Why you have one trait rather than another: The failure of the explanatory-chain strategy

In The Nature of Selection (1984), Sober argued that natural selection is in principle powerless to explain why any individual organism has the traits it does rather than the very same individual having different traits. A debate ensued, in which critics have argued against Sober by laying explanations end-to-end, to form a chain of explanation that begins with selection and passes through one or more intermediate events before reaching the target explanandum. I argue that Sober’s critics misunderstand how contrastive explananda (why p rather than q) behave in such explanatory chains, and that this strategy has so far failed.