Returning to some speculation that females with larger rumps are more masculinized, consider the fact that most porn stars have pretty nice derrieres but almost always require breast implants. It's not as if there aren't millions of females out there with large natural breasts, and who aren't fat. So why are they more or less absent from pornographic movies? It must be because breast girls have a bias toward more chaste, longer-term sexual strategies, while booty girls are biased toward less chaste, shorter-term strategies. The mechanism could be as simple as sensitivity to androgens.