Sexual differentiation in humans Sexual differentiation in humans Sexual differentiation in humans is the process of development of sex differences in humans. It is defined as the development of phenotypic structures consequent to the action of hormones produced following gonadal determination. Sexual differentiation includes development of different genitalia and the internal genital tracts, breasts, body hair, and plays a role in gender identification. The development of sexual differences begins with the XY sex-determination system that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between male and female humans from an undifferentiated zygote. Females have two X
Neoteny in humans neotenic changes may have disparate roots. Some may have been brought about by sexual selection in human evolution. In turn, they may have permitted the development of human capacities such as emotional communication. However, humans also have relatively large noses and long legs, both peramorphic (not neotenic) traits, though said peramorphic traits that separate modern humans from extant chimpanzees were present in Homo erectus to an even higher degree than in Homo sapiens, keeping general neoteny valid for the erectus to sapiens transition although there were perimorphic changes separating erectus from even earlier hominins such as Australopithecus. Many prominent evolutionary