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:

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.



