Evolutionary debunking arguments and the proximate/ultimate distinction

Many philosophers believe that natural selection explanations debunk our moral beliefs or would do so if moral realism were true, relying on the assumption that explanations of this kind show that moral facts play no role in explaining human moral beliefs. Here I argue that this assumption rests on a confusion of proximate and ultimate explanatory factors. Insofar as evolutionary debunking arguments hinge on the assumption that moral facts play no role in explaining human moral beliefs, these arguments fall short.