
The trouble with all of this is that it has a kind of quirky, eccentric sound to it and seems to be way outside of the scientific establishment. It’s particularly similar to tales of Atlantis and Von Däniken’s ancient astronauts, whichever version of the hypothesis you go with, apart from the first of course. On the other hand, why should we be the first, either in the whole Galaxy or on this planet? It seems arrogant to assume that, and on the whole we’re supposed to go with the Copernican Principle that there’s nothing special about us, and if there isn’t, maybe we aren’t the first, even on Earth. However, if there was a civilisation here during the Eocene, it seems unlikely it was from here, so maybe back then Earth was an outpost of the Pwqu Empire or something. After all, they left that giant mouth thing on that planet didn’t they?
Could it actually be Earth that was the cradle of interstellar civilisations at this time? There are reasons to suppose not. This would be the inverse of the possibility that aliens have visited this planet, because the chances are they would’ve left genetic traces as unrelated organisms. If the Galaxy had been filled by countless Earth colonies back in the Eocene, we’d be more likely to be living on one and find that there were two strains of life on it rather than the single one we observed. On the other hand, it is a bit odd that the first organisms on this planet seem to have been here during the Hadean, before Earth had even become even slightly habitable, so is it possible that all life in the Universe, or perhaps locally, is related and we’re looking at an extraterrestrial rather than a terrestrial common ancestor?
The kind of civilisation we’re looking for here is very much modelled after our own post-industrial, science-dominated culture, and it doesn’t follow that those would be the kind of societies which emerged millions of years ago. For all we know, and that phrase takes the proposition out of science because there’s no evidence but it’s still rational, civilisations may have evolved which were either very advanced in other ways or more cautious and reverent of Mother Nature. Maybe we don’t see evidence of civilisations like ours because we’re an anomaly, not because we are a community of sentient beings using technology but because of what we’ve done with it, or maybe other civilisations too went through an unsustainable industrial phase but ended up cleaning up after themselves. Nonetheless there is limited evidence for a civilisation in the Eocene, or perhaps a whole cycle of civilisations over millions of years, maybe collapsing due to unsustainability and environmental catastrophe before slowly making their way up the ladder, only to fall again millions of years later.
This may actually give us some hope. If the influence of past civilisations is so difficult for us to detect today that even the most recent ones, forty million years ago, managed to poo in its own bed so seriously that it wiped itself out and the planet recovered so well we can’t even tell it was there nowadays, it suggests that Earth has very powerful capacity to heal itself, and has done so before from the very onslaught we’re committing today. However, there’s no longer any trace of any putative civilisation remaining, which is also food for thought. We could, geologically speaking, be so thoroughly gone that nobody will ever even know we existed.
When should a story begin? If it’s a biography, common practice seems to be to recount the lives of the subject’s parents, although one might also talk about a more distant background. If I think about my own life history, it feels like a mistake to focus too much on background because it can easily drift into nationalism and racism. Many online discussions about genome analysis undertaken on White people seem to be embarrassed about recent Black ancestry and tend to be couched in terms of them being errors due to small amounts of data, which is really sad. On the other hand, it’s also possible for a White person in particular to appropriate swathes of Black or other Disneyfied ethnic identity for themselves for some kind of cringeworthy cool factor. Since my own ancestry is substantially Scottish, I could easily slot myself into tartanry. This kitschiness is very much to the fore and has been going on for two centuries now. Wikipedia describes it as “twee, distorted imagery based on ethnic stereotypes”. Two images of this in particular come to mind, both rather similar. One is of a tourist picking up a soft toy of a tartan mouse in Inverness and saying ,,Eine schottische Maus”, and the other is of a plethora of tartan Nessie plushies in a Loch Ness visitor’s centre gift shop. On the one hand, it’s quite embarrassing, but on the other one can understand the need to turn a somewhat honest penny in a remote location with few economic opportunities, and I imagine the same love-hate relationship with tourism I used to experience in Canterbury would be reproduced there. You need the tourists but they can be almost immediately tiresome.
