Adaptive genetic variation and human evolutionary psychology

Abstract

Phenotypic differences between individuals can be adaptive (the product of natural selection) or nonadaptive. Adaptive individual differences can be caused by underlying genetic differences or by mechanisms of phenotypic plasticity that allow single genotypes to achieve multiple forms. Many examples of adaptive individual differences have been documented in nonhuman species and these differences tend to be caused by a mixture of genetic polymorphisms and phenotypic plasticity.

Human evolutionary psychologists appreciate the adaptive nature of individual differences at the phenotypic level but they tend to overemphasize the importance of phenotypic plasticity as the proximate cause. I criticize this position, focusing on the work of J. Tooby and L. Cosmides. I briefly review the literature on nonhumans, species, review and criticize arguments against adaptive genetic variation in humans, and present a model that shows how a combination of genetic polymorphism and phenotypic plasticity might be favored by natural selection in humans and other species.