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Seeing Curves From a New Angle


Female warblers go gaga for potential mates who serenade them with extensive song repertoires.

Red jungle hens favor a rooster not for his strutting, heft or fineness of feathers, but for the length of his comb and the brilliance of his wattle.

The female scorpion fly is a stickler for symmetry, losing her head over a fella with wings identical in length, width and shape.

While the criteria vary, the warbler, jungle hen and scorpion fly share the same biological motivation: selecting the healthiest suitor available, the better to produce disease-resistant offspring.

Scientists have established that warblers with big playlists, long-combed roosters with bright wattles and symmetrically perfect scorpion flies are healthier, stand a better chance at copulatory success and produce offspring that are more disease resistant than do their less body-beautiful competitors.

Human preferences are also built upon certain aesthetics that ensure a mate isn't passing along damaged goods. Like the scorpion fly, we size up the physical form of a potential mate as a semaphore of good health.

But Devendra Singh, a University of Texas psychologist, has ferreted out one mate preference detector that is singularly Homo sapiens: that universal measure of sexual allure, waist appeal.

Both sexes consider the va-va-va-voom from hip to waist in mate selection, but physique is more important to men, studies indicate.

Boys and men of various backgrounds, ages and nationalities were shown line drawings of female figures with varying waist-hip ratios and asked to rate them on attractiveness, sexiness, fertility and health. Women also ranked the drawings. The favorite was a figure of average weight with a waist 70% the size of her hips, or a .7 ratio. (Translation: roughly a 25-inch waist with 37-inch hips. Popular as they are, breasts were not factored in, but the bottom half of the hourglass figure fits the ratio.)

The only sex difference evident in the survey was women rated an underweight figure drawing as equally attractive as the normal weight figure while men did not.

While a smaller waist set upon wider hips is an undeniable characteristic of what is cross-culturally identified as "sexy," it's also a reproductive calling card: "I am a goddess of health and fertility." (It's no accident that we are celebrating the 50th anniversary of the bikini.)

"Human beauty ideals have biological meaning," Singh says. "Yes, people always said they liked the hourglass figure, but they did not know that the waist-hip ratio was a health certificate. If women don't have the right hormonal conditions, they won't have the right fat distribution. Notice I did not say a woman who is healthy, fertile and skinnier. A healthy, fertile woman can be 140 or 110 pounds and still have a waist-hip ratio .7."

Before puberty and after menopause, the sexes have roughly the same waistline. Post-puberty, the average girl amasses nearly 35 pounds of estrogen reproductive fat padding her hips and thighs, a savings account of fuel capable of sustaining pregnancy and a year of lactation (at a cost of 180,000 calories or hundreds of pints of Haagan Dazs) during a brief famine. Boys lose weight at the hips and thighs with testosterone fueling muscle mass in the shoulders, arms and chest.

Most women's waist-hip ratio ranges from .6 to .8 during the reproductive years, Singh says.


Growing evidence suggests that the waist-hip ratio is a reliable indicator of fertility and absence of conditions such as diabetes, hypertension, cardiovascular disease, gall bladder disease and cancer of the breast, cervix and ovaries.

A 1993 Dutch study of 500 women seeking artificial insemination, most because their partners were infertile, sterile or had genetic abnormalities, found that a woman's chance of conceiving decreased 30% for every 10% increase in her waist-hip ratio, regardless of weight. (The greater the difference between waist and hip size, the lower the ratio.)

Estrogen seems to lower the ratio while testosterone increases it. Women with polycystic ovarian syndrome have elevated testosterone and higher waist-hip ratios. Menopausal women taking estrogen-enhancing medication, who are not obese, develop lower waist-hip ratios than comparable women not taking enhancers, a study found. Still other problems--such as anorexia, obesity and production of excess androgen, a male sex hormone--cause ovulatory dysfunction while affecting waist-hip ratios.

But can it be that the attraction of below-the-navel curvaceousness can be isolated to nothing more than a biological courting trigger?

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