🔗 Share this article

From Galápagos albatrosses to Arctic mammals, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Now, scientists propose that Neanderthals also engaged in this behavior – and possibly locked lips with early Homo sapiens.

Shared Microbial Evidence

It is not the first time experts have proposed Neanderthals and Homo sapiens were intimately acquainted. In earlier research, researchers have discovered modern people and their Neanderthal relatives shared the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, suggesting they swapped saliva.

"Probably they were engaging in intimate contact," the researcher noted, adding that the concept chimed with research that has revealed people of non-African ancestry have bits of ancient genetic material in their genetic makeup, revealing genetic mixing was at play.

Romantic Interpretation

"This offers a different spin on human-Neanderthal relations," the lead researcher said.

Writing in the journal Evolution and Human Behavior, the researcher and her team detail how, to investigate the evolutionary origins of intimate contact, they first had to develop a description that was not limited to how people smooch.

Defining Intimate Contact

"There have been some previous attempts to describe a intimate act, but it's very much been focused on humans, which means that basically non-human species do not engage in this. Currently we know that they likely engage, it may appear different from what our intimate contact looks like," explained Brindle.

Nonetheless, she noted some actions that resembled kissing were something rather different – such as the chewing and transfer of food, or "kiss-fighting", seen in aquatic species known as French grunts.

Consequently the team came up with a definition of kissing based on friendly interactions involving intentional oral interaction with a member of the identical group, with some motion of the mouth but absence of food.

Study Methods

Brindle explained they focused on reports of intimate behavior in primates from Africa and Asian regions, including bonobos, apes and great apes, and used online videos to verify the reports.

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

Evolutionary Origins

The team say the findings indicate kissing evolved somewhere between 21.5m and 16.9 million years ago in the predecessors of the great primates.

The position of Neanderthals on this family tree suggests it is likely they, too, indulged in a kiss, the scientists say. But the behavior may not have been confined to their own species.

"Reality that humans kiss, the fact that we now have demonstrated that Neanderthals probably engaged, suggests that the both groups are probably did engage," the researcher noted.

Biological Importance

While the scientific reasoning is debated, Brindle said kissing could be used in sexual contexts to possibly increase mating outcomes or assist in selecting between mates, while it might help reinforce bonding when practiced in a non-sexual manner.

Another expert in the behavior of great apes said that as intimate contact was seen in a wide range of primates it was logical its origins lie deep in our evolutionary past, and an analysis of various types of kissing among a broader range of animals might push its beginnings back further still.

"Behaviors that we think of as characteristics of our species, like intimate contact, are not unique to us if we look closely at different species," the expert noted.

Cultural Elements

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

"Nonetheless, as humans we succeed or struggle on the quality of our relationships, and methods of promoting confidence and intimacy will have been important for eons," she said. "It might be an concept that seems a bit incongruous to our incorrect assumptions of a rather ruthless and ancient history, but really it should be no surprise that ancient hominins – and even Neanderthals and our human ancestors collectively – engaged intimately."