Within-species individual differences

The process of natural selection results in the non-random reduction of the genetic variation within a population via the subtraction of alleles that produce reproductively unsuccessful phenotypes from subsequent generations. As such, variation within a species is parochially viewed as a figurative fuel that is 'consumed' by the forces of evolution in the production of creatures more adapted to the survival and reproductive demands of their environments (Darwin, 1859; Sela and Shackelford, 2015). While this summary is true, in the strictest sense, it also fosters one of the central oversimplifications employed by theorists investigating possible adaptations: the assumption that the sole outputs of evolution by natural selection are features so unambiguously favored by their selective advantages as to render them species-typical (Tooby and Cosmides, 2005). This chapter reviews the main ways in which the paradigm of evolutionary psychology can address, interface with, and enhance the study of individual differences, most notably in areas of personality and cognitive ability.