You've probably heard it on TV and social media. This is the "Age of the Big Butt," where society's concept of beauty is increasingly coinciding with sex appeal and a love for curves. A large-but-toned backside in particular is supposedly the new vogue (even if men have been staring at them for centuries). Now, researchers from The University of Texas (UT) at Austin explain that our fascination with the butt is being driven by evolution, and it may actually be all about the spine.

"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," David Buss, a UT Austin psychologist said in a recent statement. "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."

In other words, as humanity continues to modernize, our concept of beauty might be regressing back to its basic evolutionary roots - that is, a beautiful woman is one that can bear healthy children.

Buss recently co-authored a study published in the journal Evolution and Human Behavior, in which 100 men were first asked to rate the attractiveness of several images of a woman's silhouette as she stood sideways. Each image was manipulated to represent a different spinal curvature with the same backside mass. (Scroll to read on...)

Interestingly, the men consistently chose women with a 45.5 degree curve from back to buttocks - something that theoretically would have allowed our ancestors to better support, provide for, and carry out multiple pregnancies even with a nomadic lifestyle.

"These women would have been more effective at foraging during pregnancy and less likely to suffer spinal injuries," study lead David Lewis explained. "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."

And if body-type preference has genetic influence, this would mean that more and more of each ancestral generation would have taken a liking to women with this ideal curve.

In a second study, the researchers asked 200 men to look at groups of women with different buttock size and vertebral wedging. It was found that despite the fact that some women had larger butts than others, it was again spine curve that dominated their choices, with the optimum curvature consistently the "sexiest" of the choices. (Scroll to read on...)

"This enabled us to conclusively show that men prefer women who exhibit specific angles of spinal curvature over buttock mass," co-author Eric Russel added.

So why can't everyone stop talking about big butts? It's important to note that despite how dense a female's backside actually is, a 45.5 degree curve will make her posterior look bigger, as it protrudes more obviously than a lesser curve. This could explain why women in high heels are attractive as well, as it forces women to curve their body for balance.

Of course, "I like a 45-degree spine and I cannot lie" isn't nearly as catchy as "big butts," and telling a woman you like the curve of her spine just sounds outright creepy. That's why it may be better to just stick with what society thinks it's obsessing over, even when the truth is far more complex.

Who says science had to be sexy anyways?

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