Ancient Hominins and Early Humans Were Likely Engaging in Intimate Contact, Researchers Propose

Among seabirds to Arctic mammals, chimpanzees to great apes, various animals appear to kiss. Now, scientists propose that Neanderthals did it too – and might even have exchanged kisses with modern humans.

Common Oral Evidence

It is not the first time scientists have proposed ancient relatives and Homo sapiens were closely connected. In previous studies, scientists have discovered humans and their Neanderthal relatives possessed the same mouth microbe for millions of years after the evolutionary divergence, implying they exchanged oral fluids.

"Likely they were kissing," she said, explaining that the idea aligned with research that has revealed people of certain genetic backgrounds contain Neanderthal DNA in their genome, revealing genetic mixing was at play.

Intimate Interpretation

"It certainly puts a different perspective on ancient interactions," the lead researcher commented.

Publishing in the journal a scientific periodical, Brindle and colleagues detail how, to investigate the historical roots of kissing, they first had to develop a definition that was not restricted by how humans kiss.

Defining Kissing

"Previously there were some previous attempts to describe a kiss, but it's largely human-centric, which implies that essentially other animals do not engage in this. Now we know that they probably do, it may appear different from what our intimate contact looks like," explained the evolutionary biologist.

Nonetheless, she noted some actions that looked like kissing were something rather different – such as the processing and transfer of food, or "mouth contact", seen in fish known as French grunts.

As a result the research group came up with a description of intimate contact centered around social behaviors involving intentional mouth-to-mouth contact with a individual of the identical group, with some movement of the mouth but no transfer of food.

Study Approach

The lead researcher said they focused on accounts of intimate behavior in primates from the African continent and Asia, including bonobos, apes and orangutans, and used digital recordings to verify the observations.

The researchers then integrated this data with details on the genetic connections between living and ancient types of such primates.

Evolutionary Origins

The team say the results suggest kissing developed somewhere between 21.5m and 16.9m years ago in the predecessors of the great primates.

Placement of Neanderthals on this family tree means it is likely they, too, indulged in a kiss, the researchers say. But the activity might not have been confined to their specific group.

"The fact that humans kiss, the reality that we currently have shown that Neanderthals very likely kissed, indicates that the two [species] are also likely to have kissed," the researcher added.

Evolutionary Significance

Although the evolutionary explanation is debated, Brindle explained intimate contact could be employed in reproductive situations to possibly enhance mating outcomes or help choose between partners, while it might help strengthen connections when practiced in a platonic way.

A separate researcher 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 evolutionary past, and an examination of different forms of kissing among a wider variety of animals might extend its beginnings back even earlier still.

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

Social Aspects

Another professor explained that intimate contact had a cultural element as it was not universal to all societies.

"Nonetheless, as people we succeed or struggle on the quality of our emotional bonds, and ways of encouraging confidence and intimacy will have been important for millions of years," the professor stated. "It might be an concept that appears a bit contradictory to our incorrect assumptions of a supposedly aggressive and aggressive past, but actually it should be no surprise that ancient hominins – and even Neanderthals and our own species collectively – engaged intimately."