🔗 Share this article

Among Galápagos albatrosses to polar bears, chimpanzees to great apes, certain species engage in mouth-to-mouth contact. Now, scientists propose that Neanderthals did it too – and possibly exchanged kisses with early Homo sapiens.

Common Oral Clues

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

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

Intimate Interpretation

"It certainly puts a more romantic perspective on human-Neanderthal relations," the lead researcher commented.

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

Describing Kissing

"There have been some efforts to define a kiss, but it's very much been focused on humans, which implies that basically non-human species don't kiss. Currently we understand that they likely engage, it may appear different from what our intimate contact looks like," said the evolutionary biologist.

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

Consequently the research group came up with a description of kissing centered around social behaviors involving directed mouth-to-mouth contact with a member of the identical group, with some movement of the mouth but absence of nutrition.

Study Approach

Brindle said they concentrated on reports of kissing in non-human species from Africa and Asian regions, including bonobos, chimpanzees and orangutans, and employed online videos to verify the observations.

The researchers then combined this data with information on the genetic connections between extant and ancient types of such animals.

Historical Origins

Researchers say the findings indicate kissing evolved approximately 21.5m and 16.9m years ago in the predecessors of the great primates.

The position of Neanderthals on this evolutionary lineage means it is likely they, too, engaged in a kiss, the researchers say. But the behavior may not have been confined to their specific group.

"The fact that humans engage intimately, the fact that we currently have shown that Neanderthals very likely engaged, suggests that the two [species] are probably did kissed," Brindle added.

Evolutionary Significance

Although the evolutionary explanation is debated, Brindle explained kissing could be employed in reproductive situations to possibly enhance mating outcomes or assist in selecting between partners, while it might help strengthen connections when used in a platonic way.

A separate researcher in the behavior of great apes said that as kissing behavior was seen in a broad spectrum of primates it was logical its origins lie deep in our ancient history, and an examination of different forms of kissing among a wider variety of animals might extend its beginnings back even earlier still.

"Behaviors that we consider as characteristics of our species, like kissing, are not exclusive to us if we look closely at other animals," he said.

Cultural Aspects

Another professor said that kissing had a social component as it was not common to all human groups.

"Nonetheless, as humans we succeed or struggle on the strength of our emotional bonds, and methods of promoting confidence and closeness will have been significant for eons," she said. "This could represent an concept that seems a bit contradictory to our misplaced ideas of a rather ruthless and ancient history, but actually it should be no surprise that Neanderthals – and including them and our own species collectively – kissed."