🔗 Share this article

Among Galápagos albatrosses to Arctic mammals, primates 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 exchanged kisses with modern humans.

Shared Microbial Clues

This isn't the initial instance experts have proposed ancient relatives and Homo sapiens were closely connected. Among previous studies, scientists have discovered humans and their Neanderthal relatives possessed the same mouth microbe for hundreds of thousands of years after the two species split, suggesting they swapped saliva.

"Likely they were engaging in intimate contact," she said, adding that the idea aligned with studies that has found humans of non-African ancestry contain ancient genetic material in their genome, revealing genetic mixing was at play.

Intimate Interpretation

"It certainly puts a more romantic spin on ancient interactions," Brindle commented.

Publishing in the journal Evolution and Human Behavior, the researcher and colleagues detail how, to investigate the historical roots of kissing, they first had to develop a definition that was not limited to how humans kiss.

Describing Intimate Contact

"Previously there were some efforts to define a kiss, but it's very much been focused on humans, which means that essentially non-human species do not engage in this. Currently we know that they likely engage, it might just not look from what human kissing looks like," said Brindle.

However, she said some actions that looked like kissing were distinct activities – such as the chewing and food sharing, or "mouth contact", seen in fish known as French grunts.

As a result the team developed a description of intimate contact centered around social behaviors involving directed oral interaction with a member of the same species, with some movement of the oral area but absence of food.

Study Methods

Brindle said they concentrated on accounts of intimate behavior in primates from the African continent and Asian regions, including bonobos, apes and great apes, and used online videos to verify the observations.

Scientists then combined this information with information on the evolutionary relationships between living and extinct species of such animals.

Evolutionary Timeline

Researchers propose the results indicate intimate contact evolved somewhere between 21.5 million and 16.9m years ago in the ancestors of the large apes.

Placement of ancient hominins on this family tree means it is probable they, too, engaged in a kiss, the scientists conclude. But the behavior might not have been confined to their own species.

"The fact that modern people engage intimately, the reality that we now have demonstrated that ancient relatives very likely kissed, suggests that the both groups are probably did engage," the researcher added.

Evolutionary Significance

While the scientific reasoning is discussed, the expert explained intimate contact could be employed in sexual contexts to possibly enhance mating outcomes or help choose between partners, while it could assist reinforce bonding when practiced in a platonic way.

A separate researcher in the activities of great apes commented that as intimate contact was seen in a wide range of primates it was logical its origins extend far into our ancient history, and an examination of various types of kissing among a broader range of animals might push its origins back further still.

"Behaviors that we consider as signatures of our species, like kissing, are not unique to us if we examine carefully at different species," 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 succeed or struggle on the strength of our relationships, and ways of promoting trust and intimacy will have been important for eons," the professor stated. "It might be an image that appears a bit contradictory to our incorrect assumptions of a rather ruthless and ancient history, but really it should be expected that Neanderthals – and including Neanderthals and our human ancestors collectively – engaged intimately."