system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why don’t chimpanzees and other primates have buttcheeks like humans, but instead protruding buttholes?
gpt
They do not walk upright on two legs, or at least do not do so often enough to develop glutes. 

The entire reason that we have butcheeks is that they are our glute muscles that allow us to control balance and power our walking and running on two legs.