Autolykos:
Well, they could be our closest animal relatives. Their sexual habits are extremely - shall we say - human, even moreso than chimpanzees.
One piece of evidence I forgot to mention is the so-called “hidden estrus”. Human females are sexually receptive basically all the time. There are no outward fertility signs that appear during ovulation. Bonobo females are also sexually receptive all or most of the time, but instead of a “hidden estrus”, they display prolonged or permanent signs of estrus. Either way, both human and bonobo females hide their actual fertility from males. I think this may be an even more important check on male sexual domination than promiscuity or bisexuality.
This is a great thing about human females: they’re all ready to be seduced at any time if you just get take a few minutes to get their instincts working.