In the case of human ancestry, we are all currently the product of at least two parents, who are in turn the product of two parents and so on back to a point where we appear to have more ancestors than the human population of the planet at the time. In fact you probably don’t even need to go back that far to experience that quandary, as people didn’t used to move around as much as many of us do nowadays. Many of my ancestors would probably have ended up marrying someone in the next village, or even the same village, and you can easily get back to the point where your family tree didn’t seem to have branches. This applied as much in West Afrika as it did in Argyll, although people did become displaced from both locations by events such as the Atlantic and Barbary Slave Trades, the Highland Clearances and the Famines. These mixtures have brought the common ancestors of all humans forward by millennia, such that it’s now estimated that our most recent common ancestor lived in the late Bronze Age, which when one considers how isolated certain groups are, such as in Papua or the Amazon, is quite counter-intuitive, but this reflects what has happened in recent centuries rather than further back.
As one ascends the global family tree, the generations become increasingly diagonal. Because most couples have at least two children survive to have children of their own, their age differences add up and start to skew the ages of people who, for us descendants, appear to be in the same generation. An extreme case of this might be a mother who has a child at twenty and another at forty, which is effectively a whole generation apart. In that case only two generations are needed for people in the same family to have a big enough age difference to be grandchild and grandparent, though not in practice of course. Even a year’s difference can achieve this within twenty generations. This also means that when one considers one’s ancestry, the range of possible dates of birth of unknown ancestors widens the further up you go. What would eventually happen, with perfect knowledge of the world’s population, is a family tree with multiple instances of the same individual in many places and different generations relative to oneself. The consequence of all this is that we are all part of the same human race.
This makes a lot of sense when considering evolution. It’s easy to imagine evolution as a sudden change in the population, and certainly point mutations do lead to this, but in fact what seems to make more sense is for a trait to begin in a certain individual and then spread across the species, and another trait to begin elsewhere and similarly spread, until you end up with a situation where either both traits, and of course many others, have spread throughout the population, leading to it having become a new species, or only some of them have, leading to either a ring species or the separation of the population into two or more such species. For solely sexually reproducing species, there cannot be a single founder of a new species, so for us, going way back into the past, it has always been a question of entire populations evolving together into new species.
A few days ago, I communicated poorly with someone by saying that our ancestors arose in North America, because they thought I meant hominids, the family including orang-utan, humans, gorillas, bonobos and chimpanzees, had arisen there. This is by no means the case of course, although there used to be a school of racialist anthropologists who believed in polygenesis: that the ancestors of surviving humans were already several different species. This would make humanity a grade rather than a clade – a group of organisms with the same kind of organisation in terms of anatomy and physiology which are, however, not descended from a common ancestor with those characteristics. These are seen a lot in biology. For instance, reptiles, when considered as a group of scaly air-breathing vertebrates whose bodies are at the same temperature as their surroundings when at rest, constitute a grade if some of the extinct “mammal-like reptiles” are included and birds excluded. Likewise, the mammal-like forms themselves consisted of several parallel lines developing the same kinds of characteristics but not from a common ancestor, and even hominids have done this. There used to be some confusion around a species of ape who had a number of particularly humanoid characteristics living in Europe before the first of our immediate ancestors got there, suggesting that we had evolved in Europe. The fact is that related species are wont to develop similar traits due to having similar genes and sometimes being in similar ecological niches.
