Ancient Hominins and Early Humans May Have Engaging in Intimate Contact, Scientists Suggest

Among Galápagos albatrosses to Arctic mammals, chimpanzees to orangutans, various animals appear to kiss. Now, researchers propose that ancient hominins also engaged in this behavior – and might even have exchanged kisses with modern humans.

Shared Oral Clues

This isn't the initial instance experts have proposed Neanderthals and early modern humans were closely connected. Among earlier research, scientists have discovered modern people and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the evolutionary divergence, implying they swapped saliva.

"Likely they were kissing," she said, explaining that the concept aligned with studies that has found humans of certain genetic backgrounds have bits of Neanderthal DNA in their genome, revealing genetic mixing was at play.

Romantic Interpretation

"This offers a different perspective on human-Neanderthal relations," Brindle said.

Writing in the publication a scientific periodical, Brindle and colleagues detail how, to investigate the evolutionary origins of kissing, they first had to come up with a definition that was not limited to how humans smooch.

Describing Kissing

"There have been some efforts to define a kiss, but it's very much been human-centric, which means that basically other animals do not engage in this. Now we understand that they likely engage, it might just not look from what human kissing looks like," said Brindle.

Nonetheless, she noted some behaviors that looked like intimate contact were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", seen in aquatic species called certain marine animals.

Consequently the research group came up with a definition of intimate contact based on friendly interactions involving intentional oral interaction with a individual of the same species, with some motion of the mouth but no transfer of food.

Study Methods

The lead researcher said they focused on accounts of kissing in non-human species from the African continent and Asian regions, including primates, apes and great apes, and employed digital recordings to verify the observations.

The researchers then combined this information with information on the evolutionary relationships between extant and extinct types of such animals.

Historical Origins

The team propose the results indicate kissing evolved approximately 21.5m and 16.9 million years ago in the predecessors of the large apes.

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

"Reality that modern people engage intimately, the fact that we now have demonstrated that Neanderthals probably engaged, indicates that the both groups are also likely to have kissed," the researcher noted.

Biological Importance

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

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

"Things that we consider as signatures of human life, like kissing, are not exclusive to us if we look closely at other animals," he said.

Cultural Elements

Another professor said that intimate contact had a cultural element as it was not common to all societies.

"Nonetheless, as people we succeed or struggle on the quality 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 aggressive past, but really it should be expected that Neanderthals – and including Neanderthals and our own species collectively – kissed."