where his civilizations, including our own

I don't know, are you? There are two possible meanings for "top and bottom". One is literal: "penetrative and receptive". The other is figurative: "dominant and submissive". Obviously, they don't have to correspond in real life, but frequently people creating fiction use the convention that they do. I don't really care for that convention, so it would be meaningless to count how often a character was fucking as opposed to getting fucked in my writing.