New research indicates that the act of kissing may date back over 20 million years, predating the existence of modern humans. A team of scientists from Oxford University in England conducted an extensive review of primate studies to uncover the evolutionary history of this behavior. Their findings, published in the journal Evolution and Human Behavior, suggest that kissing likely originated from an ancient ancestor of present-day apes, engaging in mouth-to-mouth contact between approximately 16.9 million and 21.5 million years ago.
The research team, led by evolutionary biologist Matilda Brindle, utilized statistical modeling to analyze the kissing behaviors of various primate species, including chimpanzees, bonobos, orangutans, and gorillas. Brindle described kissing as an “evolutionary conundrum,” noting that while it is prevalent among primates, it poses risks such as germ transmission and does not appear to directly enhance survival.
Understanding the origins of kissing is complex, as the behavior itself is not preserved in the fossil record. Consequently, researchers rely on living primates to glean insights about their ancestors. Notably, the oldest written references to human kissing can be traced back approximately 4,500 years to ancient civilizations in Mesopotamia and Egypt. Despite its long history, a 2015 study revealed that only 46% of humans engage in kissing.
Brindle emphasized that the evolutionary significance of kissing does not guarantee its retention across species. “We found a strong evolutionary signal in kissing, but it doesn’t mean it has to be retained,” she explained. Primate species exhibit remarkable adaptability and intelligence, suggesting that while kissing may be advantageous in certain contexts, it can also carry significant health risks.
To solidify their findings, the research team conducted over 10 million simulations to assess the likelihood of early ape ancestors kissing. The results strongly support the notion that extinct relatives, such as Neanderthals, likely engaged in similar behaviors alongside early humans. Nevertheless, Brindle noted that the model does not clarify the original purpose of kissing or how it has transformed over time. Much of the data comes from primates in captivity, highlighting the need for further research on wild populations.
Experts acknowledge that this study provides a foundation for future investigations. Justin Garcia, director of The Kinsey Institute at Indiana University, remarked in an email to CNN, “This is a wonderful example of the interplay of nature and nurture, including for a behavior many of us humans consider so deeply intimate.” He highlighted that kissing is both a biological and cultural phenomenon, invoking bodily senses while also varying across individuals and populations.
The research not only deepens our understanding of kissing’s evolutionary context but also invites further inquiry into the interplay of genetics and culture in shaping human behaviors. As scientists continue to explore these connections, the origins of this seemingly simple act may reveal more about the intricate tapestry of our evolutionary history.
