Another thing i found fascinating is that a man does not even need an erection or physical stimulation to cum.
All that is needed is stimulation of a certain group of muscles in the groin to start contracting. This caused by brain stimulation and totally unconsciously can cause a wet dream.
I once knew a woman who could make herself cum by just thinking about sex . she didn’t even have to tighten her pussy or grind /cross her legs or anything else.
They say mankind and chimps are one of the few animals that we know who can just have sex for the fun of it.