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 lower second and third molars. Populations with a history of dairy farming have evolved to be lactose tolerant in adulthood, whereas other populations generally lose the ability to break down lactose as they grow into adults. Down syndrome neotenizes the brain and body. The syndrome is characterized by decelerated maturation (neoteny), incomplete morphogenesis (vestigia) and atavisms. Neoteny in humans Neoteny in humans is the retention of juvenile features well into adulthood. This trend is greatly amplified in humans especially when compared to non-human primates. Adult humans more closely resemble the infants of gorillas and chimpanzees than the adults. Neotenic features