Neanderthals and Early Humans May Have Engaging in Intimate Contact, Researchers Propose

From Galápagos albatrosses to polar bears, primates to great apes, certain species engage in mouth-to-mouth contact. Currently, scientists suggest that ancient hominins did it too – and might even have exchanged kisses with modern humans.

Shared Microbial Evidence

It is not the first time experts have suggested ancient relatives and early modern humans were intimately acquainted. In previous studies, researchers have discovered humans and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the two species split, implying they exchanged oral fluids.

"Probably they were kissing," she said, adding that the idea chimed with research that has found people of certain genetic backgrounds have bits of ancient genetic material in their genetic makeup, demonstrating genetic mixing was at play.

Romantic Interpretation

"It certainly puts a more romantic perspective on ancient interactions," Brindle commented.

Publishing in the journal Evolution and Human Behavior, Brindle and colleagues report how, to investigate the evolutionary origins of kissing, they first had to develop a definition that was not limited to how humans kiss.

Defining Intimate Contact

"Previously there were some efforts to define a intimate act, but it's largely human-centric, which implies that essentially non-human species don't kiss. Currently we understand that they probably do, it might just not look from what human kissing looks like," said the evolutionary biologist.

Nonetheless, she noted some actions that resembled kissing were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", observed in fish called French grunts.

As a result the research group came up with a description of kissing centered around social behaviors involving intentional mouth-to-mouth contact with a member of the same species, with some movement of the mouth but absence of nutrition.

Research Approach

The lead researcher said they focused on accounts of intimate behavior in primates from the African continent and Asia, including primates, apes and great apes, and employed digital recordings to verify the reports.

Scientists then combined this data with information on the genetic connections between extant and ancient types of such animals.

Historical Origins

The team propose the findings suggest intimate contact evolved approximately 21.5m and 16.9 million years ago in the ancestors of the great primates.

Placement of ancient hominins on this evolutionary lineage suggests it is probable they, too, indulged in a kiss, the scientists say. But the activity might not have been limited to their own species.

"The fact that humans engage intimately, the fact that we now have demonstrated that Neanderthals very likely kissed, suggests that the both groups are probably did engage," the researcher noted.

Evolutionary Importance

Although the evolutionary explanation is discussed, Brindle said kissing could be used in reproductive situations to potentially enhance mating outcomes or assist in selecting between partners, while it could assist strengthen connections when practiced in a non-sexual manner.

Another expert in the behavior of great apes commented that as kissing behavior was observed in a wide range of primates it made sense its origins lie deep in our evolutionary past, and an examination of various types of kissing among a broader range of species might extend its origins back even earlier still.

"Behaviors that we think of as characteristics of human life, like kissing, are not exclusive to us if we look closely at different species," he said.

Social Elements

Another professor said that kissing had a social component as it was not universal to all human groups.

"Nonetheless, as people we thrive or fail on the strength of our emotional bonds, and ways of encouraging confidence and intimacy will have been important for millions of years," she said. "This could represent an image that seems a bit contradictory to our incorrect assumptions of a rather ruthless and aggressive past, but really it ought to be expected that ancient hominins – and even Neanderthals and our own species together – engaged intimately."