system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is there more (aparrent) variance between the faces of humans (to the point where the human face is instantly recognizable) than those of other species?

For example, I can easily tell apart my dad's face from my friend's face, but all of the squirrels that run around in our backyard look the same. Does it have to do with our brains, or is it a matter of practice (so that to an infant, all faces *do* look the same)? Or is it that human faces are inherantly more variable than the faces of other animals?

I've wondered this for a long time...

(I think this falls under biology but may as well be culture or another tag.)
gpt
There is literally a part of the human brain (right fusiform gyrus, in the lumpy gray section) dedicated to facial recognition, separate from the other parts that recognize color and shade patterns. We need to see faces for many reasons: communication, response, survival etc. You could say we're just built for it. Prosopagnosia is a disease that disables that part, so everybody looks like a Picasso painting.

Edit: not exactly like a Picasso, clarified in the comment below.