🔗 Share this article

From Galápagos albatrosses to polar bears, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Now, researchers suggest that Neanderthals also engaged in this behavior – and might even have locked lips with early Homo sapiens.

Common Oral Clues

This isn't the initial instance scientists have suggested ancient relatives and early modern humans were closely connected. Among earlier research, researchers have discovered humans and their Neanderthal relatives possessed the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Likely they were engaging in intimate contact," the researcher noted, adding that the idea chimed with studies that has revealed humans of certain genetic backgrounds have bits of Neanderthal DNA in their genome, demonstrating interbreeding was at play.

Intimate Interpretation

"This offers a different spin on ancient interactions," Brindle said.

Writing in the journal a scientific periodical, Brindle and colleagues detail how, to investigate the historical roots of intimate contact, they first had to develop a definition that was not restricted by how people kiss.

Defining Kissing

"Previously there were some previous attempts to describe a kiss, but it's very much been human-centric, which implies that basically non-human species don't kiss. Currently we understand that they likely engage, it may appear different from what human kissing resembles," said Brindle.

However, she said some actions that looked like intimate contact were distinct activities – such as the processing and transfer of food, or "kiss-fighting", observed in fish called French grunts.

Consequently the team developed a description of kissing based on friendly interactions involving directed mouth-to-mouth contact with a member of the same species, with some movement of the mouth but absence of nutrition.

Study Approach

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

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

Historical Origins

Researchers propose the findings suggest intimate contact developed approximately 21.5 million and 16.9m years ago in the predecessors of the large apes.

Placement of Neanderthals on this family tree suggests it is probable they, too, indulged in a kiss, the researchers say. But the activity might not have been limited to their specific group.

"The fact that humans engage intimately, the fact that we now have demonstrated that ancient relatives very likely engaged, suggests that the both groups are probably did engage," Brindle added.

Biological Significance

While the evolutionary explanation is discussed, the expert said kissing could be employed in sexual contexts to possibly enhance mating outcomes or help choose between mates, while it might help strengthen connections when used in a non-sexual manner.

A separate researcher in the activities of primates commented that as kissing behavior was seen in a broad spectrum of primates it made sense its origins lie deep in our evolutionary past, and an examination of different forms of kissing among a broader range of species 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 cultural element as it was not universal to all societies.

"However, as humans we succeed or struggle on the quality of our relationships, and methods of promoting confidence and intimacy will have been significant for millions of years," the professor stated. "This could represent an image that seems a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but actually it should be no surprise that Neanderthals – and including them and our human ancestors collectively – kissed."