Please don't associate that wonderful secondary sex characteristic, the derriere, with that horrible hopefully soon to be imprisoned ex pres!

The derriere actually evolved along with the achilles tendon, the nuchal ligament, and bodily hairlessness, so that we could run, and for miles and miles, which we did to wear prey animals out so that we could catch them, something Harvard's Daniel Lieberman has studied and written about. No other primate runs and no other primate has buttocks.