🔗 Share this article

From seabirds to Arctic mammals, primates to great apes, various animals appear to kiss. Currently, scientists propose that Neanderthals also engaged in this behavior – and might even have locked lips with modern humans.

Shared Oral Evidence

This isn't the initial instance scientists have suggested Neanderthals and Homo sapiens were closely connected. Among previous studies, researchers have found humans and their thick-browed cousins shared the identical oral bacteria for hundreds of thousands of years after the two species split, implying they exchanged oral fluids.

"Likely they were kissing," the researcher noted, adding that the idea aligned with research that has revealed humans of non-African ancestry have bits of Neanderthal DNA in their genome, demonstrating interbreeding was occurring.

Romantic Interpretation

"This offers a different perspective on ancient interactions," Brindle commented.

Writing in the journal Evolution and Human Behavior, Brindle and colleagues report how, to explore the evolutionary origins of intimate contact, they first had to develop a description that was not restricted by how people kiss.

Defining Intimate Contact

"Previously there were some previous attempts to describe a kiss, but it's very much been focused on humans, which means that basically other animals don't kiss. Currently we know that they probably do, it may appear different from what human kissing resembles," explained the evolutionary biologist.

Nonetheless, she said some actions that resembled intimate contact were distinct activities – such as the processing and food sharing, or "kiss-fighting", observed in aquatic species known as French grunts.

Consequently the research group came up with a definition of kissing based on friendly interactions involving intentional mouth-to-mouth contact with a member of the identical group, with some motion of the oral area but no transfer of nutrition.

Study Methods

Brindle explained they focused on accounts of kissing in primates from Africa and Asian regions, including primates, apes and great apes, and used online videos to verify the observations.

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

Evolutionary Timeline

Researchers propose the findings indicate intimate contact evolved somewhere between 21.5m and 16.9 million years ago in the predecessors of the great primates.

Placement of Neanderthals on this family tree suggests it is probable they, too, indulged in a intimate act, the scientists say. But the behavior might not have been confined to their own species.

"Reality that humans engage intimately, the fact that we currently have shown that ancient relatives probably kissed, suggests that the both groups are probably did kissed," the researcher noted.

Biological Significance

Although the scientific reasoning is discussed, Brindle explained kissing could be used in sexual contexts to potentially enhance reproductive success or help choose between mates, while it might help strengthen connections when practiced in a non-sexual manner.

A separate researcher in the behavior of primates commented that as intimate contact was observed in a broad spectrum of apes it was logical its roots lie deep in our ancient history, and an analysis of various types of kissing among a broader range of species might extend its origins back further still.

"Behaviors that we think of as signatures of our species, like kissing, are not exclusive to us if we look closely at different species," he said.

Cultural Elements

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

"However, as people we thrive or fail on the quality of our relationships, and ways of promoting trust and intimacy will have been significant for millions of years," she said. "This could represent an concept that appears a bit contradictory to our incorrect assumptions of a rather ruthless and aggressive past, but actually it ought to be expected that ancient hominins – and including them and our human ancestors collectively – engaged intimately."