system
Given the following post, respond as if you're commenting on Reddit:
human
Why does it take humans such a long time to become self sufficient after we're born?

It takes humans about 1 year before we are even able to stand up without holding on to something.  Why is it that compared to other animals, we take such a long time to develop into a being that can actually survive on our own without constant protection and assistance?
gpt
It's a balance between walking upright and having big brains.

Before we got big brains, our ancestors starting walking upright. This helped as it allows us see farther, it gave us the ability to engage in cursorial (endurance) hunting, and later gave us the ability to use tools while walking.

Our big brains give us intelligence and communication.

But there's a problem here; because of the way the femur fits into the pelvic bone, pelvic width has a limit in two-legged gaits. Once you go past that, you can't move as fast or be as stable; you lose agility. But to be born with a big brain, you have to have a big head which, in humans, would require a wide pelvis....catch-22.

We have developed a number of adaptations to deal with this. One is the fact that infant skulls don't fuse until later on, letting the head deform during birth. Another is the changing of the female pelvis during mid/late pregnancy; it changes shape temporarily and some of the connections alter, widening the opening for the baby. This is part of the reason really pregnant women "waddle" when they walk.

But the last gets at what you're talking about...we're born before we finish developing. Since being born with a fully developed brain would be too much of a fitness expense for the mother, a portion of development takes place outside of the womb. An infant can't walk or take care of itself for a long time because it isn't finished yet.

(edited for some typos & formatting errors)