Neanderthals and Modern Humans Were Likely Engaging in Intimate Contact, Scientists Suggest

Among Galápagos albatrosses to polar bears, primates to orangutans, certain species appear to kiss. Now, researchers propose that ancient hominins did it too – and might even have exchanged kisses with modern humans.

Shared Microbial Evidence

This isn't the initial instance experts have proposed Neanderthals and Homo sapiens were closely connected. Among earlier research, scientists have found humans and their thick-browed cousins possessed the same mouth microbe for millions of years after the evolutionary divergence, suggesting they swapped saliva.

"Likely they were engaging in intimate contact," the researcher noted, adding that the concept chimed with studies that has revealed humans of certain genetic backgrounds contain ancient genetic material in their genome, revealing interbreeding was occurring.

Romantic Spin

"This offers a more romantic perspective on ancient interactions," Brindle said.

Writing in the journal a scientific periodical, Brindle and her team detail how, to investigate the evolutionary origins of intimate contact, they first had to come up with a definition that was not limited to how people smooch.

Defining Intimate Contact

"Previously there were some previous attempts to describe a intimate act, but it's very much been human-centric, which implies that essentially non-human species don't kiss. Currently we understand that they likely engage, it may appear different from what our intimate contact looks like," explained the evolutionary biologist.

Nonetheless, she said some actions that resembled intimate contact were something rather different – such as the chewing and transfer of food, or "mouth contact", observed in aquatic species known as certain marine animals.

Consequently the research group developed a description of intimate contact based on social behaviors involving directed oral interaction with a member of the identical group, with some movement of the mouth but no transfer of food.

Study Approach

The lead researcher said they concentrated on reports of kissing in non-human species from Africa and Asia, including primates, chimpanzees and great apes, and used online videos to confirm the reports.

The researchers then integrated this information with details on the evolutionary relationships between living and ancient types of such primates.

Historical Origins

The team propose the results indicate intimate contact evolved somewhere between 21.5m and 16.9m years ago in the predecessors of the large apes.

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

"Reality that humans kiss, the reality that we now have shown that ancient relatives very likely kissed, suggests that the two [species] are probably did kissed," the researcher noted.

Biological Importance

While the scientific reasoning is discussed, the expert said kissing could be used in sexual contexts to possibly enhance mating outcomes or assist in selecting between mates, while it could assist reinforce bonding when practiced in a platonic way.

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 roots lie deep in our evolutionary past, and an examination of various types of kissing among a broader range of species might extend its beginnings back further still.

"Behaviors that we think of as signatures of human life, like intimate contact, are not unique to us if we look closely at different species," he said.

Social Elements

An archaeology expert 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 relationships, and ways of promoting confidence and intimacy will have been important for eons," she said. "This could represent an concept that seems a bit incongruous to our misplaced ideas of a rather ruthless and ancient history, but actually it ought to be expected that ancient hominins – and even them and our own species collectively – kissed."