Kim Kardashian

It’s no secret that big hips and booties have shot to the forefront of what is considered sexy in today’s society, but why?

A new study attempts to find the science behind men’s interest in voluptuous figures.

“Over the course of human history, women faced the adaptive problem of a forwarded-shifted center of mass during pregnancy,” study co-author Eric Russell, a graduate student in psychology, told The Huffington Post in an email. “Women with a greater degree of lumbar curvature … were able to redistribute this center of mass to reduce the strain of pregnancy. Thus, we hypothesized that men should have a psychological adaptation to prefer these women as mating partners.”

In short, men’s preference for larger booties likely evolved because it enabled women to sustain multiple pregnancies without injury and to forage productively during pregnancy.

The study surveyed more than 300 men, who rated the attractiveness of female silhouettes that had lumbar curvatures ranging from 26 to 61 degrees. The majority found a moderate curvature — about 45.5 degrees — to be just right. The researchers also found the structure of the spine itself, rather than just the buttocks’ fat and muscle, is key.

“Men may be directing their attention to the butt and obtaining information about women’s spines, even if they are unaware that that is what their minds are doing,” Dr. David Lewis, a psychologist at Bilkent University in Turkey and the study’s lead author, told the Daily Mail. “Alternatively, men may have preferences for both lumbar curvature and buttock size. Future research is needed to better understand the latter.”