First kiss may date back 21 million years, scientists say

Kissing may not be a recent romance after all. A new study published in Evolution and Human Behavior suggests that the mouth-to-mouth gesture originated around 21 million years ago, in the common ancestor we share with great apes long before modern humans existed. The research marks the first attempt to map how kissing evolved across primates, and it challenges the idea that the gesture is purely cultural.

In the wild and in captivity, chimpanzees, bonobos, and orangutans have been observed kissing as part of social bonding, and there are hints that Neanderthals also engaged in the act. One line of evidence points to early Homo sapiens and Neanderthals sharing the same oral bacteria, implying close contact of mouths for hundreds of thousands of years after their split. The researchers behind the study emphasize that such close mouth-to-mouth contact is much older than previously thought and may have played a role in social cohesion long before humans walked upright.

The scientists, including Dr Matilda Brindle of the University of Oxford, conducted cross-species comparisons to trace the behavior back to deep evolutionary roots. Previously, many scholars believed romantic kissing emerged much later, with human cultures documenting lip-to-lip contact primarily in the last several thousand years. While Mesopotamian and Egyptian records show early mentions of kissing around 4,500 years ago, the new work pushes the origin of kissing back into primate history and across multiple species.

The finding suggests kissing may have started as a way to navigate social relationships or exchange information via saliva, and over time it evolved into a complex social gesture linked to bonding and mate choice. For today’s readers, it’s a reminder that everyday gestures have deep, ancient roots that predate humanity as we know it.

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