It's funny you say that, because I was just watching a video of great apes looking at themselves in a mirror that scientists set up in the jungle. Once they got over the fear and realized they were seeing themselves, one of the things multiple apes did was look at their assholes.

Very curious that you thought about the fact that early humans had never seen their own assholes, as opposed to their faces.

Even after mirrors were invented, I still haven't seen mine..

I've seen my own asshole, it's not a particularly interesting view. I much prefer seeing someone else's.

I wonder if a human back then used the reflection from water at a lake or pond to see what their asshole looked like.

Or their own bald spot.

Uhm.. any reflective surface like water would do though?