Why Do Women Have Breasts, Anyway?

Afterward, we ate lunch at the small, creek-side home in the Wellington hills that Barnaby shared with his girlfriend, Monica, a Canadian graduate student studying bird behavior. She made a fantastic soup out of a roasted New Zealand tuber called kumara. A sign above the kitchen read, “Please do not feed the bear.”

It turns out I wasn’t the only woman whom Barnaby’s work made a little uncomfortable and self-conscious.

“Whenever Barny gives seminars on waist-to-hip ratios, all the women run home afterwards and measure themselves,” said Monica. (Barnaby’s studies and many others have established that men prefer a Marilyn Monroe–esque WHR of .7, meaning the waist is 70 percent the circumference of the hips. Some scientists hypothesize that this magic number represents an optimal level of health and hormones, but the significance of the WHR is highly controversial in the field.)

Barnaby looked mortified. “Yeah, well that’s unfortunate.”

“I measured mine,” offered Monica.

“How did it turn out?” I asked.

“I’m a .75.”

Barnaby himself doesn’t seem immune to his research. He wears, for example, a beard. In his cross-cultural anthropological studies, he has found facial hair to symbolize masculinity and authority. (His father, who teaches at the university and lives one town over with his wife, Amanda, and an eighty-pound English bulldog named Huxley, sports a bushy white mustache.)

Barnaby’s walls boasted several original Alan Dixson drawings, including one of a mandrill and one of a gorilla. Alan illustrates most of his own textbooks, while Barnaby supplies the computer graphics. Alan’s latest book is called Sexual Selection and the Origins of Human Mating Systems. In addition to their eight coauthored papers, they share a love of animals and a polite, diffident demeanor.

“Barnaby is like a mini-me of Alan,” said Monica, laughing. Born in England, the younger Dixson grew up in places like Scotland and West Africa, depending on his father’s posts. In Gabon, where Alan ran a primate center and studied sperm competition, Barnaby’s family had a pet monkey, a potto named Percy. Living closely among other animals made their behaviors, sexual and otherwise, seem perfectly normal. Barnaby’s older brother is also a scientist. His specialty is an enormous flightless cricket.

Both Alan and Barnaby believe studying mating behavior and sexual selection in primates can tell us much about our own reproductive organs. For example, men have relatively small testicles compared to other existing primates. Alan has written that this might indicate our early human ancestors were polygamous. (On this topic scholars vehemently disagree with each other. The field of evolutionary studies is a blood sport.)

To the Dixsons, enlarged human breasts, like giant testicles in chimps or the orangutan’s beard, are “courtship devices” born out of competition and selection. Large testicles produced more sperm, maximizing an individual’s chance that his genes, and not his rival’s, would penetrate the egg of a promiscuous female. The males with the biggest testicles had more descendants, who in turn had bigger testicles. The Dixsons believe beards and enlarged breasts, on the other hand, are seductive “adornments” advertising genetic quality. Those who attracted the best mates had fitter offspring and, ultimately, larger numbers of descendants, and so the traits persisted. This is the essence of sexual selection as posited by Charles Darwin.

 

“A lot has been written about what breasts might be telling a guy,” said Barnaby. “At its simplest, they’re telling the guy that this is a sexually mature woman. Beyond that, there are a lot of hypotheses. One that I find interesting, based on work on Hadza hunter-gatherers in Tanzania, is that there could be a profound preference among men for a nubile breast shape.” He explained that as women age and have more successive pregnancies (thus reducing her worth to a new mate), her breasts change. “I’m trying to find a nice way of saying it,” hedged Barnaby, “but age and gravity take their toll. The shape tends to lose its firmness and droops somewhat. This could be something that’s letting a man know about youth and fertility and potential reproductive output.” In other words, guys, go pursue someone a little more worthwhile, biologically speaking.

It’s a dog-eat-dog world out there.

The nuances continue. Large breasts sag more than small breasts, said Barnaby, so men likely prefer big ones because they are more “informative” of age. Other studies back up Barnaby’s hypothesis, some with real-life experiments. A few years ago in Brittany, France, a twenty-year-old actress of “average attractiveness” with relatively small breasts was given an unusual assignment: to sit in a bar while an undercover researcher recorded how many men approached her. Then she inserted enough latex padding into her bra to bump the cup size up to B and went to a neighboring bar. You can guess the third step: repeat with size C. She wore the same clothes in each bar, a pair of jeans and a tight-fitting sweatshirt. She was instructed to watch the dancing on the dance floor, but not to look at men along the edges. This was repeated for twelve nights over a three-week period.

When she wore the A-cup bra, she was asked to dance thirteen times. When she wore the B cup, she was asked nineteen times. And when her breasts grew to a size C? Forty-four dance cards.

In a similar experiment, Miss Elasto-chest tried hitchhiking by the side of the road, also in Brittany, at the height of summer and during the day. In her A-cup incarnation, fifteen men stopped; in her B cup, twenty men; and in her C cup, twenty-four men stopped. When the passing motorists were women, approximately the same number stopped for each cup size. Another study showed that waitresses with larger breasts get bigger tips.

NEXT: “The Urban Dictionary refers to this state as booblivious.”

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

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