Scientists Trace First Kiss to Early Primates

Study suggests kissing began 20 million years ago

A new study has concluded that kissing predates humans and likely originated with the primate ancestors of great apes around 20 million years ago. Researchers from Oxford University and the Florida Institute of Technology examined the evolutionary roots of kissing, noting that it offers no clear survival benefit and can even spread disease. Despite this, humans, chimpanzees, bonobos, orangutans, and gorillas all engage in kissing, pointing to a shared ancestral behavior. By combining observations of primate interactions with evolutionary data, scientists attempted to estimate when the practice first appeared.

Dating the First Kiss

Lead author Dr. Matilda Brindle explained that the team used modeling approaches to simulate evolutionary scenarios. Millions of simulations placed the origin of kissing between 21.5 and 16.9 million years ago. The findings were published in the journal Evolution and Human Behavior. Researchers defined kissing as non-aggressive, mouth-to-mouth contact without food transfer, encompassing both sexual and platonic forms.

This definition allowed scientists to include affectionate gestures between family members and friendly greetings. The study acknowledged that the reasons for kissing’s persistence remain debated. Some theories suggest sexual kissing helps assess mate suitability, while others argue it functions as foreplay to increase chances of fertilization. Platonic kisses may serve to strengthen social bonds and manage complex group dynamics.

Evolutionary Significance

The research highlighted that Neanderthals and humans likely shared the practice of kissing. Evidence of interbreeding and the exchange of oral microbes suggests saliva-swapping occurred long after the two species diverged 450,000 to 750,000 years ago. Such findings indicate that kissing may have played a role in social and reproductive interactions across species. The persistence of the behavior underscores its importance beyond mere affection.

Scientists continue to debate why kissing endured despite potential health risks. Theories range from its role in mate selection to its function in reinforcing social ties. The study emphasizes that kissing is not unique to humans but part of a broader evolutionary heritage. This perspective reframes the act as a deeply rooted behavior rather than a cultural invention.

Broader Implications

Understanding the evolutionary origins of kissing sheds light on how social behaviors develop and persist. It also highlights the role of non-verbal communication in maintaining relationships across species. The findings suggest that behaviors often considered cultural may have ancient biological foundations. Kissing, therefore, represents both a social tool and an evolutionary legacy.