evolutionary psychology

Let’s Not Oversimplify Kim Kardashian’s Butt Appeal

Kim Kardashian at the 2011 MTV Video Music Awards.
Photo: Jason Merritt/Getty Images

Yesterday, Complex, jumping off a study by Turkish researchers covered in The Daily Mail, ran a piece titled “The Evolutionary Reason Why You Love Kim Kardashian’s Butt.” It was, as the name suggests, an attempt at understanding why Kardashian’s posterior has been an object of such fascination for so long, up to the point of it basically breaking the internet last month.

Complex explained the concept like this:

According to researchers from Bilkent University in Turkey (you guys are the real MVPs), the reason we’re so attracted to serious curves goes all the way back to our hunter-gatherer ancestors. You see, a woman having a back that curves approximately 45 degrees above the top of her butt means she would have had an evolutionary advantage in pre-civilized society. At least that’s what science says.

[The curve] would have enabled ancestral women to shift their center of mass back over their hips during pregnancy, a time during which there is a dramatic forward shift of their center of mass,” Dr. David Lewis told The Daily Mail. “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.”

There’s something intuitively appealing about this story — maybe because it takes a phenomenon that comes down to sex, a very primal subject, and explains it in terms of caveman urges that linger in our species to this day. That doesn’t mean the story’s accurate, though. In fact, it’s a good example of a pretty questionable type of evolutionary-psychology-based explanation for human behavior.

Evolutionary psychology, or evo-psych, refers to a branch of psychology that attempts to explain modern human behavior in terms of what would have been adaptive back in the days when natural selection determined the path of our species (natural selection still is doing that, of course, but thanks to our fancy medicine and technology, we’re tending to die in different ways than our ancestors did). To take a simple example, early humans (or ancestors of humans) who were really, really chill and never scared of anything probably didn’t survive for long, because if you don’t react to that saber-toothed tiger rustling the bushes near you with a bit of fear, you are going to be its dinner. Fear is an adaptive response to an environment in which stuff is trying to eat you, and so those who have some fear in them are more likely to survive and pass on their (somewhat fearful) genes. 

Fair enough: It would be silly to think that the distant past doesn’t still affect our behavior in certain ways. But the problems arise when you get too creative — or perhaps specific — with these explanations, which tends to happen when they’re not handled with care. I emailed Hunter Honeycutt, a psychology researcher at Bridgewater College in Virginia who has written at length about evolutionary psychology, to get his thoughts on this.

To Honeycutt, one of the clearest rebuttals to an evo-psych explanation for the Kardashian phenomenon is, as he put it, that “attractiveness is socially constructed, var[ying] among human populations across the globe and across generations.” In other words, if big butts are in today, but skinniness is seen as a desirable characteristic in women in other times and places, it doesn’t really make sense to say that it’s evolution that’s primarily shaping these preferences — culture is just a much more straightforward explanation.

Honeycutt also noted a number of other problems with this story line, some of which stem from the actual source study itself. For one thing, “men in the study were less attracted to larger rumps that resulted from fat or excess muscle” — the men’s preference had to do with spine curvature, not butt size, which would seem to conflict with the notion that Kardashian’s body is setting off some sort of primeval sex-bells.

But more important, Honeycutt nicely summed up the issue not just with this explanation, but with a lot of evo-psych stories:

The problem with such speculation is that I can come up with an equally plausible alternative scenario where this spinal curvature is maladaptive. For instance, it is reasonable to believe that foraging was a relatively dangerous activity in our distant ancestors, so women who foraged longer (particularly those who were pregnant and thus, heavier) would be at a significant increased risk of injury or death. 

Speculation about what would or wouldn’t be adaptive in an ancient setting is “difficult (if not impossible) to validate given how little we know about the social and environmental conditions in which our ancestors lived,” Honeycutt said. So just because a given story feels right or we find it appealing doesn’t make it true, especially when we can just as easily come up with debunking alternatives.

What’s most likely is that human behavior is an incredibly complicated mix of nature and nurture, and the “nature” part surely includes a lot of stuff that was partially a result of evolution. Evo-psych can help us untangle all this — it’s a discipline that has some useful concepts to teach us. But humanity’s response to Kim Kardashian’s butt, it would appear, resists any overly simple explanations.

Don’t Oversimplify Kim Kardashian’s Butt Appeal