🔗 Share this article

From Galápagos albatrosses to Arctic mammals, primates to great apes, various animals appear to kiss. Now, scientists suggest that ancient hominins did it too – and might even have locked lips with early Homo sapiens.

Shared Oral Clues

This isn't the initial instance scientists have suggested Neanderthals and early modern humans were intimately acquainted. Among earlier research, scientists have discovered humans and their Neanderthal relatives shared the same mouth microbe for millions of years after the two species split, implying they swapped saliva.

"Likely they were engaging in intimate contact," the researcher noted, explaining that the concept chimed with studies that has revealed humans of certain genetic backgrounds contain Neanderthal DNA in their genome, demonstrating interbreeding was occurring.

Intimate Spin

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

Writing in the publication Evolution and Human Behavior, the researcher and her team detail how, to investigate the historical roots of intimate contact, they first had to come up with a description that was not limited to how humans kiss.

Defining Intimate Contact

"There have been some previous attempts to define a intimate act, but it's very much been human-centric, which implies that essentially non-human species don't kiss. Currently we understand that they probably do, it might just not look from what our intimate contact looks like," explained the evolutionary biologist.

Nonetheless, she said some behaviors that resembled intimate contact were something rather different – such as the processing and transfer of food, or "kiss-fighting", observed in fish known as French grunts.

Consequently the team developed a definition of intimate contact based on friendly interactions involving directed oral interaction with a member of the same species, with some motion of the oral area but absence of nutrition.

Research Methods

Brindle said they focused on reports of kissing in non-human species from Africa and Asia, including bonobos, apes and orangutans, and used digital recordings to confirm the observations.

The researchers then integrated this data with information on the genetic connections between living and extinct types of such primates.

Evolutionary Origins

Researchers propose the findings indicate kissing evolved somewhere between 21.5m and 16.9m years ago in the ancestors of the large apes.

The position of ancient hominins on this family tree means it is probable they, too, indulged in a intimate act, the researchers conclude. But the behavior may 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 kissed, suggests that the both groups are probably did kissed," the researcher added.

Biological Significance

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

A separate researcher in the behavior of great apes commented that as kissing behavior was observed in a broad spectrum of primates it was logical its roots lie deep in our ancient history, and an analysis of different forms of intimate behavior among a broader range of animals might push its beginnings back further still.

"Things that we consider as signatures of our species, like intimate contact, are not unique to us if we look closely at other animals," he said.

Social Elements

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

"Nonetheless, as humans we thrive or fail on the strength of our relationships, and ways of encouraging trust and closeness will have been significant for millions of years," the professor stated. "This could represent an concept that appears a bit incongruous to our misplaced ideas of a rather ruthless and aggressive past, but actually it ought to be no surprise that ancient hominins – and even Neanderthals and our own species together – kissed."