Impact of the human egalitarian syndrome on darwinian selection mechanics.

With nothing more than kin selection and reciprocal altruism theories to work with, the selection basis of human degrees of altruism and cooperation is often difficult to explain. However, during our prehistoric foraging phase, a highly stable egalitarian syndrome arose that had profound effects on Darwinian selection mechanics. The band's insistence on egalitarianism seriously damped male status rivalry and thereby reduced the intensity of selection within the group by reducing phenotypic variation at that level, while powerful social pressure to make decisions consensual at the band level had a similar effect. Consensual decisions also had another effect: they increased variation between groups because entire bands enacted their subsistence strategies collectively and the strategies varied between bands. By reducing the intensity of individual selection and boosting group effects, these behaviors provided a unique opportunity for altruistic genes to be established and maintained. In addition, the egalitarian custom of socially isolating or actively punishing lazy or cheating noncooperators reduced the free-rider problem. In combination, these phenotypic effects facilitated selection of altruistic genes in spite of some limited free riding. This selection scenario remained in place for thousands of generations, and the result was a shift in the balance of power between individual and group selection in favor of group effects. This new balance today is reflected in an ambivalent human nature that exhibits substantial altruism in addition to selfishness and nepotism.