"What’s In A Kiss? 21 Million Years Of Evolution"

"How far back in evolutionary history does kissing go?

Through phylogenetic analysis, an international team of scientists found that kissing was likely present in the ancestor of all apes – which lived 21 million years ago.

Their recent study was published in the journal Evolution and Human Behavior. It defines kissing as nonaggressive mouth-to-mouth contact that does not involve passing food. Many animals kiss, especially primates.

"If you think about the fact that humans and our closest living relatives, chimpanzees and bonobos all kiss, it makes sense that the common ancestor of those three species kisses as well," says Matilda Brindle, lead author and an evolutionary biologist at the University of Oxford."

Emily Kwong, Regina G. Barber, Scott Detrow, Berly McCoy, Kai McNamee, Rebecca Ramirez, and Christopher Intagliata report for NPR November 28, 2025.