But I actually meant omomyids. I think I’ve mentioned these before in this blog, so I won’t go into super depth on this, but back in the Eocene, 56-34 million years ago, primates were chiefly found in North America, and were of two main types: the adapids and the omomyids. Adapids were more lemur-like but less specialised, lacking the comb-like incisors and grooming claws found in many of their descendants. Both groups are themselves descended from the plesiadapiformes of the Palæocene, several million years previously, who looked like this:
Thus when I said “our ancestors”, I was referring to early primates, not hominids. It may be a little surprising that primates first appeared in North America, a continent from which non-human primates are almost absent (there are spider and howler monkeys in Mexico), but this distribution change is not unusual. Camels first evolved in North America around the same time as omomyids, but are now found on every continent except North America and Antarctica, although the Australian population is feral. Likewise, the earliest horses evolved in North America, spread to South America after the continents joined, then both American horse genera became extinct at the end of the last Ice Age, leaving them in Afro-Eurasia alone. This may, incidentally, have had huge consequences for human history as the domestication of the horse and the absence of exploitable beasts of burden in the Americas seems to have led to a major split in the types of culture which arose in those continents compared to Eurasia. There is in fact something of a pattern here, of particular mammalian clades evolving in North America, spreading elsewhere and then becoming extinct in the continent on which they originated. At the time, Earth looked roughly like this:
I chose a particular cut-off point here in a sense, because clearly forms ancestral to the primates would not initially have been native to North America, but the point was to contrast them with possible prehistoric Antarctic mammals. The Eocene was an extremely hot period, more so than any time during the reign of the dinosaurs, and consequently Antarctica was by no means snow-bound or ice-covered. The question was asked of whether there had ever been indigenous Antarcticans, to which the answer is not only “no”, but also that there haven’t even been indigenous Antarctican primates. One of the big divisions among mammaliforms is the Boreoeutheria versus the Gondwanatheria. As the name suggests, Boreotheria first evolved in the north, and share the primitive feature of males having scrota. They evolved about four million years before the Chicxulub Impactor arrived and were ancestral to the Euarchontoglires, a superorder including colugos, tupaias, rodents, lagomorphs and primates, as well as the Laurasiatheria, including fissipedal carnivores, seals, pangolins, odd- and even-toed ungulates, whales, hedgehogs and their kin, and bats. By contrast, the Gondwanatheria were native to the southern hemisphere, including Antarctica, may not even have been true mammals as such, and if they were, may have been a separate group of mammals and arguably the most successful and definitely the most durable, group, the multituberculates, mentioned before on here. Another southern group of mammals hard to place in relation to other placentals is the Xenarthra, who include sloths, armadillos and anteaters. There are also the Afrotheria, which include aardvarks, elephant shrews, some other shrew-like mammals, hyraxes, elephants, dugongs and manatees etc, and various extinct groups. Besides all these, there are of course the marsupials and monotremes (surviving egg-laying mammals). Hence Antarctica did seem to have marsupials and possibly some other mammals native to the southern hemisphere.
Back to primates. Omomyids and adapids had separate fates. It’s common for creationists to ridicule the established scientific paradigm by stating that the claim is that we evolved from monkeys. This is “not even wrong”, as the phrase has it. The earliest simians were the omomyids. They were somewhat tarsier-like, and although they began in North America, they spread into Eurasia. Tarsiers themselves are somewhat specialised, being nocturnal and having large eyes which are impossible to move by themselves, so their necks turn round almost all the way, which has led to them being perceived as spooky. They’re also kind of carnivorous, but like all simians (and no other primates) they need vitamin C in their diet, so I presume they must also eat fruit or some other good source. Omomyids generally had smaller eyes, were sometimes diurnal and had less flexible necks. Tarsiers have basically been the same for 45 million years now, so if you want a rough approximation of what our ancestors looked like, they wouldn’t be far off.
All monkeys, Old World and New, are descended from omomyids. The peculiar claim that apes are not monkeys is a bit dubious because cladism insists on creating groups consisting of all descendants of a common ancestor, so in that sense we are still monkeys. We’re also apes, and apes are monkeys. This is a little awkward, because of the sloppy use of terminology that tends to call non-human apes monkeys. Technically that’s correct, but they’re tailless monkeys with torsos wider than they are thick. Another issue is with the racist use of the words to imply inferiority, meaning that although biologically we’re monkeys and of course also apes, it may also have offensive connotations. One answer might be to reclaim these terms, but as the world’s Whitest woman I can’t really go around saying I’m doing that for their sake, any more than I can spell “Afrika” with a C in spite of the fact that I have my doubts about the rationale of spelling it with a K.
