According to most Evolutionary Psychologists, human moral attitudes are rooted in cognitive modules that evolved in the Stone Age to solve problems of social interaction. A crucial component of their view is that such cognitive modules remain unchanged since the Stone Age, and I question that here. I appeal to evolutionary rollback, the phenomenon where an organ becomes non-functional and eventually atrophies or disappears-e.g. cave-dwelling fish losing their eyes. I argue that even if cognitive modules evolved in the Stone Age to solve problems of social interaction, conditions since then have favoured rollback of those modules. This is because there are institutions that solve those problems-e.g. legal systems. Moreover, evidence suggests that where external resources are available to perform cognitive tasks, humans often use them instead of internal ones. In arguing that Stone Age cognitive modules are unchanged, Evolutionary Psychologists say that evolutionary change is necessarily slow, and that there is high genetic similarity between human populations worldwide. I counter-argue that what is necessarily slow is the building-up of complex mechanisms. Undoing this can be much quicker. Moreover, rollback of cognitive mechanisms need not require any genetic change. Finally, I argue that cross-cultural similarity in some trait need not be rooted in genetic similarity. This is not intended as decisive evidence that rollback has occurred. To finish, I suggest ways we might decide whether moral attitudes are likely to be rooted in unchanged Stone Age modules, given that I have argued that cross-cultural similarity is not enough.
