New research has fundamentally reshaped the understanding of kissing, suggesting the intimate act predates humanity by millions of years and has deep roots in primate evolution rather than originating as a romantic human custom.
A new study by researchers at the University of Oxford and the Florida Institute of Technology indicates that mouth-to-mouth contact, defined as non-aggressive and non-feeding, likely first occurred between 21.5 and 16.9 million years ago. This pushes back the estimated origin of kissing by tens of millions of years.
The findings, published in the journal Evolution and Human Behaviour, challenge the traditional view that kissing is a behavior unique to human courtship.
The research examined various primate species, including humans, chimpanzees, bonobos, orangutans, and gorillas, all of which exhibit some form of mouth-to-mouth contact. The scientists concluded that this shared behavior was inherited from a common ancestor.
Dr. Matilda Brindle, the lead author from Oxford’s Department of Biology, explained that the team used multiple evolutionary simulation models. These models were run millions of times to predict the timeframe when the behavior first emerged.
While "kissing" in this context encompasses both romantic gestures and friendly or familial expressions, its evolutionary purpose remains a subject of debate.
Scientists hypothesize that romantic kissing might serve to assess a potential mate’s quality or to enhance the chances of conception by stimulating sexual arousal. Friendly or familial kissing, by contrast, could play a role in building social bonds and managing complex relationships within groups.
The study also suggests that modern humans and Neanderthals likely engaged in kissing. Evidence points to interbreeding between the two species and shared oral microbes, indicating an exchange of saliva.
Modern humans and Neanderthals diverged between 450,000 and 750,000 years ago, according to previous research.