A new study challenges the common perception that the hourglass figure for females – tiny waist, big breasts, and curvy hips – is considered the perfect feminine shape. Scientists have long said that women with curvy hips are healthier and have more babies. More specifically, a curvy waist-to-hip ration of 0.7 or lower is associated with higher fertility and lower rates of chronic disease. More than that, men prefer women with a curvy waist-to-hip ratio of 0.7 or lower. Evolutionary psychologists explain that the low ratio is a reliable single of a healthy woman with higher fertility.

For the study, published in Current Anthropology, anthropologist Elizabeth Cashdan of the University of Utah analyzed data from 33 non-Western populations and four European populations and found the average waist-to-hip ratio for women is above 0.8. Androgens, which include testosterone, increase waist-to-hip ratios in women by increasing visceral fat, or belly fat. The hormones that make women physically stronger, more competitive and better able to deal with stress also tend to redistribute fat from the hips to the waist, Cashdan explained. “The hormonal profile associated with high [waist-to-hip ratio] . . . may favor success in resource competition, particularly under stressful circumstances,” writes Cashdan. “The androgenic effects—stamina, initiative, risk-proneness, assertiveness, dominance—should be particularly useful where a woman must depend on her own resources to support herself and her family.”

Another interesting idea to keep in mind is the fact that in countries where women tend to be economically independent, like Britain or Denmark, men may prefer the non-hourglass shape. In countries where women are economically dependent on men (such as Japan, Greece and Portugal) men prefer the common ideal of female beauty, which is the hourglass shape. At the same time, in some non-Western societies where women bear the responsibility for finding food, men prefer larger waist-to-hip ratios.

As a general idea, women from around the world tend to have larger waist-to-hips ratio than the optimal ratio, as considered by medical and social stands. Cashdan suggests the differences between men’s preferences in some societies have to do with sexual equality.