Scientists now say the first kiss occurred around 20 million years ago, long before humans evolved, among the primate ancestors of great apes. Researchers from Oxford University and the Florida Institute of Technology combined observations of primate behavior with evolutionary data to estimate when kissing first appeared.
By running millions of simulations, the team concluded that kissing likely emerged between 16.9 and 21.5 million years ago. Their definition of kissing includes any non-aggressive, mouth-to-mouth contact, whether sexual or platonic, such as family greetings or friendly pecks.
The study suggests kissing may have evolved as a way to assess mate suitability, boost sexual arousal, or strengthen social bonds. Evidence also points to Neanderthals and humans exchanging kisses, as shared oral microbes indicate saliva transfer tens of thousands of years ago.
The findings appear in the journal Evolution and Human Behavior.