While we're on Nessus, this is little sketch I did for no reason, then added text on a whim. My roomate, you see, had recently given me grief on pairing a centaur with a human female, stating that, and I quote, "Ruptured intestines is the leading cause of death among female bestialists".
Consider that in Greek mythology (not Roman, mind you, Greek), there were no female centaurs, and they propagated quite efficiently with human females. Well, if the sex is that bad, can you imagine the birth? Ouchies.