A Proof of Man’s Apish Origins

A Proof of Man’s Apish Origins

For the purposes of this proof, I will assume that general Creationism is false: animals evolved over billions of years by mutation and natural selection. The question at issue is how to establish that the species Homo sapiens evolved from an apelike ancestor.[1] It is not that I think this has not already been proved (it has); I am interested in exploring the epistemology of the question—how it can be known, what kind of justification might be given for it. I am interested in the epistemic status of the claim—the kind of reasoning that might lead to it (so my aims are primarily philosophical). What is the logical structure of the question’s answer? So, we begin by assuming that other existing animals all evolved from distinct species from which they are descended by natural selection. Then the human species might follow suit or it might not. If it doesn’t, it would be anomalous—perhaps separately created from scratch by God or some powerful alien. That is massively implausible for many reasons—we would need such superior intelligences to exist and for them to have some very strange designs. Thus, we may assume that man did evolve from an earlier distinct species: our species fits with the rest of nature as to its origins, on pain of denying the uniformity of the biological world. The question, then, is which earlier species—and here things get interesting. For there are indefinitely many species from which man could (logically) have evolved. All we know so far is that man descends from some earlier species, but why not crabs or dogs or reptiles? What if someone maintained that we are ignorant of what type of species gave rise to the human species, though some type certainly did? The answer to this skeptical possibility is obvious and immediate: we need to identify the existing species most similar to us—then we can reasonably infer that we and they share a common ancestor. Clearly, crabs, dogs, and reptiles are not the most similar to us—apes are. We look and behave in very similar ways—no species more so. Therefore, we evolved from apelike creatures: that is the only rational conclusion we can draw. We know what kind of species we evolved from—whatever the most similar animals to us evolved from. We know that we and contemporary apes share a close common ancestor. If Neandertals still existed, we could make the same inference with respect to them. Thus, we know we had some distinct species as ancestor, by the uniformity of biological nature; and we also know that that species had to be ape-like, because apes are most like us and so share our ancestry. By the same argument, apes could know they had a human-like ancestor, because they are similar to us and share their ancestry with us. Of course, we both no doubt differ from this common ancestor quite a bit, but it is still our common ancestor and thus like both of us. Humans are apelike and apes are humanlike—neither of us is crablike or doglike or reptilelike. Put simply, we descended from bygone apes, as apes also did (symmetrically, they could say they descended from humanlike creatures not crabs—that life-form). More cautiously, we share a relatively recent apish ancestor. Our ancestry went through an apish stage, as the ancestors of apes went through a humanish stage (though not humans in their contemporary form). We have proved this proposition without relying on genetic evidence or the fossil record or microanatomy or actual observation of evolutionary lineages (not that there is anything wrong with these kind of evidence). The proof is pretty commonsensical and a priori, requiring no elaborate scientific discoveries; it is intelligible to the scientifically illiterate person. It establishes an important and non-obvious proposition, one well worth knowing.

I now want to make a stronger claim, namely that it is actually quite easy to establish a general Darwinian position, at least in principle. That is, we can show that all animals evolved by mutation and natural selection from a fairly exiguous evidential basis. This may sound unlikely, but consider: if we could observe a single instance of evolution by natural selection, we would have shown that all animals evolved this way. Suppose we observed a mouse evolving from a non-mouse by natural selection (or even a fly): wouldn’t that show that all animals came into existence this way because otherwise nature would not be uniform? I don’t mean to suggest I have solved the problem of induction; I mean only that it would be sound science to generalize the particular case. If it can happen in this way, and our sample case is not special in any respect, then it must happen in this way. It’s like inferring general gravitation from observation of specific cases. If we observed something else happening in the production of a new species, we could infer that too as a general proposition; you don’t need to examine every case individually. So, we could establish the truth of Darwinism by arranging an experiment in which a new species observably evolves by natural selection; it might take a while but it could be done. We would then know that Creationism is false (of course, we already know this on other grounds). We could then conjoin this result to the above argument to show that man evolved from apish creatures. There is really not that much that needs to be done in order to establish the general Darwinian position; it isn’t some speculative unverifiable leap in the dark, and wasn’t so in Darwin’s time (of course, he had a lot of opposition to contend with). As commonsense science, his “theory” is overwhelmingly plausible—not say inescapable. Evolutionary biology is easy! It’s epistemologically a lot easier than astronomy or physics or chemistry or psychology. You just need to get the junk out of the way and the theory becomes clearly and obviously true. It isn’t that we are dealing with incredibly remote history that we can only speculate about; we are dealing with obvious observable facts (in principle anyway). Indeed, once we establish that intraspecies variation exists, it is a very short step to reach the conclusion that species evolve by natural selection (this was the main point of The Origin of Species). You don’t need much more empirical information, since it is relatively a priori to deduce that there is no principled difference between intraspecies variation and speciation. The whole thing is staring us in the face, with only tradition and religion blocking the view. Clearly, speciation is intraspecies variation writ large; clearly, if one species evolved from another, they all did; and clearly, man evolved from apes, they being the obvious candidate for man’s species origins. Clearly, too, the whole process stretches back a long way, because this kind of change doesn’t happen overnight. All the rest is icing on the cake. Darwinian science is really commonsense science. Of course, we evolved from apes; and of course, all animals exist by natural selection extending over geological time. Nothing else makes any sense. This is not to belittle Darwin’s achievement; it is just to put on record the fact that it enjoys firm epistemic foundations and is in no way contradictory to common sense. Dog breeding by itself is virtually sufficient to establish the whole thing, as Darwin himself in effect recognized. If artificial selection can produce very different breeds, natural selection can do likewise. The breeds have their origin in intermediate breeds, and similarly for species. And it couldn’t be that one breed of dog alone (say, the golden retriever) owes its origin to some other supernatural mechanism. The essential points are all contained in dog breeding: the origin of species, the descent of man, the length of evolutionary time, the differentiating action of natural selection. We just need to perform an elementary mutatis mutandis.[2]

[1] This paper was prompted by reading chapter six of Darwin’s The Descent of Man (1871) in which many details are adduced to defend the thesis of our ape ancestry. Of course, that thesis has been elaborately defended ever since, and is now accepted science.

[2] It has often been remarked that the idea of evolution by natural selection is simple and available to any intelligent student of nature—so why did it take so long before Darwin and Wallace formulated it? Similarly, the practice of breeding (artificial selection) had been a commonplace long before Darwin realized its implications—why was this not recognized before? In effect, nature can breed for success as well as human breeders, exploiting the power of genetics to shape organisms; instead of “natural selection” Darwin could have said “natural breeding” (both verbs carry connotations of intentional intelligence). Animals naturally vary and all we or nature have to do is perpetuate some variations and eliminate others: that is the heart of the matter. Really, it should have been obvious how species came to exist—and the theory can be stated in a short paragraph. It isn’t some arcane esoteric piece of genius-level science (like the big bang and quantum theory).