Is it because of the whole big head/bipedalism thing? Other mammals can pop out babies in no time and it seems like that would be way more advantageous for multiple reasons (less stress on mom and baby, not in a vulnerable position for hours in the wild, etc). Why does the norm skew towards a day rather than hours?
In: 419
With bipedalism the pelvis had to decrease in size
But then with bigger heads a bigger pelvis is needed
So a good enough balance between the two evolved. This is why women have wider pelvises than men, if not for childbirth the ideal width would be that of a male pelvis
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