Embryos and Ancestors

Abstract

Evolutionary developmental biology, or Evo Devo, examines how developmental mechanisms affect evolutionary change. Heterochrony refers to genetic-based differences in developmental timing. One important type of heterochrony for humans is neoteny, which refers to the retention of juvenile traits into later development. Humans are a neotenous species, as seen in infants’ features of “babyness,” which promote attention and caring from adults, extending the primate prenatal brain growth rate well past birth, and a reduction of reactive aggression relative to great apes, which facilitated increased cooperation among group members. Homo sapiens extended the time it takes to reach adulthood by inventing new two life stages—childhood and adolescence. The social and cognitive abilities of Homo sapiens’ youth may be well suited to the childhood and adolescent stages and to the attainment of skills necessary for developing into functional adults.