According to Haidt,[28] the belief that morality is not innate was one of the few theoretical commitments uniting many of the prominent psychologists studying morality in the twentieth century (with some exceptions[57][58]). A substantial amount of research in recent decades has focused on the evolutionary origins of various aspects of morality.[59][60][61][62]
In Unto Others: the Evolution and Psychology of Unselfish Behavior (1998), Elliott Sober and David Sloan Wilson demonstrated that diverse moralities could evolve through group selection.[63] In particular, they dismantled the idea that natural selection will favor a homogeneous population in which all creatures care only about their own personal welfare and/or behave only in ways which advance their own personal reproduction.[63]
Tim Dean has advanced the more general claim that moral diversity would evolve through frequency-dependent selection because each moral approach is vulnerable to a different set of situations which threatened our ancestors (see also Pragmatic ethics § Moral ecology)