Imagine recognizing people you know, friends and family, by looking into their rear end. That’s how chimpanzees do it.
The way we humans recognize each other is actually slightly more complex than by observing and memorizing distinct features of each others’ faces. It is less recognizing a nose and a mouth, and more something called configural recognition that processes the entire facial structure altogether. This is the reason people take a second to recognize a face that’s upside down. But chimpanzees recognize each other another way.
According to a study published in the journal PLOS One, Dutch and Japanese researchers have discovered that chimpanzees look at other chimpanzees’ butts like humans look at other humans.
The scientists observed chimps as they were given photographs of buttocks belonging to other chimps, and then had to couple two identical photographs on a touch screen. The primates seemed to be slower at recognizing the posteriors when they were rotated 180 degrees to the side.
When it came to humans, their recognition of faces,like the chimps, was slower when flipped upside down. However, this stall didn’t appear when they were presented with upside down pictures of human behinds.
The scientist believe that chimpanzees developed the ability to recognize butts the same way we evolved to recognize face, we each just started recognizing what we faced the most.
Chimps spend most of their time moving in groups, making a chimps only view butts of other chimps. And since ovulating females usually have red and swollen rear ends, it works in the male chimp’s benefit to recognize them. The males use this system to separate ovulating non-relatives from ovulating relatives, preventing inbreeding.