Question

Why new born humans have such a small brain

Answer 1

Because as humans grow bigger, so does there brain. So the smaller you are, the smaller your brain.

Hope this helped!

-Edge

Answer 2

If women's hips were bigger the baby would continue to grow inside the women, but because of the small size of the hips the baby would have to come out sooner. + Babies brains grow bigger as their bodies do, so their brain doesn't stay the same size.