Scientists have made a groundbreaking discovery about one of humanity's most intimate gestures - the kiss. A comprehensive evolutionary study has revealed that romantic kissing dates back much further than previously imagined, with evidence suggesting it emerged more than 21 million years ago.
The Ancient Origins of Intimate Contact
Researchers from the University of Oxford have pushed the timeline of the "first kiss" deep into our evolutionary past. According to their findings published in Evolution and Human Behaviour, kissing likely appeared long before modern humans walked the Earth. The behaviour was probably practised by the common ancestor of great apes approximately 21.5 million years ago.
Lead researcher Matilda Brindle from the University of Oxford explained their methodology. "We began with a fundamental question: if kissing offers no clear survival advantage, why is it so common across species?" The team established a specific definition for kissing behaviour: non-aggressive, mouth-to-mouth contact involving some movement, without food exchange.
Kissing Across the Animal Kingdom
Once researchers defined what constituted kissing behaviour, examples began emerging throughout the animal world. The study documented kiss-like behaviour in wolves, prairie dogs, and even polar bears who engage in exaggerated "tongue-heavy" contact. Some bird species, including albatrosses, also demonstrate similar mouth-to-mouth interactions.
However, the primary focus remained on primates. "Humans, chimps, and bonobos all kiss," Brindle told BBC. This consistent pattern across closely related species points to a shared evolutionary origin. "It's likely that their most recent common ancestor kissed. We think kissing probably evolved around 21.5 million years ago in the large apes."
Connecting Ancient Humans and Neanderthals
The research also examined our ancient relatives, particularly Neanderthals. Earlier DNA analysis revealed that Neanderthals and modern humans shared an oral microbe - a bacterium typically transmitted through saliva. This finding provides compelling evidence that Neanderthals engaged in kissing behaviour long after the evolutionary split from modern humans.
While the study establishes when kissing likely emerged, it doesn't attempt to explain why this behaviour developed. Existing theories remain valid, including suggestions that kissing evolved from grooming practices in early apes or that it served as a health or compatibility check between partners. The new 21-million-year timeline doesn't rule out any of these explanations.
For researchers, the most significant takeaway is that kissing is neither uniquely human nor purely romantic. The behaviour appears repeatedly across diverse species that otherwise share little in common. "It's important for us to understand that this is something we share with our non-human relatives," Brindle emphasized.
She advocates for studying kissing behaviour with the same seriousness as other social interactions, rather than dismissing it due to its association with human relationships. With evidence of similar mouth-to-mouth contact appearing in primates, ancient human relatives, and distant animal groups, researchers argue that kissing may be less of a cultural invention and more of a long-standing social tool deeply embedded in our evolutionary history.
