Two points here. First, if eating meat is beneficial for our metabolism (in moderation) as would be implied by the brains thing, then doesn't this make us omnivores?
I stated no position on the matter, in fact I said I was on the fence.
Second, the whole men having sex with whoever they wanted bit is quite likely more mythological than factual. The ancient cultures we know of tend to regulate sex, not provide a free for all.
Perhaps they did, perhaps the ones before those which we know little to nothing of were more like packs of lions or other animals where an alpha males forces himself on the group. Still, not a basis for my ethical code.
If you can first outwit and slay me, else you're on my menu, big boy.