The origins of kissing Did it really develop from ancient primate grooming behaviour?

We do it sitting in a tree, under the mistletoe, at midnight to ring in the new year. In fairytales, the act transforms frogs into princes and awakens heroines from enchanted slumber. We make up with it, seal with it, and, in Romeo Montague's case at least, die with it.

- Donna Lu

The earliest record of kissing dates back 4,500 years to ancient Mesopotamia (present-day Syria and Iraq), where cuneiform texts suggest smooching formed an ordinary part of romantic intimacy. Millennia later, the exact origins of kissing are still a matter of debate; a new theory proposes that snogging arose from primate grooming behaviour deep in our evolutionary past. How did the behaviour come about?

"Freud, who was famously hung up on childhood complexes, took the view that kissing has something to do with the memory of the pleasures of sucking on your mother's breast," the renowned evolutionary psychologist Prof Robin Dunbar writes in his 2012 book, The Science of Love. "But the argument really doesn't hold water. After all, if it really is a reversion to breast-sucking, why not just do that?"

Others hypothesise that osculation - the act of kissing - may have developed from premastication or "kiss feeding", the act of pre-chewing food and pushing it into an infant's mouth with the tongue.