Open Access Kent State (OAKS)

Multiple selective pressures maintain and increase heritable behavioral variability among individuals across both developmental and evolutionary time: (1) directional social selection favors convergent traits, promoting mutually beneficial cooperative interactions; (2) disruptive social selection favors divergent traits, providing release from within-species competition; (3) genetic diversification responds adaptively to the stochastic (random) characteristics of environmental hazards such as uncontrollable morbidity (disease) and mortality (death); (4) developmental plasticity epigenetically directs development adaptively along different alternative pathways, modifying permanent and stable behavioral dispositions to suit long-term contingencies of survival and reproduction; and (5) behavioral flexibility deploys rapid and reversible short-term adaptive behavioral responses to transient situations.

Evolutionary psychology is an important meta-theoretical paradigm for understanding universal and sex-differentiated adaptations. Despite this, it remains somewhat ignored within the mainstream study of individual differences. We outline some of the evolutionary approaches that lend to a fuller understanding of individual differences related to personality psychology. This chapter is presented in four main sections: (1) a brief summary of trait-based approaches that have been used to understand human personality, (2) an introduction to some of the evolutionary principles important to understanding behavior, (3) an explication of the function of individual differences within populations and the evolutionary mechanisms that produce such variation, and (4) a review of contemporary evolutionary models of individual differences with particular focus on personality traits.