Phenotypic Plasticity, CYP19A1 Pleiotropy, and Maladaptive Selection in Developmental Disorders

The contribution of evolutionary psychology to the study ofdevelopment and psychopathology depends on adherence to the principles of evolutionarybiology. The human brain evolved because selection favored neither size nor complexitybut instead the phenotypic plasticity supporting cognitive flexibility. Cellproliferation, migration, elongation, synaptogenesis, synaptic pruning, apoptosis, andmyelination occur at varying rates during asynchronous phases of development throughoutthe brain. Developmentally sensitive periods result from phenotypic plasticity and arevital for adaptation to the environment. The biological systems surrounding the CYP19A1gene provide mechanisms for neuroprotection and targeted neuronal debridement inresponse to environmental stress, uniting selection with developmental biology. Updatesto Dunbar’s original hypothesis with current primatological data, inclusion of totalbrain mass, and the introduction of CYP19A1 orthology from nine primate species yields alinear regression, R 2 = .994, adjusted R 2 = .989, F(3, 5) = 143.758, p <.001