Why men favour rounder bums
Last year saw the emergence of the 'belfie' thanks to Kim Kardashian and her impressive curves. For anyone who managed to avoid the phenomenon a belfie is a selfie that shows off the owner's butt. We all know these kind of snaps drive most men wild, but now there could be a logical reason why they're so drawn to big behinds.
According to new research, it's actually the curved spine men find themselves attracted to. That's because in hunter-and-gatherer societies this shape suggested the woman would make a better gatherer than someone with a straighter spine.
"[The curve] would have enabled ancestral women to shift their centre of mass back over their hips during pregnancy, a time during which there is a dramatic forward shift of their centre of mass," Dr David Lewis, a psychologist at Bilkent University in Turkey, said.
"This benefit is critical: without being able to do this, women would experience a dramatic increase in hip torque [pressure], subjecting them to risk of muscular fatigue and injury.
"Consequently, ancestral women who possessed this degree of lumbar curvature would have been able to forage longer into pregnancy and would have been able to carry out multiple pregnancies with a reduced risk of spinal injury."
So while extra buttock mass might cause the spine to appear more curved, it's not the actual butt that's attractive to males, the study claims.
According to the researchers, a 45-degree angle is perfect, as this aids movement but isn't extreme enough to cause back pain.
To reach this conclusion, published in the journal Evolution and Human Behaviour, psychologists showed 300 men silhouettes of women with varying angles of spine curvature. The participants were then asked to rate attractiveness for each silhouette.
Results showed men were significantly more attracted to women whose spines curved by 45.5 degrees. However, butts didn't come into it much.
"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 Lewis explained,
"Alternatively, men may have preferences for both lumbar curvature and buttock size.
"Future research is needed to better understand the latter."