Planting a big wet smooch on someone you love didn’t start with us. Well, technically it did, just not the version of us around today. According to new research, kissing may have begun with our great ape ancestors around 16.9 to 21.5 million years ago.
Researchers from the University of Oxford took the first wide-angle evolutionary look at the biological origins of kissing. Lead author Matilda Brindle and her team had to begin by defining what counts as a kiss across multiple primate species. After ruling out behaviors that looked like kissing but were actually just food delivery systems, they landed on a definition for a romantic gesture that, in typical scientific fashion, has been stripped of all romance: non-aggressive mouth-to-mouth contact without the transfer of food.
Doesn’t that description make your heart swoon?
Armed with a definition that seems like a sitcom parody of how a scientist would understand affection, the team gathered every documented instance of kissing in modern monkeys and apes, including chimpanzees, bonobos, and orangutans. Then they ran 10 million computer simulations to reconstruct the probability of kissing behaviors in long-extinct primate ancestors. They found that kissing most likely evolved early in the great ape family, and the trait just stuck around.
You may have already pieced together one implication of all of this: this might mean Neanderthals kissed, too. Science already knew that Neanderthals swapped genes and saliva with early humans, though now it seems like they shared a few passionate pecks, too. However, the exact nature and purpose of those kisses remains a mystery. We may never know if the kisses were for romantic purposes or served some other kind of social function.
Now, none of this is 100 percent certain. This was all based on computer simulations and not observed data, and also keep in mind that, as study co-author Catherine Talbot pointed out, kissing “is only documented in 46% of human cultures.” In other words, there’s plenty of room for this theory to prove incorrect, and the researchers are well aware of that.
Still, as is often the case with these studies that reveal fascinating, potentially groundbreaking preliminary findings, it’s something other research teams can build on (or completely dismantle) in the years to come.
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