system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why is it that newborn mammals can walk after birth but newborn humans cannot?

Is it because they have to walk on only two legs instead of four?
gpt
Not all newborn mammals can walk after birth. The ones that can generally are species that need to be able to walk or they will be preyed on. So the ability to walk after birth is something evolution selected for.

Now humans take longer than most other mammals to develop because we are born very underdeveloped.  Our heads are huge and walking upright means our pelvises are narrow. That is not a good combination. Babies need to be born before the head grows too big, which means they are born relatively underdeveloped. However because humans are group animals who are capable of scaring off predators and carry their young, that is not a huge disadvantage. We are not impalas, whose only defence from predators is to run away. We are creatures who even in our early days were able to make sharp sticks and rocks and fire to keep predators on a safe distance.