🔗 Share this article

From seabirds to polar bears, chimpanzees to great apes, certain species appear to kiss. Currently, researchers suggest that Neanderthals also engaged in this behavior – and might even have locked lips with modern humans.

Shared Microbial Clues

This isn't the initial instance experts have proposed Neanderthals and Homo sapiens were intimately acquainted. Among earlier research, researchers have found humans and their thick-browed cousins possessed the identical oral bacteria for hundreds of thousands of years after the two species split, suggesting they exchanged oral fluids.

"Likely they were engaging in intimate contact," she said, adding that the concept aligned with studies that has revealed humans of non-African ancestry contain ancient genetic material in their genome, demonstrating interbreeding was occurring.

Romantic Spin

"It certainly puts a more romantic perspective on human-Neanderthal relations," Brindle said.

Publishing in the publication Evolution and Human Behavior, Brindle and colleagues report how, to explore the evolutionary origins of kissing, they first had to come up with a definition that was not limited to how humans smooch.

Defining Kissing

"Previously there were some previous attempts to define a kiss, but it's very much been focused on humans, which means that essentially non-human species don't kiss. Currently we know that they likely engage, it may appear different from what our intimate contact looks like," said Brindle.

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

As a result the team came up with a description of kissing based on friendly interactions involving intentional oral interaction with a individual of the identical group, with some motion of the mouth but absence of nutrition.

Study Approach

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

Scientists then integrated this data with details on the evolutionary relationships between living and extinct species of such primates.

Historical Origins

The team propose the findings suggest kissing evolved somewhere between 21.5 million and 16.9m years ago in the ancestors of the large apes.

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

"Reality that modern people kiss, the fact that we currently have demonstrated that ancient relatives very likely kissed, suggests that the both groups are probably did engage," the researcher added.

Biological Importance

Although the evolutionary explanation is debated, Brindle said kissing could be employed in sexual contexts to possibly enhance mating outcomes or assist in selecting between mates, while it could assist reinforce bonding when used in a platonic way.

A separate researcher in the activities of primates said that as intimate contact was seen in a broad spectrum of primates it made sense its origins lie deep in our ancient history, and an analysis of different forms of intimate behavior among a wider variety of animals might push its origins back further still.

"Behaviors that we consider as signatures of our species, like kissing, are not exclusive to us if we look closely at other animals," the expert noted.

Social Elements

An archaeology expert explained that intimate contact 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 ways of promoting trust and intimacy will have been important for eons," she said. "This could represent an image that appears a bit contradictory to our misplaced ideas of a supposedly aggressive and ancient history, but really it should be no surprise that ancient hominins – and even them and our own species together – kissed."