Group selection in the Upper Palaeolithic

Using criteria of relative plausibility, it is possible to make a case for significant group selection over the 100,000 years that Anatomically Modern Humans have been both moral and egalitarian. Our nomadic forebears surely lived in egalitarian communities that levelled social differences and moralistically curbed free-riding behaviour, and this egalitarian syndrome would have had profound effects on levels of selection. First, it reduced phenotypic variation at the within-group level. Second, it increased phenotypic variation at the between-group level. Third, and crucially, moral sanctioning also permitted groups to sharply curtail free-riding tendencies at the level of phenotype. The result was group selection strong enough to support altruistic genes, and a human nature that was set up for social ambivalence: that nature was mainly selfish and strongly nepotistic, but it was at least modestly and socially significantly altruistic. The effects on human social and moral life were pervasive, both in hunting bands and in more recent manifestations of human society.