Evolutionary Beer Goggles

I was reading this article on the Sciam blog when I ran into discussion about how fish had to evolve completely new bone structures to live on land. It got me back on my favorite evolutionary hobby horse. Allow me to demonstrate:

At some point in our evolution, humans developed a radically different pelvic/spinal structure that allows us to walk upright comfortably. I know all the yadda, yadda about evolutionary advantage, but how did those first couple of generations become dominant enough to breed? Apes are, for the most part, harem animals. So here's my theory: It came through the females. I've got two scenarios:

A. Joe Ape stumbled across some fermented fruit, had a few too many, and comes home thinking, "I've never tried that deformed one. I think I'll get me a little strange tonight. Sure, she's a little tall, but they're all the same size kneeling down."

B. Jim Ape, not the dominant guy, thinks: "Ape, I'm never gonna get laid. Not unless I start my own gig. That tall chick is trying to mother all the other women's babies, but Joe won't do her. I bet I could get her to elope with me."

Ok, so they're highly anthropomorphisized, but major mutations like that just don't make sense in species that select mates. Call it the Beer Goggles Corollary to Evolution.