Monkeys Were Smooching Long Before Humans Even Existed, Study Says

It turns out the story of the first kiss didn’t begin with humans at all — but with our ancient primate ancestors. A new study by researchers from Oxford University and the Florida Institute of Technology suggests that kissing is far older than previously believed, possibly dating back 20 million years.

According to the team, species like chimpanzees, bonobos, orangutans and gorillas all share the instinct to kiss. This widespread behaviour strongly hints at a deep evolutionary origin. “If so many primates do it, chances are it didn’t start with us,” the researchers noted.

To investigate, scientists analysed decades of primate behavioural research and used evolutionary modelling to trace how far back this intimate act could go. After running millions of simulations, the models placed the earliest form of smooching somewhere between 21.5 and 16.9 million years ago.

The findings, published in Evolution and Human Behaviour, describe kissing in its most practical and unromantic definition: gentle, non-aggressive mouth-to-mouth contact without food exchange. This didn’t necessarily mean romantic affection — it could have been a way to bond with partners, comfort family members, or strengthen social connections within a group.

Interestingly, the researchers found evidence that even Neanderthals and early humans might have kissed. Genetic clues suggest the two species once exchanged mouth microbes — most likely through intimate contact — long before they diverged between 450,000 and 750,000 years ago.

Although scholars still debate the exact reason kissing evolved, one idea is that it helped build trust and maintain complex social relationships. Even today, quick pecks between friends or family members remain a common way to show warmth and familiarity across cultures.

As lead author Dr. Matilda Brindle puts it, “Kissing didn’t simply appear out of nowhere. It’s a behaviour woven deep into primate history — and we’ve simply inherited it.”

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