Coyne on Natural Selection

Jerry Coyne offers some further thoughts on the Richard Lewontin essay I discussed in yesterday's post. Specifically, he addresses the question of why natural selection deserver pride of place among evolutionary mechanisms. He writes:

First of all, yes, it's true that the evidence for natural selection as the cause of most evolutionary change in the past is not as strong as the evidence that evolutionary change occurred. It cannot be otherwise. We can see evolution happening in the fossil record, but it is infinitely harder to parse out the causes of that change. We weren't around when it occurred, so we must rely on inference. This difficulty is one reason why it took biologists much longer to accept natural selection than to accept evolution. But to say that the evidence for selection is weaker than for evolution does not mean that the evidence for natural selection is weak, a conclusion I fear that creationists will extract from Lewontin's comment.

I think you could quibble over whether we actually “see” evolution in the fossil record (it's going to depend on how you define “evolution”), but Coyne's point is well-taken. He backs it up further with six good reasons for accepting natural selection as an especially important evolutionary mechanism.

I also liked this:

What about my supposed double standard about accepting natural selection for many traits but being skeptical when it comes to evolutionary psychology? This is a reasonable tactic for one important reason: we have many more alternative theories for the appearance of human behavioral traits than we do for morphological adaptations in other species. How many alternative theories do we have for the appearance of flippers in proto-whales, or for the movement of their nasal passages to the top of their heads? In contrast, there are many alternative theories for the appearance of traits like human rape, depression, music, art, religion, etc. Blowholes aren't likely to be spandrels; the appearance of music and poetry might well be. Humans have culture and rationality to a degree possessed by no other animal, and can learn many things not permitted in species having smaller (or no) brains. That's why we need to be more cautious about imputing selection to human behaviors than to blowholes.

Well said! I would add that the price for being wrong is greater when studying human psychology than it is when studying the blowholes of whales (a point also made by philosopher Phillip Kitcher about sociobiology). An erroneous understanding of blowhole origins is not likely to lead to bad public policy. An erroneous understanding of human nature, on the other hand, could do precisely that.

Natural selection gets it from both directions. On the one hand people point to various complex structures and assert that there is no way to explain something so magnificent by reference to gradual accretion. But when a scientist then comes up with a plausible, step-by-step account for how the structure could have formed, suddenly the criticism is that you can come up with a story to explain anything.

If you have ever attended a creationist conference, there is a good chance that you have even heard both of those arguments made in the same talk.