Neanderthals and Modern Humans Were Likely Engaging in Intimate Contact, Researchers Propose

Among seabirds to Arctic mammals, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Currently, scientists propose that ancient hominins did it too – and might even have locked lips with early Homo sapiens.

Common Oral Evidence

It is not the first time experts have proposed Neanderthals and Homo sapiens were intimately acquainted. Among earlier research, researchers have found humans and their Neanderthal relatives shared the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, implying they exchanged oral fluids.

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

Intimate Spin

"This offers a more romantic perspective on human-Neanderthal relations," Brindle commented.

Writing in the publication a scientific periodical, Brindle and her team detail how, to investigate the historical roots of intimate contact, they first had to develop a definition that was not limited to how people smooch.

Defining Kissing

"Previously there were some previous attempts to describe a kiss, but it's very much been focused on humans, which implies that essentially other animals don't kiss. Now we know that they likely engage, it may appear different from what our intimate contact looks like," explained Brindle.

Nonetheless, she said some behaviors that looked like intimate contact were distinct activities – such as the chewing and transfer of food, or "mouth contact", seen in aquatic species known as French grunts.

As a result the research group developed a definition of intimate contact centered around social behaviors involving intentional mouth-to-mouth contact with a individual of the identical group, with some motion of the oral area but no transfer of food.

Study Approach

The lead researcher explained they focused on accounts of intimate behavior in primates from Africa and Asian regions, including primates, chimpanzees and great apes, and used online videos to verify the observations.

The researchers then combined this data with details on the evolutionary relationships between extant and extinct species of such primates.

Evolutionary Timeline

Researchers say the findings suggest kissing developed approximately 21.5 million and 16.9 million years ago in the predecessors of the great primates.

The position of Neanderthals on this family tree means it is likely they, too, indulged in a kiss, the scientists say. But the activity might not have been limited to their own species.

"The fact that modern people kiss, the fact that we currently have demonstrated that ancient relatives very likely kissed, indicates that the two [species] are also likely to have kissed," the researcher noted.

Biological Importance

While the evolutionary explanation is debated, the expert said intimate contact could be employed in sexual contexts to possibly increase mating outcomes or help choose between partners, while it could assist reinforce bonding when used in a platonic way.

A separate researcher in the activities of great apes commented that as intimate contact was observed in a broad spectrum of apes it made sense its origins lie deep in our ancient history, and an examination of different forms of kissing among a wider variety of species might push its beginnings back even earlier still.

"Behaviors that we consider as characteristics of human life, like intimate contact, are not unique to us if we examine carefully at different species," he said.

Social Elements

An archaeology expert said that kissing had a social component as it was not common to all human groups.

"However, as people we succeed or struggle on the quality of our relationships, and ways of promoting trust and intimacy will have been important for eons," she said. "It might be an image that seems a bit contradictory to our misplaced ideas of a rather ruthless and aggressive past, but really it should be no surprise that Neanderthals – and even Neanderthals and our own species collectively – kissed."