Neanderthals and Modern Humans Were Likely Kissing, Researchers Propose

Among seabirds to Arctic mammals, primates to great apes, various animals appear to kiss. Currently, scientists propose that ancient hominins also engaged in this behavior – and might even have exchanged kisses with modern humans.

Shared Oral Clues

It is not the first time scientists have suggested ancient relatives and Homo sapiens were closely connected. In earlier research, scientists have found modern people and their thick-browed cousins shared the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Probably they were engaging in intimate contact," she said, explaining that the concept aligned with studies that has found humans of certain genetic backgrounds contain ancient genetic material in their genome, demonstrating genetic mixing was at play.

Intimate Spin

"It certainly puts a different spin on human-Neanderthal relations," the lead researcher said.

Writing in the journal a scientific periodical, the researcher and colleagues detail how, to explore the historical roots of intimate contact, they first had to develop a description that was not restricted by how humans smooch.

Defining Intimate Contact

"Previously there were some efforts to define a kiss, but it's very much been human-centric, which means that essentially other animals don't kiss. Now we know that they probably do, it might just not look from what our intimate contact looks like," said the evolutionary biologist.

However, she said some actions that looked like kissing were something rather different – such as the processing and transfer of food, or "mouth contact", observed in fish called certain marine animals.

Consequently the team came up with a description of intimate contact based on social behaviors involving directed mouth-to-mouth contact with a member of the same species, with some movement of the mouth but no transfer of nutrition.

Study Approach

Brindle explained they concentrated on accounts of kissing in primates from the African continent and Asian regions, including bonobos, chimpanzees and great apes, and employed online videos to confirm the observations.

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

Evolutionary Origins

Researchers propose the findings indicate kissing evolved somewhere between 21.5m and 16.9m years ago in the ancestors of the large apes.

Placement of ancient hominins on this family tree means it is probable they, too, engaged in a kiss, the researchers say. But the activity may not have been limited to their specific group.

"The fact that humans engage intimately, the fact that we currently have shown that ancient relatives probably kissed, suggests that the two [species] are probably did kissed," Brindle added.

Evolutionary Significance

Although the scientific reasoning is debated, the expert explained kissing could be employed in sexual contexts to possibly enhance mating outcomes or help choose between partners, while it could assist reinforce bonding when used in a platonic way.

Another expert in the behavior of great apes said that as kissing behavior was seen in a wide range of apes it was logical its origins lie deep in our ancient history, and an analysis of various types of intimate behavior among a broader range of animals might extend its beginnings back further still.

"Things 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.

Cultural Elements

An archaeology expert explained that intimate contact had a social component as it was not common to all human groups.

"Nonetheless, as humans we succeed or struggle on the quality of our relationships, and methods of promoting trust and intimacy will have been important for eons," she said. "This could represent an image that seems a bit incongruous to our misplaced ideas of a supposedly aggressive and ancient history, but really it ought to be no surprise that Neanderthals – and even Neanderthals and our human ancestors collectively – engaged intimately."