Eli5: Why are human babies born so ill prepared for the world, compared to some other mammals who are born much more well equipped?

Question

Eli5: Why are human babies born so ill prepared for the world, compared to some other mammals who are born much more well equipped?

In: 2

Answer 1

Primates have (relatively) very large brains, which means relatively large heads. If we tried to be born with full sized heads we’d kill the mother because our heads are too big to fit through the pelvis. So we’re born early, developmentally speaking, because that’s the longest we can stay “in” without drastically increasing the chance of death for both mom and baby.

Then we do the rest of our developing on the outside while our giant melons grow to full size.