Neanderthals and Modern Humans Were Likely Kissing, Scientists Suggest

Among Galápagos albatrosses to Arctic mammals, primates to great apes, various animals engage in mouth-to-mouth contact. Currently, scientists suggest that Neanderthals did it too – and possibly locked lips with early Homo sapiens.

Common Microbial Evidence

It is not the first time scientists have proposed ancient relatives and early modern humans were closely connected. In previous studies, researchers have discovered humans and their Neanderthal relatives shared the identical oral bacteria for millions of years after the two species split, suggesting they swapped saliva.

"Likely they were kissing," the researcher noted, explaining that the concept aligned with studies that has revealed humans of certain genetic backgrounds contain Neanderthal DNA in their genetic makeup, demonstrating interbreeding was at play.

Intimate Interpretation

"This offers a different spin on ancient interactions," the lead researcher said.

Publishing in the journal Evolution and Human Behavior, Brindle and colleagues detail how, to investigate the historical roots of intimate contact, they first had to come up with a description that was not limited to how people kiss.

Defining Kissing

"Previously there were some previous attempts to describe a intimate act, but it's largely human-centric, which means that basically other animals don't kiss. Now we understand that they likely engage, it might just not look from what human kissing looks like," explained the evolutionary biologist.

Nonetheless, she said some behaviors that looked like intimate contact were distinct activities – such as the chewing and food sharing, or "kiss-fighting", observed in fish known as French grunts.

As a result the team came up with a definition of kissing based on friendly interactions involving directed mouth-to-mouth contact with a individual of the identical group, with some motion of the mouth but no transfer of nutrition.

Research Approach

The lead researcher said they concentrated on accounts of intimate behavior in non-human species from the African continent and Asian regions, including bonobos, chimpanzees and great apes, and employed digital recordings to verify the reports.

The researchers then combined this information with information on the genetic connections between living and ancient species of such primates.

Evolutionary Timeline

Researchers propose the results suggest kissing evolved approximately 21.5m and 16.9 million years ago in the predecessors of the large apes.

Placement of ancient hominins on this evolutionary lineage means it is probable they, too, indulged in a intimate act, the scientists say. But the behavior may not have been confined to their specific group.

"Reality that modern people engage intimately, the fact that we now have demonstrated that ancient relatives probably engaged, indicates that the both groups are also likely to have engage," the researcher added.

Evolutionary Significance

Although the evolutionary explanation is debated, the expert explained intimate contact could be employed in reproductive situations to possibly enhance reproductive success or assist in selecting between mates, while it might help strengthen connections when practiced in a non-sexual manner.

Another expert in the activities of primates commented that as intimate contact was observed in a broad spectrum of apes it made sense its roots extend far into our ancient history, and an examination of various types of kissing among a broader range of animals might push its beginnings back even earlier still.

"Behaviors that we consider as signatures of human life, like intimate contact, are not exclusive to us if we examine carefully at different species," the expert noted.

Cultural Elements

Another professor explained that kissing had a social component as it was not universal to all societies.

"However, as humans we thrive or fail on the strength of our emotional bonds, and ways of promoting confidence and intimacy will have been important for eons," the professor stated. "This could represent an image that appears a bit contradictory to our incorrect assumptions of a supposedly aggressive and ancient history, but actually it should be expected that ancient hominins – and including Neanderthals and our human ancestors together – engaged intimately."