🔗 Share this article

From seabirds to polar bears, primates to orangutans, various animals appear to kiss. Currently, researchers propose that ancient hominins also engaged in this behavior – and might even have exchanged kisses with early Homo sapiens.

Common Microbial Evidence

It is not the first time experts have suggested ancient relatives and Homo sapiens were intimately acquainted. In earlier research, researchers have discovered humans and their Neanderthal relatives shared the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Probably they were kissing," she said, explaining that the concept chimed with studies that has found people of non-African ancestry contain ancient genetic material in their genetic makeup, demonstrating interbreeding was occurring.

Intimate Interpretation

"This offers a more romantic spin on human-Neanderthal relations," Brindle said.

Publishing in the publication Evolution and Human Behavior, 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 restricted by how people smooch.

Defining Kissing

"Previously there were some efforts to define a kiss, but it's very much been focused on humans, which implies that basically other animals don't kiss. Now we know that they probably do, it may appear different from what our intimate contact looks like," explained the evolutionary biologist.

However, she said some actions that resembled intimate contact were something rather different – such as the processing and food sharing, or "mouth contact", observed in fish known as French grunts.

As a result the team came up with a definition of kissing based on social behaviors involving intentional mouth-to-mouth contact with a individual of the same species, with some movement of the mouth but absence of nutrition.

Research Approach

Brindle said they focused on accounts of intimate behavior in primates from the African continent and Asia, including bonobos, apes and orangutans, and used online videos to verify the observations.

Scientists then integrated this information with information on the genetic connections between living and extinct types of such primates.

Historical Timeline

The team propose the results indicate intimate contact evolved approximately 21.5m and 16.9m years ago in the predecessors of the great primates.

The position of Neanderthals on this evolutionary lineage suggests it is likely they, too, engaged in a intimate act, the scientists say. But the activity might not have been limited to their own species.

"The fact that humans kiss, the reality that we now have demonstrated that Neanderthals probably engaged, indicates that the both groups are probably did kissed," the researcher noted.

Biological Significance

While the scientific reasoning is discussed, Brindle said intimate contact could be employed in sexual contexts to possibly increase reproductive success or help choose between partners, while it could assist reinforce bonding when used in a non-sexual manner.

A separate researcher in the activities of primates said that as intimate contact was observed in a broad spectrum of apes it was logical its origins extend far into our ancient history, and an analysis of various types of kissing among a broader range of animals might extend its beginnings back further still.

"Behaviors that we consider as characteristics of human life, like intimate contact, are not unique to us if we look closely at different species," the expert noted.

Cultural Elements

An archaeology expert said that kissing had a cultural element as it was not universal to all societies.

"Nonetheless, as people we thrive or fail on the strength of our emotional bonds, and methods of encouraging confidence and intimacy will have been significant 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 should be expected that Neanderthals – and including them and our own species collectively – kissed."