Science: Asking the Big Questions

The mystery: Why do women have prominent breasts, even when not lactating? 

It isn’t simply because we are mammals, all of which, as the word implies, sport mammary glands that produce milk. There are, after all, about 4,000 species of mammals, and we are the only ones to do so prior to lactation—as a predictable component of sexual maturation—as well as after.

Even our closest living relative, the chimpanzee, does not exhibit swollen breasts except when lactating, and even then, nothing on the human scale. You would probably have to look the crotch of a chimpanzee to tell it's sex (and even then, male chimpanzees don't begin to compare to male humans, but that's a story for another day).

So why do human females have such prominent features on their chest?  A couple theories:

Dedalus Devices?  In James Joyce’s Portrait of the Artist as a Young Man, Stephen Dedalus was musing with a friend on the nature of female beauty, whereupon he concluded that “you admired the great flanks of Venus because you felt that she would bear you burly offspring and admired her great breasts because you felt that she would give good milk to her children and yours.” Plausible enough, but there’s a problem: Breasts (except when lactating) are composed almost entirely of fat, not glandular tissue. If anything, in fact, there is a negative correlation between prelactating breast size and capacity to make milk! This leads to the intriguing (may I call it “titillating”?) prospect that those Dedalus Devices can be downright deceptive, promising more than they can provide, but successful as a mate-attraction strategy nonetheless because men have noticed that breasts swell so dramatically during nursing, thereby making them—blockheaded men, that is, who are already prisoners of their rampaging hormones—easy to swindle.

It has a bit of ring of truth to it, but as the author points out, it's not a perfect explanation.  But compared to the next one, it seems pretty solid.

Buttocks Substitutes? Some downright silly ideas have been advanced, one of the most notorious by British ethologist Desmond Morris, in his best-selling book, The Naked Ape. According to Morris, conspicuous breasts evolved in part because natural selection favors emotional intimacy between men and women as a result of the need for devoted biparental care of offspring. Most mammals mate dorso-ventrally (“doggy style”), which—although feasible for human beings, too—is less personal and thus, less likely to generate emotional bonding than is face-to-face intercourse. To induce ventral-ventral, face-to-face love-making, then, evolution supposedly favored conspicuous bilaterally paired breasts, which essentially mimic the buttocks of “normal” quadrupeds, and assist in the transition from dorso-ventral to frontal copulation.

I don't see it, honestly.  I can tell the difference.

Really, there's nothing wrong with having multiple reasons for a feature to evolve.  The author promises even more hypotheses soon.  I look forward to posting on his next effort...

I myself prefer a simpler explanation:

Thanks to Jake Finnegan who picked up this link in his Burkalesque Babe: Kim Kardashian,