Sometimes, reading scientific literature can feel like an unbearably dry, overwhelmingly jargony slog. But sometimes, if the reader is lucky, they’re rewarded for their efforts with sentences like this one: “The human face, with its distinct features such as eye-whites, eyebrows, red lips and cheeks signals emotions, intentions, health and sexual attraction and, as we will show here, shares important features with the primate behind.”
That’s from a study published last week in the journal PLOS One, which found, as you can probably surmise, a delightful similarity between our faces and chimpanzee butts, the latter of which also sounds like something a prepubescent boy might name his band.
As my colleague Melissa Dahl has written, scientists believe that faces hold a special place in our brain (literally — there’s a region dedicated specifically to facial recognition, called the fusiform face area). And past research has shown that when we encounter a face, we have a particular way of making sense of it: The brain will process the whole thing at once, rather than going feature by feature (which is why it takes us a little longer when a face is taken out of its usual context, like if it’s upside-down or turned on its side).
And butts, it seems, are to chimps as faces are to humans. As Nathaniel Scharping explained in Discover, the authors of the PLOS study set up their volunteers with a matching game, asking them to pair up identical sets of human faces and then identical sets of butts. The results pretty much adhered to their expectations: When the images were flipped, people were worse at recognizing upside-down faces, but no slower at recognizing upside-down behinds, which don’t spark that same neurological process. When they did the same activity with chimpanzees, though,
the researchers found that they got a lot slower at recognizing the butts when they were flipped around — the same result as with humans and faces, and an indicator that chimpanzees are adapted to recognize each other by their rear ends. They also took it a step further and made the images black and white to remove the color clues that chimpanzees could pick up on. Flipping the images upside down seemed to matter less when black and white images were used, which indicates that color plays an important role in picking out individual behinds from the crowd as well.
Before you start snickering at those silly apes, though, consider this: Visual recognition isn’t the only thing your face has in common with a primate’s rear end. “The findings suggest an evolutionary shift in socio-sexual signalling function from behinds to faces, two hairless, symmetrical and attractive body parts, which might have attuned the human brain to process faces, and the human face to become more behind-like,” the study authors wrote. Simplified from the biology jargon: Your face may have evolved to resemble the ass of your ancestors. If the band doesn’t pan out, at least the prepubescent boys of the world can mine science for some pretty good burns.