Men lust for women with the traditional hourglass figure. Okay, that's not news. What is news is why they are attracted to this shape more than any other: Women who have large breasts and tiny waists may have the highest reproductive potential, giving a biological reason to men's proclivity for ladies who have a figure like a Barbie doll.

An international team of researchers from Jagiellonian University in Krakow, Poland and Harvard University in Boston, Mass., determined that women who have a relatively low waist-to-hip ratio and large breasts have 30 percent higher levels of the female reproductive hormone estradiol than do women with other combinations of body shapes, reports New Scientist. Previous research from Harvard has shown that higher levels of estradiol are related to higher fertility in women who are trying to get pregnant.

"If there are 30 percent higher levels, it means they are roughly three times more likely to get pregnant," lead study author Grazyna Jasienska, a human biologist with Jagiellonian University, told New Scientist. "In Western societies, the cultural icon of Barbie as a symbol of female beauty seems to have some biological grounding. I would be the last person to propagate Barbie. But when you think about the hourglass shape, Barbie is sort of the symbol."

The study: One hundred nineteen Polish women between the ages of 24 and 37 participated in the research. None of them were using hormonal contraception or taking any medication. Women who were extremely underweight or overweight were not included. Saliva samples were taken to measure estradiol.

The results: The women who had narrow waists and large breasts had on average 26 percent higher levels of the hormone 17-b-estradiol, than did women of other shapes. This peaked to 37 percent higher in the middle of their menstrual cycles. In addition, a woman's waist-to-hip ratio had a strong effect on her levels of progesterone, another female hormone.

Jasienska explained to New Scientist that a preference for low waist-to-hip ratios is a "universal feature" in psychological studies of men. "It was interesting to see what we observed in psychological studies has some biological background," she said.

The study findings were published in the Proceedings of the Royal Society.

Read the study for yourself. (requires Adobe Acrobat Reader...)