This dissertation examines the implications of seeing moral beliefs and moral behaviour as evolutionary adaptations. In particular, it discusses whether or not an evolutionary explanation of human moral behaviour should lead us to reject the idea of objective moral facts. I agree with Michael Ruse that moral behaviour can be explained in naturalistic terms. However Ruse believes that this should not lead us to reject some forms of moral realism, as morality is a shared adaptation. My arguments against this are (...) twofold. Firstly I believe that if morality is a product of natural forces then there will be variation between individuals’ moral sense; which should give us cause to reject all forms of moral realism. My second argument is that Ruse is internally inconsistent, and he is trying to ‘sneak’ moral facts back into the picture, having previously rejected them. (shrink)