🔗 Share this article

Among Galápagos albatrosses to Arctic mammals, primates to orangutans, certain species engage in mouth-to-mouth contact. Now, scientists propose that Neanderthals also engaged in this behavior – and possibly exchanged kisses with modern humans.

Shared Oral Evidence

This isn't the initial instance scientists have suggested ancient relatives and Homo sapiens were closely connected. Among earlier research, researchers have discovered modern people and their thick-browed cousins shared the same mouth microbe for hundreds of thousands of years after the two species split, implying they exchanged oral fluids.

"Likely they were kissing," she said, adding that the concept chimed with research that has found humans of non-African ancestry have bits of ancient genetic material in their genome, revealing genetic mixing was occurring.

Intimate Interpretation

"This offers a more romantic perspective on human-Neanderthal relations," the lead researcher said.

Writing in the publication a scientific periodical, Brindle and her team detail how, to investigate the evolutionary origins of kissing, they first had to come up with a definition that was not restricted by how people kiss.

Defining Kissing

"Previously there were some efforts to define a kiss, but it's very much been human-centric, which implies that basically non-human species don't kiss. Now we know that they likely engage, it might just not look from what our intimate contact resembles," explained the evolutionary biologist.

However, she said some actions that resembled intimate contact were distinct activities – such as the chewing and food sharing, or "kiss-fighting", seen in aquatic species called French grunts.

Consequently the research group developed a description of kissing based on social behaviors involving intentional oral interaction with a member of the identical group, with some motion of the oral area but no transfer of food.

Study Methods

The lead researcher explained they focused on accounts of intimate behavior in non-human species from the African continent and Asian regions, including primates, chimpanzees and orangutans, and employed digital recordings to confirm the observations.

Scientists then integrated this data with details on the genetic connections between extant and extinct types of such animals.

Historical Origins

The team say the findings suggest kissing developed approximately 21.5m and 16.9m years ago in the predecessors of the large apes.

The position of Neanderthals on this evolutionary lineage suggests it is likely they, too, indulged in a intimate act, the researchers conclude. But the behavior might not have been confined to their specific group.

"Reality that humans engage intimately, the reality that we currently have demonstrated that ancient relatives probably kissed, indicates that the both groups are also likely to have kissed," the researcher added.

Biological Significance

Although the evolutionary explanation is debated, the expert said intimate contact could be used in sexual contexts to possibly enhance reproductive success or assist in selecting between mates, while it might help reinforce bonding when practiced in a non-sexual manner.

A separate researcher in the behavior of primates said that as kissing behavior was observed in a wide range of primates it made sense its origins extend far into our evolutionary past, and an examination of different forms of kissing among a wider variety of animals might extend its origins back even earlier still.

"Behaviors that we consider as signatures of human life, like intimate contact, are not unique to us if we examine carefully at other animals," he said.

Social Elements

Another professor said that kissing had a cultural element as it was not universal to all human groups.

"However, as people we succeed or struggle on the strength of our relationships, and methods of promoting trust and closeness will have been important for millions of years," the professor stated. "It might be an concept that appears a bit contradictory to our incorrect assumptions of a supposedly aggressive and aggressive past, but really it ought to be no surprise that Neanderthals – and even Neanderthals and our human ancestors together – kissed."