First kiss dates back 21 million years, say scientists

People, monkeys, even polar bears do this. And now researchers have reconstructed the evolutionary origins of kissing.

Their research suggests that mouth-to-mouth kissing originated more than 21 million years ago and was something that the common ancestors of humans and other great apes were likely into.

The same study concluded that Neanderthals may have kissed too, and humans and Neanderthals may have even kissed each other.

Scientists have studied kissing because it poses something of an evolutionary mystery: it has no obvious advantage for survival or reproduction, and yet the phenomenon is observed not only in many human societies, but throughout the animal kingdom.

By finding evidence of other animals kissing, scientists were able to construct an “evolutionary family tree” to determine when it most likely evolved.

To ensure that they were comparing the same behavior across species, the researchers had to give a very precise – rather unromantic – definition of “kissing.”

In his study published in the journal Evolution and Human Behavior.They defined kissing as non-aggressive, directed oral-to-oral contact “with some movement of the lips or mouthparts and no transfer of food.”

“Humans, chimpanzees and bonobos kiss,” explained lead researcher Dr Matilda Brindle, an evolutionary biologist at the University of Oxford. From this she concluded: “It is likely that their last common ancestor kissed.”

“We think kissing probably evolved in great apes about 21.5 million years ago.”

In this study, scientists found behavior that fits their scientific definition of kissing in wolves, prairie dogs, polar bears (very casually – lots of tongue), and even albatrosses.

They focused on primates, particularly apes, to build an evolutionary picture of the origins of human kissing.

The same study also concluded that Neanderthals – our closest ancient human relatives who went extinct about 40,000 years ago – also kissed.

One previous part of Neanderthal DNA research also showed that modern humans and Neanderthals shared an oral microbe, a type of bacteria found in our saliva.

“This means they must have been exchanging saliva for hundreds of thousands of years after the two species split,” Dr Brindle explained.

While this study determined when kissing evolved, it couldn't answer the question of why.

There are already a number of theories about what it is arose from grooming behavior in our ape ancestors or what an intimate way it might provide assess health and even compatibility partner.

Dr Brindle hopes this will open up the possibility of answering this question.

“It’s important for us to understand that this is something we share with our non-human relatives,” she said.

“We need to study this behavior and not just dismiss it as stupid because it has romantic overtones in people.”