There's a scientific reason why men like big butts (and they cannot lie)

(L-R) Alia Wang, Aimie Wang, Kim Kardashian, North West, Kanye West and Nicki Minaj at the Alexander Wang Fashion Show in New York. (Photo by Craig Barritt/Getty Images)

Psychologists in the US have found an underlying reason for modern men’s preference for women with curvy backsides.

A study, in the journal Evolution and Human Behaviour, found that men prefer women with a 45.5 degree curve from back to buttocks.

The scientists say this angle is better able to support, provide for and carry out multiple pregnancies.

“What’s fascinating about this research is that it is yet another scientific illustration of a close fit between a sex-differentiated feature of human morphology — in this case lumbar curvature — and an evolved standard of attractiveness,” said the study’s co-author David Buss, a University of Texas psychology professor.

“This adds to a growing body of evidence that beauty is not entirely arbitrary, or ‘in the eyes of the beholder’ as many in mainstream social science believed, but rather has a coherent adaptive logic.”

There were two studies in the research. The first looked at vertebral wedging, an underlying spinal feature that can influence the actual curve in women’s lower backs.

About 100 men rated the attractiveness of several manipulated images displaying spinal curves ranging across the natural spectrum. Men were most attracted to images of women exhibiting the hypothesized optimum of 45 degrees of lumbar curvature.

“This spinal structure would have enabled pregnant women to balance their weight over the hips,” Lewis said. “These women would have been more effective at foraging during pregnancy and less likely to suffer spinal injuries. In turn, men who preferred these women would have had mates who were better able to provide for fetus and offspring, and who would have been able to carry out multiple pregnancies without injury.”

The second study looked at whether men prefer this angle because it reflects larger buttocks or whether it really can be attributed to the angle itself.

Men consistently preferred women whose spinal curvature was closer to optimum regardless of buttock size.

The 45 degree angles is close to the ideal. Image: The University of Texas at Austin

There is a whole body of scientific work on beauty.

One theory says beauty can be found in the relationship between the eyes and mouth. The distance between a woman’s eyes and the distance between her eyes and her mouth are key factors in determining how attractive she is to others.

There are two so-called golden ratios, one for length and one for width.

In experiments, Caucasian female faces were judged more attractive when the vertical distance between their eyes and the mouth was about 36% of the face’s length, and the horizontal distance between their eyes was 46% of the face’s width.

Psychologists theorise that this may be the reason why people are sometime unattractive after a haircut because the ratios change.

Other studies have found features such as large eyes or full lips make a woman more attractive.

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