Violence Decline Too Fast to Be Genetic

Declines in violence occur on timescales far too short for Darwinian natural selection—Germany shifted from the world's most militaristic to its most pacifist culture in roughly a generation, and the American homicide rate halved in eight years—so we need not invoke any genetic change to explain historical reductions in violence, even if a slow genetic contribution (as Gregory Clark speculated) cannot be entirely ruled out.