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Applejuiceinthehall t1_ivc8ydl wrote

Reply to comment by Frequent-Seaweed4 in TIL that most non-human primate infants actively use their hands to help themselves out of the birth canal. Human infants do not, but their grip strength is much higher during the hours immediately after they are born. by afeeney

That was the idea, but it doesn't pan out when you look at the evidence. Some women can already accommodate that size skull. So if babies were born with a 3 month olds skull, then the selective pressure would be for wider hips.

Because of women with wider hips, we know that their walking/running isn't impeded with wider hips.

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Frequent-Seaweed4 t1_ivcb6wr wrote

Okay but you keep saying "some" women, when we're talking about the "average" woman.

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Applejuiceinthehall t1_ivceqf5 wrote

But it's only the average because human babies don't have skulls that are 40% of adult skull (which chimps have). If humans were born with that big of skull then women with wider hips would have been selected for and women with narrow hips would have been filtered out

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herbw t1_ivcftpy wrote

Human reproduction is complex system. The pelves of PG woman will expand due to a substance which causes the cartilage of the pelvic bones to relax, so the birth canal widens. to allow easier deliveries. When a pelvis of a woman who has given birth to a child/children is found we can see that on post mortem. How we know it.

Gestating babies, and delivering them is very complex system & has many, many interesting events going on, too.

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