🔗 Share this article

From seabirds to polar bears, primates to orangutans, various animals engage in mouth-to-mouth contact. Now, researchers suggest that Neanderthals did it too – and possibly locked lips with early Homo sapiens.

Shared Microbial Evidence

This isn't the initial instance scientists have suggested Neanderthals and early modern humans were intimately acquainted. In previous studies, researchers have found humans 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," the researcher noted, adding that the concept aligned with studies that has revealed people of certain genetic backgrounds contain ancient genetic material in their genome, demonstrating genetic mixing was occurring.

Romantic Spin

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

Writing in the publication a scientific periodical, Brindle and colleagues report how, to investigate the evolutionary origins of kissing, they first had to develop a description that was not limited to how humans smooch.

Describing Intimate Contact

"There have been some efforts to define a intimate act, but it's very much been focused on humans, which implies that basically other animals don't kiss. Currently we understand that they likely engage, it may appear different from what human kissing resembles," said Brindle.

Nonetheless, she noted some actions that resembled kissing were something rather different – such as the processing and transfer of food, or "mouth contact", seen in fish known as certain marine animals.

Consequently the team came up with a definition of kissing centered around friendly interactions involving intentional oral interaction with a member of the identical group, with some motion of the mouth but absence of food.

Study Approach

Brindle explained they focused on reports of intimate behavior in non-human species from Africa and Asia, including primates, apes and orangutans, and used digital recordings to confirm the observations.

The researchers then combined this information with details on the genetic connections between living and ancient types of such primates.

Historical Origins

The team propose the results suggest intimate contact developed somewhere between 21.5 million and 16.9 million years ago in the ancestors of the large apes.

Placement of ancient hominins on this family tree means it is likely they, too, indulged in a intimate act, the researchers say. But the behavior may not have been confined to their specific group.

"Reality that modern people kiss, the fact that we now have demonstrated that Neanderthals probably kissed, indicates that the two [species] are also likely to have engage," Brindle noted.

Biological Significance

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

Another expert in the activities of primates commented that as intimate contact was observed in a broad spectrum of apes 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 beginnings back even earlier still.

"Behaviors that we think of as characteristics of our species, like kissing, are not unique to us if we examine carefully 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 human groups.

"Nonetheless, as humans we thrive or fail on the quality of our emotional bonds, and ways of promoting trust and intimacy will have been significant for millions of years," she said. "It might be an concept that seems a bit contradictory to our incorrect assumptions of a rather ruthless and aggressive past, but really it ought to be expected that Neanderthals – and including Neanderthals and our human ancestors collectively – engaged intimately."