🔗 Share this article

From seabirds to polar bears, chimpanzees to great apes, certain species engage in mouth-to-mouth contact. Currently, researchers propose that ancient hominins did it too – and might even have exchanged kisses with modern humans.

Common Microbial Evidence

It is not the first time experts have proposed Neanderthals and Homo sapiens were closely connected. In earlier research, scientists have found modern people and their Neanderthal relatives possessed the same mouth microbe for millions of years after the two species split, suggesting they swapped saliva.

"Probably they were kissing," the researcher noted, adding that the idea chimed with studies that has found people of certain genetic backgrounds have bits of Neanderthal DNA in their genetic makeup, demonstrating interbreeding was at play.

Romantic Interpretation

"It certainly puts a more romantic perspective on human-Neanderthal relations," the lead researcher said.

Publishing in the publication Evolution and Human Behavior, the researcher and her team report how, to investigate the historical roots of intimate contact, they first had to develop a definition that was not limited to how people smooch.

Describing Kissing

"Previously there were some previous attempts to describe a kiss, but it's largely human-centric, which means that essentially other animals don't kiss. Currently we understand that they likely engage, it may appear different from what human kissing looks like," explained the evolutionary biologist.

However, she noted some behaviors that looked like intimate contact were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", observed in aquatic species known as certain marine animals.

As a result the team developed a definition of kissing centered around friendly interactions involving directed oral interaction with a member of the identical group, with some movement of the oral area but absence of food.

Research Approach

Brindle said they focused on reports of intimate behavior in primates from Africa and Asia, including primates, chimpanzees and great apes, and employed digital recordings to verify the observations.

Scientists then combined this information with details on the genetic connections between living and ancient types of such primates.

Historical Origins

Researchers propose the results suggest kissing evolved somewhere between 21.5m and 16.9m years ago in the ancestors of the great primates.

The position of Neanderthals on this family tree suggests it is likely they, too, indulged in a intimate act, the researchers conclude. But the activity may not have been confined to their own species.

"The fact that humans kiss, the reality that we currently have shown that Neanderthals probably kissed, indicates that the both groups are also likely to have kissed," Brindle noted.

Biological Significance

Although the evolutionary explanation is debated, the expert said kissing could be employed in reproductive situations to potentially increase mating outcomes or help choose between partners, while it might help reinforce bonding when practiced in a platonic way.

Another expert in the behavior of primates commented that as kissing behavior was seen in a wide range of primates it made sense its roots lie deep in our ancient history, and an analysis of various types of intimate behavior among a wider variety of animals might extend its beginnings back further still.

"Things that we think of as characteristics of our species, like intimate contact, are not exclusive to us if we look closely at different species," he said.

Social Aspects

An archaeology expert said that kissing had a cultural element as it was not universal to all human groups.

"Nonetheless, as humans we thrive or fail on the strength of our relationships, and methods of encouraging trust and intimacy will have been important for eons," the professor stated. "This could represent an image that appears a bit incongruous to our incorrect assumptions of a rather ruthless and aggressive past, but actually it should be no surprise that ancient hominins – and even Neanderthals and our own species collectively – kissed."