All share a very similar reproductive process, with similar hormones and outcomes. For example, regions of the Y chromosome cause the fetal gonad to secrete male hormones (androgens), which in turn modify the fetus – including its brain and genitals – to be a male. Without those hormones, the body would develop the appearance of a female.
This includes bearing the fetus, birth, and a long period of nursing and care preparing her offspring for independent life as adults.
Mothers' competence in non-human primates is related to their own hands-on experience in their youth. This may be true for humans as well.
Early maternal contact ('attachment') has important consequences for adult cognitive and social/sexual competence.
Compare with chimps where pink swellings advertise ovulation directly.
Human gestation would be 21 months if our brains were born at the same level of maturity as the average primate.
While human cervical opening is not much different from large apes, the immature human skull remains flexible enough to squeeze through just in time.
Although diet plays an important role, human auditory cortex may not be fully mature until late teens.
Ape mothers give birth on their own and infants are mature enough to support themselves on motherŐs hair within weeks.
At the same time, this prematurity makes both mother and neonate dependent on social support much more than other hominoids.
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