A woman with large breasts and a small waist. It’s what all men want, isn’t it? Western men are often cited as — or accused of — being obsessed with the large breasts/small waist ideal. It objectifies women, some women say.

That may be, but research has confirmed that Western men prefer this body shape. (It’s my guess, judging from the extreme manifestation of the same body shape type in manga, that Japanese men share that preference, but that’s another story.)

The question is, do men prefer the hourglass, Barbie body shape for cultural reasons (whatever they are) or is there an evolutionary basis for the preference?

It might irritate upholders of political correctness, but last week Polish scientists showed that women with large breasts and a small waist have higher fertility than women of other shapes. In other words, there may be a biological, evolutionary basis for the preference for the Barbie figure. We might still not like it, but it is not (just) a result of stereotyping and objectification.

A team led by Grazyna Jasienska, at Jagiellonian University in Krakow, Poland, measured 119 Polish women aged between 24 and 37. The team measured the women’s breast-to-underbreast ratio and waist-to-hip ratio. A high breast-to-underbreast ratio indicates that the woman has large breasts, and a low waist-to-hip ratio indicates a small waist.

The researchers found that women with both large breasts and a small waist had on average 26 percent more 17-b-estradiol in their blood (measured daily across the whole of the menstrual cycle) and 37 percent higher estradiol mid-cycle. Such women also had more progesterone than women in the other three categories.

The larger amount of these female hormones means that the women with large breasts and a small waist would be about three times more likely to get pregnant than women of other shapes. This qualifies the preference for that body shape as an evolutionary adaptation.

Evolutionary biologists say that something is adaptive if it contributes to greater reproductive success. So if men prefer women with large breasts and a small waist and this means they have more children, then we can conclude that the preference may have arisen for biological, evolutionary reasons.

Women with the three other categories of body shapes — narrow waist/small breasts, broad waist/large breasts and broad waist/small breasts — had similar, lower levels of female hormones. None were infertile, but the lower levels of hormones meant on average they were less fertile. None of the women in the study were using hormonal contraception.

It may be surprising that it’s taken this long for scientists to look for an evolutionary basis to the preference for large breasts and small waists. The toy maker Mattel, after all, has been making the Barbie doll since 1959. More than a billion have been sold. Over much of this time Mattel has been accused of propagating an unwelcome, unrealistic, male-fantasy image of woman.

It may be that the feminist movement, political correctness, and the row over the cultural impact of Barbie — and whether she causes anorexia, bulimia and general body-angst among teenage girls — has prevented biologists from thinking about sensitive subjects like the evolution of body-shape preferences.

So it helps that Jasienska, the leader of the Polish team, is a woman.

“Evolutionary biologists disagree about whether the male preference for narrow waists and large breasts is universal across cultures or functions only in industrial societies,” Jasienska said, pointing out that the preference does not seem to be shown in some traditional societies.

“Perhaps, in populations where women face severe energetic challenges, such as famine, signals about fecundity provided by body shape have tended to be much less informative for males than those provided by short-term, visible changes in body weight.”

In other words, in traditional, nonindustrial societies such as those in parts of Africa, simply being well-fed is the best indicator of fertility.

“However,” said Jasienska, “in Western societies, the cultural icon of Barbie as a symbol of female beauty seems to have some biological grounding.”

Mattel might be pleased to hear that. In 1998 the toy company brought out new versions of the Barbie doll, eight of which had fatter waists and smaller breasts. The idea, said Mattel, was to make the doll more contemporary. The company obviously also wanted to sell more dolls, but it probably also wanted to distance itself from charges that it was propagating a particular ideal of female beauty.

So, if an appreciation for large breasts and narrow waists has an evolutionary function, does that mean that us men can now freely ogle women like Pamela Anderson and Eiko Koike and plead “male genes made me do it”? No, because we have free will and are not slaves to our genes. Or we must accept a drink thrown in our faces while we whimper, “Sorry darling, it was my genes that made me do it.”

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