The question arises of what happened between the omomyids and the emergence of hominids. This would be the Oligocene. In the Miocene it’s well-established that there was a great variety of different kinds of apes and it’s therefore difficult to trace human lineage through that thicket of similar forms. Before that, however, was the Oligocene. A significant animal from this time is Ægyptopithecus zeuxis:
This primate lived before the ancestors of Old World monkeys and the ancestors of apes separated, around thirty million years ago. Before this, there was an Old World primate called Oligopithecus who was more like a marmoset or tamarin than today’s Old World monkeys, and this raises the issue of how they got there. The split occurred about forty million years ago, which is in the Eocene, and their arrival in South America is controversial. Although there were primates in North America at the time, which would’ve meant convergent evolution with Old World monkeys to some extent, it’s more likely that they travelled over the Atlantic on rafts of vegetation, bearing in mind that at that time the ocean was narrower and the rainforests in Afrika still existed further north. Hence sadly, monkeys did not evolve twice. If they had, it would make the idea of humanoid aliens slightly more plausible. The New World monkeys themselves began to diverge from each other around 27 million years ago and now comprise five families. Although the smaller marmosets might be thought of as having evolved from larger monkeys to occupy the vacant prosimian niches in the Amazon, in the light of the likes of Oligopithecus it looks more like they were the more primitive forms and the reason they’re more prosimian in size is that they’re genetically closer to them, although this is just my guess. It does make sense that it would’ve been easier for smaller primates to survive being swept across the ocean, but there were other primates which initially made a living there but soon died out, such as the Afro-Arabian-Asian parapithecoids, who were very monkey-like.
Primates used to be a lot more widespread than they are today. There were European native primates such as Dryopithecines, who could’ve been closer to Afrikan apes, orangutan or perhaps equally related to both. They’re quite neat, as they’re apes who dominated Europe before humans reached here. They were roughly bonobo-sized and ate fruits and leaves. Later on, they may have built up fat reserves in the summer to tide themselves through the winter.
As for our immediate hominin ancestors, I should hold my hands up here and confess to being an adherent of the aquatic ape hypothesis. The standard narrative is that some apes became more humanoid during the drying period of the late Miocene and the Pliocene, being forced to survive on the Afrikan savannah. This is not what I believe. In order to explain why this could not have happened, I need to talk about endogenous retroviruses. These are stretches of genomes which used to be viruses, which have transcribed their genomes into those of other organisms. At some point in the Pliocene, baboons started to shed a virus of this type which infected all other primates in Afrika. No Asian or South American primates have this area of genome, and all Afrikan primates do have it. Humans do not have it, although up to eight percent of our genomes are made up of retroviral code. This is from before the appearance of genus Homo. It appears to support an Asian origin for our ancestors, but it’s equally compatible with them having been isolated on an island off the Afrikan coast. The oldest stone tools are found in Ethiopia and seem to have spread south. There are also a number of adaptations in humans which suggest we spent a lot of time in the water, such as:
Near-hairlessness.
Insulation from fat deposits, including floating breasts more accessible to young in the water, along with long scalp hair affording protection from the Sun and a handhold for babies.
A hymen, protecting the reproductive system from sand.
The presence of a diving reflex, where metabolism and heart rate slow when immersed in water.
Breath control.
Face to face lovemaking, found mainly in marine mammals.
Downward-facing nostrils.
Erect bipedalism.
I’m not being thorough here. This is just a selection of adaptations which suggest we had an aquatic phase. However, this doesn’t mean we lived in the water like dolphins. It’s more like we lived on the beach and escaped into the water from potential predators, kind of like we were semi-mermaids. It’s also possible that elephants went through a similar phase, as they still have a lot to do with water. Moreover, early stone tools were made from pebbles, as found on beaches. Proboscis monkeys also have similar adaptations, such as their noses, and spend some time in water.
I think that’s all I really want to say today. It’s a bit spotty, but I’ve tried to highlight some of the less well-known bits of the history of primates. There’s a lot of other stuff, such as the orang-utan relatives who lived in the Himalayas and the recently extinct northern Chinese gibbon species, but this will probably do for now.
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):
. . . 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.
A Box Of Chocolates 