Kissing, a behavior often associated with romance and intimacy, may have deeper evolutionary roots than previously thought. New research suggests that the practice could trace back as far as 21 million years, originating in an ancient ape ancestor. While historical records indicate kissing in ancient civilizations like Mesopotamia and Egypt around 4,500 years ago, the behavior’s prevalence across only roughly 46% of human cultures has led some to believe it is a relatively recent cultural invention. However, mounting evidence suggests otherwise.
The Case for Ancient Kissing
Observations of modern apes – chimpanzees, bonobos, and orangutans – engaging in lip-to-lip contact, combined with findings of oral bacteria exchange between Neanderthals and Homo sapiens, raise the possibility that kissing predates written history. Researchers led by Matilda Brindle at the University of Oxford set out to investigate this possibility by defining kissing as non-antagonistic mouth-to-mouth contact involving lip movement, excluding activities like food transfer.
Using a rigorous statistical approach called Bayesian modeling, the team mapped kissing behavior across a primate family tree, simulating 10 million evolutionary scenarios. The results suggest that kissing likely evolved in ancestral apes between 21.5 and 16.9 million years ago, with an 84% probability that Neanderthals also practiced it.
“Obviously, that’s just Neanderthals kissing; we don’t know who they’re kissing,” says Brindle. “But together with the evidence that humans and Neanderthals had a similar oral microbiome and that most humans of non-African descent have some Neanderthal DNA, we would argue they were probably kissing each other, which definitely puts a much more romantic spin on human-Neanderthal relations.”
Why Did Kissing Evolve?
The exact reasons behind the evolution of kissing remain unclear, but two leading hypotheses exist. One suggests that kissing may have served as a way for animals to assess mate quality. Bad breath, for instance, could have been a signal to avoid reproduction with an unhealthy partner. Another theory proposes that kissing originated from grooming behaviors and developed to strengthen social bonds and reduce tension – similar to how chimpanzees “kiss and make up” after conflicts.
Nature vs. Culture
While the evidence supports an evolutionary origin for kissing, cultural influences undoubtedly play a role. The practice isn’t universal among human societies, suggesting it may have been adopted or abandoned based on cultural preferences over time. Despite this, the research indicates that kissing is not merely a modern invention, but rather a deeply ingrained behavior with ancient roots.
The findings offer a new perspective on our shared evolutionary history, suggesting that even the most intimate behaviors may have been shaped by millions of years of natural selection.
