Did you know that kissing might not be as uniquely human as we thought? Prepare to be amazed: Scientists have uncovered evidence that the intimate act of kissing predates humans by millions of years! While we often associate kissing with our own species, researchers have observed similar behaviors in various modern primates, including chimpanzees, macaques, and baboons. But here's where it gets fascinating: a team of scientists from the University of Oxford, University College London, and Florida Institute of Technology decided to dig deeper—not just to find out when our ancestors started kissing, but which animals were the first to lock lips.
To tackle this question, the team first had to define what constitutes a 'kiss.' After all, animals often smack their lips during less intimate activities, like fish 'kiss-fighting' or ants transferring fluids mouth-to-mouth (a behavior called trophallaxis). Their solution? A precise definition: kissing is a 'non-agonistic interaction involving directed, intraspecific (same-species), oral-oral contact with lip/mouthpart movement and no food transfer.'
Using this definition, the researchers analyzed observational data from modern primate studies and fed it into a model to reconstruct the evolutionary history of kissing. The results were astonishing: the act of kissing traces back to the last common ancestor of humans and great apes, which lived approximately 21.5 to 16.9 million years ago. And this is the part most people miss: even Neanderthals, our closest extinct relatives, likely kissed too! A 2017 study compared microbes in a 48,000-year-old Neanderthal's dental plaque with those in modern humans and found striking similarities, hinting at shared kissing behaviors.
But it doesn’t stop there. The researchers also discovered that Eastern gorillas, unlike their Western counterparts and other great apes, don’t practice kissing. Similarly, the ancestors of macaques and baboons didn’t kiss, suggesting that the behavior evolved independently in these groups. Controversial question: Does this mean kissing isn’t as universal as we thought, even among closely related species?
As for why our ancestors started kissing, theories abound. Some argue it strengthens social bonds, boosts reproductive success, or even enhances immunity through microbe exchange. Others, however, point to its risks, like the spread of deadly diseases. One intriguing theory is that kissing evolved from premastication—a practice where parents pre-chew food and transfer it mouth-to-mouth to their infants. Over generations, this behavior may have transformed into the affectionate act we know today.
Food for thought: If kissing evolved from a practical feeding behavior, does that make it less romantic? Or does it simply highlight the beautiful complexity of evolutionary adaptations? Share your thoughts in the comments—we’d love to hear your take on this ancient, intimate gesture!
