Abstract

Evolutionary psychology is found deficient in its conception of both how the brain was rewired during hominin evolution and how neurological systems evolve. The modular structure of the brain was in place many epochs before the Pleistocene, with evolution on the hominin line revolving primarily around directional selection on the tail ends of trait distributions and producing rather diffuse and complex sub-assemblages across large expanses of the neocortex and subcortex rather than discrete, functional modules. Most of the behavioral traits characteristic of humans already existed as bioprogrammers in the mammalian and/or primate brain, but were insufficient to increase sociality and group bonding without some enhancement by directional selection on the neurological systems responsible for these behaviors and, more importantly, on the subcortical emotional systems that became the replacement for the typical bioprogrammers for group formation among mammals that had been lost to great apes during their evolution in the arboreal habitat. By engaging in comparative anatomy, using present-day brains of the great apes as a distant mirror on the ancestors of extant apes and humans, differences in the wiring of ape and human brains provide a much better picture of how the hominin and then human brain evolved during the Pleistocene.