Why Do Women Have Breasts, Anyway?

Steven Platek, an evolutionary neuroscientist from Georgia Gwinnett College, showed college men pictures of breasts while he scanned their brains in an MRI machine. Not so surprisingly, he found the breast images triggered the “reward centers” in the volunteers’ brains. “Most of the images capture the attention of the male so much so that it will distract his mental and cognitive processes in ways that could be dysfunctional in other capacities,” Platek told me. The Urban Dictionary refers to this state as booblivious.

Okay, so men are distracted by breasts. All of this sounds familiar to us in Western cultures, but there are problems with making sweeping statements about evolution based on studies about male behavior in pubs. For one thing, I am still hung up on the nubility hypothesis, which might as well be called the sag hypothesis. But speaking from personal experience, I can report my breasts actually got bigger and fuller after pregnancy. I really can’t say they are sagging, not yet anyway. I am well past the age of what anthropologists call “peak reproductive value.” Does a man really need breasts to tell him a woman is getting on in years? Aren’t there more obvious signs that don’t require awkward social glances? And as anyone who’s been to a public shower or springtime college campus can tell you, there is an enormous, and I mean enormous, variety of breast sizes and shapes out there. I’m talking 300 to 500 percent differences in volume, and these are in women of roughly the same age. What other body part is so variable, I ask? If breasts were such important communicators, wouldn’t they be more on the same page?

Further complicating the picture, there is also great variety in men’s tastes. Barnaby conceded that male preferences aren’t as universal as he’d hoped. He expected all men to prefer breasts of a similar size—namely, big. But that doesn’t always happen. In his earlier data from the eye-tracker, which he published in Archives of Sexual Behavior, the same number of men preferred medium breasts to large breasts, and some men were most enthusiastic about small breasts. And these were all straight, white men from New Zealand. Other studies have shown that Azande and Ganda tribesmen prefer long and pendulous breasts, whereas the Manus and Maasai prefer more rounded ones. One study found that Western men prefer curvier women during a recession, perhaps for their suggestion of comfort and ample calories. In his own study, Barnaby found that men simply liked staring at all breasts, regardless of size or how attractive the image was rated.

If breasts serve as such a great signal of a woman’s fitness, so should the areola, posits Barnaby. Younger women who have never had children have lighter areolas, so Barnaby expected men to prefer lighter pigmentation when they rated images in another study. He was surprised to learn that many men like darker, post-pregnancy areolar pigment. Similarly, data on preferences for areolar size were all over the map. And while most men seem to like breasts, in many places breasts are merely pedestrian. Not every culture has a Hooters. The nape of the neck is unbearably sexy in Japan. Bootylicious is where it’s at in parts of western Africa and South America. When my son was little, he used to mortify me by going around the house singing a Sir Mix-a-Lot song from the Shrek soundtrack: “I like big butts and I cannot lie.”

Barnaby knows about these inconsistencies, and they cause him some academic heartburn. But while he acknowledged the data are far from conclusive, he still thinks they hold up. “The amount of visual attention and the amount of evidence that men are attracted to breasts would lead you to think something is going on in evolutionary terms with mate choice and breast morphology.”

Barnaby is just the latest in a long line of scientists who have been thinking about how the breasts evolved in step with the male gaze for at least half a century, ever since Desmond Morris published his famous and influential book, The Naked Ape, in 1967. (Morris, a British zoologist, is also known for choreographing the gestures and grunts of the actors in Quest for Fire.) In The Naked Ape, he attempted to explain to a popular audience why humans act the way they do. Describing a prehistoric life very much like the suburban dead-zone of the mid-twentieth century, Morris wrote how out of the Pleistocene emerged “Man the Hunter,” unique among primates, who came home after a hard day of stalking beasts and needed his hearth-bound woman to show him a stimulating set of knockers. Without them, he’d have little inclination to stick around and provision the family. (Never mind that hunter-gatherer women procured most of the daily food for their families; that research came later and Morris still has not adjusted his breast-origin hypothesis.)

Since Mrs. Mighty Hunter had to be constantly sexy for this scenario to work, she needed a big front-and-center sexual organ different from what all other primates who did not walk upright on two legs had. Those primates signal sexual readiness, their estrus, with swollen buttocks or labia. “Can we,” asked Morris, “if we look at the frontal regions of the females of our species, see any structures that might possibly be mimics of the ancient display of hemispherical buttocks and red labia? The answer stands out as clearly as the female bosom itself. The protuberant, hemispherical breasts of the female must surely be copies of the fleshy buttocks, and the sharply defined red lips around the mouth must be copies of the red labia.”

I may never again think of lipstick the same way.

Today, The Naked Ape reads like an embarrassing manifesto of male dominance, presented at exactly the same time the women’s lib movement was heating up. Just as Linnaeus appeared to be pushing a political agenda in naming us Mammalia (nudging women to act more maternal during the Enlightenment), perhaps Morris was too. On the other hand, maybe Linnaeus and Morris and the whole lot of them were really just breast men.

NEXT: “Try telling some feminist anthropologists that breasts exist because of men, and you might get whacked in the head by a rubber Australopithecus pelvis.”

TAGS: breasts and natural and unnatural history | florence williams | why do women have breasts

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