Morris (an anthropologist, I think) wrote a very influential and popular book back in the 60s or 70s ("The Naked Ape") on what today might be called evolutionary psychology. If I recall correctly, his thesis was that our sexual behavior evolved and that it manifested itself today to factors that could be traced back to our time on the savanna. At lot of it made sense to me at the time, although like most pop psychology books, he did get carried away on a few things. It's still worth reading today, although many of his insights have been so incorporated into contemporary psychology that it's hard to believe how sensational and scandalous the book was when it first came out.

If I remember correctly, round breasts and red lips were signals to evoke male sexual responses based on their similarities to buttocks and female genitalia. I also recall something about the role of pubic and underarm hair as sexual signals, even after the rest of the body lost it's hair (also for sexual reasons). It's not fair for me comment too much on the book since I read it so long ago, but I was impressed by it, except for a few comments he made I found hard to accept because his conclusions seemed pulled out of thin air. Psychology is like that; his biology was much better than his psychology, as I recall. I would definitely recommend the book. It's probably available in a revised edition including modern research. Like most psychology, its about a 50-50 mix of the obvious and the unprovable.

Now that I've written these lines, I realize that that book was extremely influential in the development of my thought and opinions, even though I remember very little of what it was actually about. You pick up ideas, they change your head, and your head stays changed long after the ideas are forgotten.

I saw Morris on TV the other day, on a special on biology, and he seems to be still following the same type of research he was back then. It was like running into an old friend.