It is very difficult to get through a degree in biology without ending up believing Darwin’s account of the history of life. That is because the evidence for it seems to be everywhere. It’s not a single spectacular proof or a brilliant theoretical argument — it’s a cumulation of a thousand little things that seem to point to the theory. One day, you’re learning why frogs evolved hearts with two atria instead of one; the next day, you’re learning why the beaks of birds on one island differ from the beaks of birds on another. Evolution just explains so much about the world around us.
In fact, it begins to feel as if it explains too much. You begin to wonder… what couldn’t evolution explain? Is there any hypothetical observation that wouldn’t be gamely incorporated into the theory? And if not… is that really a strength of the theory?
According to mainstream philosophy of science, the answer is no. If a theory seems like it could explain any conceivable phenomenon, this may be an indication that it is a circular argument which is designed to be irrefutable.
A Disquieting Pattern
Karl Popper, one of the most influential philosophers of science of the 20th century, is generally credited with this insight. For Popper, what a theory could explain was not so important as what it couldn’t explain. In his classic lecture “Science: Conjectures and Refutations,” Popper asked his readers to consider the psychological theory of Alfred Adler, which taught that much of human behavior could be explained by subconscious feelings of inferiority called an “inferiority complex.” The problem for Popper was not that the theory failed to explain observations about human behavior. Rather, it seemed that there was nothing that couldn’t be explained by Alder’s theory. If a man pushed a child off a bridge, it was because the man felt inferior and needed to prove to himself that he dared to do it. If another man jumped in the water to save that child, well, he did so because he needed to overcome his sense of inferiority and prove that he dared to save him.
Popper saw this disquieting pattern in several contemporary “sciences.” He wrote:
I found that those of my friends who were admirers of Marx, Freud, and Adler, were impressed by a number of points common to these theories, and especially by their apparent explanatory power. These theories appeared to explain practically everything that happened within the fields to which they referred. The study of any of them seemed to have the effect of an intellectual conversion or revelation, opening your eyes to a new truth hidden from those not yet initiated. Once your eyes were thus opened you saw confirming instances everywhere: the world was full of verifications of the theory. Whatever happened always confirmed it.
Things That Make Sense in the Light of Evolution
It’s difficult to read Popper’s comments without Theodore Dobzhansky’s famous statement springing to mind: “Nothing in biology makes sense except in the light of evolution.” That may be so, but if you’ve listened to evolutionary biologists long enough, it’s hard to imagine anything that wouldn’t make sense in the light of evolution. Darwin’s theory can explain anything. That’s what makes it so powerful.
For instance:
- If a trait is adaptive, then of course this is evidence of Darwinian evolution. (After all, isn’t “survival of the fittest” a key pillar of the theory?) But if a trait is apparently not adaptive, then this is evidence for another pillar of Darwinism — random, unguided variation. (Why would an “intelligent designer” make something imperfect?)
- If we can observe a slow, incremental diversification of species in the fossil record, then of course this confirms Darwin’s hypothesis, because Darwin predicted that evolutionary change must be gradual. But if some groups of species seem to have diversified very rapidly, then, well, this is just evidence that evolution is faster and more powerful than had been supposed (as evolution biologist Andreas Wagner recently wrote)1.
- Similarly, Nobel laureate geneticist François Jacob predicted that wholly original “de novo” genes could never be produced by evolution, because the odds of that happening were “practically zero.” When it turned out that de novo genes do in fact exist, we were told by evolutionary biologists that this merely “proves that evolution can create complex features of a genome from scratch,” and that de novo genes “teach us that we may not give evolution’s creative powers enough credit.”2
- Prior to the results of the ENCODE project in 2012, we were told that the prevalence of apparently useless “junk DNA” in genomes was evidence of Darwinian processes at work. Afterwards, when it was revealed that much of the junk was probably not actually junk, we were told that this did not run counter to the Darwinian hypothesis at all. “Quite the contrary,” Richard Dawkins said, “it’s exactly what a Darwinist would hope for, is to find usefulness in the living world…”
- Traditionally, similar traits shared by different species are called “homologous” and are considered powerful evidence for the common ancestry. But if it happens to be obvious that the species in question could not possibly share a common ancestor (due to differences in geography, chronology, or the contrary evidence of better-established phylogenies), then similarities are no longer evidence of common ancestry but rather evidence of “convergent evolution.”
- If an organism exists at all, this is evidence that it evolved — because how else would it have come to be?
So where are the things that evolution can’t explain? The more you think about it, the harder it is to imagine a discovery that would be declared evidence against Darwinism. The idea of such a thing being even tentatively suggested in a journal like Nature is laughable. It would never happen, no matter what was discovered. Every possible phenomenon can be explained by Darwinian evolution, and therefore, everything is evidence for Darwinian evolution.
All for One, and One for All
Someone might object that scientists would be foolish to declare any new discovery “evidence against Darwinism,” because any hypothetical new discovery must be interpreted in light of the vast body of evidence for Darwin’s theory which already exists.
As it happens, Karl Popper pinpointed this very attitude as the reason non-scientific ideologies were so difficult to challenge. Because every piece of evidence must be interpreted in light of the imagined whole — that is, in such a way as to not contradict the theory — you could never accumulate a critical mass of evidence against the whole. This paradigm-reinforcing effect was first brought to Popper’s attention by a conversation he had with Alfred Alder himself. As a young man, Popper had participated in Adler’s social work, and he happened to come across a case of child psychology that did not seem at all in line with Adler’s theory. Yet when he mentioned it to Adler, the psychologist had no trouble explaining how the child’s case actually was explained by an inferiority complex. Unconvinced, Popper asked him how he could be sure. Adler replied: “Because of my thousandfold experience.”
Popper’s (somewhat cheeky) response was, “And now I suppose you have thousand-and-one-fold experience.”
A Floating Castle
“What I had in mind,” Popper wrote, “was that his previous observations may not have been much sounder than this new one; that each in its turn had been interpreted in light of ‘previous experience,’ and at the same time counted as additional confirmation.” It was a floating castle, with no real foundation.
You can observe the beginnings of this kind of circular argument in Darwin’s own writing. “The great break in the organic chain between man and his nearest allies, which cannot be bridged over by any extinct or living species,” he wrote, “has often been advanced as a grave objection to the belief that man is descended from some lower form; but this objection will not appear of much weight to those who, convinced by general reasons, believe in the general principle of evolution.”3
In the decades after Darwin, the problem has only gotten worse. The challenges continue to pile up, but the pile never seems to get any bigger because each piece of contrary evidence is dismissed or reinterpreted for “general reasons.” And so the paradigm is irrefutable. But irrefutable belief systems that can explain every possible piece of evidence are not “science.” They have a different name. And unfortunately, they are only convincing from the inside.
Notes
- Andreas Wagner (2023). Sleeping Beauties: The Mystery of Dormant Innovations in Nature and Culture, pages 27-28, 131. Oneworld Publications.
- Ibid, 131-133.
- Darwin, Charles (1871). The Descent of Man, pages 200-201. Murray.