What exactly counts as a kiss? Study reveals kissing goes back 21 million years, to common ancestor of humans; researchers explain evolution of kissing

A recent study suggests kissing originated approximately 21 million years ago, predating modern humans and possibly emerging from a shared ancestor with other large apes. Researchers defined kissing as non-aggressive mouth-to-mouth contact without food transfer, observing it in various primates. This behavior may have evolved from mothers pre-chewing food for infants.