Do the other primates all mate doggy-style-- are humans the only ones who ever do things face-to-face? And if so, is that true across all modern humanity? And if so, when did that start, historically? I am curious.

I hadn't heard the explanation that humans were paedomorphic like domesticated dogs, and I think it's fascinating. [Perhaps I'm not a good person to reason about it, though, because all I remember about the fox domestication experiments is going "omg squee so cute!" :) ]