In the LRB, Simon Blackburn, Jerry Coyne, Philip Kitcher, Tim Lewens, Steven Rose pen a joint response to Jerry Fodor’s response to letters on the issue:
Jerry Fodor persists with two provocative claims: first, that natural selection explanations are incoherent; second, that there is some alternative explanation for adaptive phenomena such as camouflage or beak shape (Letters, 29 November).
To show the incoherence of anything, you have to address it in the form in which its professional expositors deploy it. In large numbers of articles and books, published from 1859 to the present, evolutionary biologists use the following style of explanation. A characteristic of an organism (the colour of an animal’s coat, say) is as it is because of a historical process. In some ancestral population there was a variant type that differed from the rest in ways that enhanced reproductive success. (White polar bears, for example, more camouflaged than their brown confrères, were better at sneaking up on seals, were better fed and left more offspring.) If the variant has a genetic basis, its frequency increases in the next generation.
Is this incoherent? Nothing Fodor says bears on that question.
Fodor:
[T]hey offer some potted polar bear history: ‘White polar bears . . . more camouflaged than their brown confrères, were better at sneaking up on seals, were better fed and left more offspring.’ I don’t know whether this story is true (neither, I imagine, do they), but let’s suppose it is. They ask, rhetorically, whether I think it’s incoherent. Well, of course I don’t, but that’s because they’ve somehow left out the Darwin bit. To get it back in, you have to add that the white bears were selected ‘because of’ their improved camouflage, and that the white bears were ‘selected for’ their improved camouflage: i.e. that the improved camouflage ‘explains’ why the white bears survived and flourished. But now we get the incoherence back too. What Darwin failed to notice (and what paradigm adaptationists continue to fail to notice) is that the theory of natural selection entails none of these. In fact, the theory of natural selection leaves it wide open what (if anything) the white bears were selected for.