I used to love Desmond Morris' television shows. The idea of presenting human behavior in the same manner as one would present animal behavior of various sorts was a great way to remove our cultural biases toward the exceptionalism of humankind (is human exceptionalism a term? If not, it should be - Oops, apparently it is).
What's funny is that I remember an episode detailing the similarities between breast and buttock cleavage. And I just took it for granted, ten years ago when I saw it rerunned on the Discovery Channel. Cleavage = sexy.
Except recently I started thinking about the bras from the 50's with their "lift and separate" approach, which was hardly conducive to a style of cleavage equivalent to the buttocks.
So perhaps fashion does construct sexy... more than just a thin vs curvy dynamic as models yo-yo back and forth in weight. We know that erotic parts on bodies are different from culture to culture, Africans tend to prefer the buttocks, while Americans prefer the breasts. Evolutionary biologists work desperately to explain how cultural features can come from evolutionary drives, so breasts = buttocks = display of estrus = sexual receptivity. Unfortunately, as pointed out in some articles on Slate a few months ago, evolutionary biology is like a conspiracy theorist - an explanation can always be found, no matter how pear-shaped the facts.
1) Women cheat as much as men. Of course, say the evo-bio's, women would choose a long-term partner for security, and then mate (cheat) with the young, healthy, sexy man who can provide good genes, even if fidelity/responsiblity isn't one of those genes.
2) Women cheat less than men. Of course, say the evo-bio's, pregnancy is a resource-intensive process, and women will look to mate with men who can provide those resources. So those who can provide will pass on the provider gene to their offspring and thus be more successful
Any way the data goes, evo-bio can find a reason for it. That's not really science.
Although I would love to hear the explanation for the torpedo boob look.