Ancient Hominins and Modern Humans May Have Engaging in Intimate Contact, Researchers Propose

Among Galápagos albatrosses to Arctic mammals, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Now, researchers suggest that Neanderthals did it too – and might even have exchanged kisses with modern humans.

Common Oral Evidence

This isn't the initial instance experts have suggested ancient relatives and early modern humans were intimately acquainted. In previous studies, scientists have discovered humans and their Neanderthal relatives shared the same mouth microbe for millions of years after the evolutionary divergence, suggesting they swapped saliva.

"Likely they were engaging in intimate contact," the researcher noted, adding that the idea chimed with research that has revealed people of non-African ancestry have bits of Neanderthal DNA in their genome, revealing genetic mixing was occurring.

Romantic Spin

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

Publishing in the publication Evolution and Human Behavior, the researcher and her team detail how, to explore the evolutionary origins of kissing, they first had to come up with a definition that was not limited to how people kiss.

Defining Kissing

"There have been some efforts to define a kiss, but it's largely focused on humans, which means that essentially other animals do not engage in this. Now we know that they probably do, it may appear different from what human kissing looks like," explained the evolutionary biologist.

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

As a result the research group 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 mouth but absence of food.

Research Methods

Brindle explained they concentrated on accounts of kissing in non-human species from Africa and Asian regions, including bonobos, apes and orangutans, and employed digital recordings to confirm the observations.

The researchers then integrated this information with details on the evolutionary relationships between living and ancient species of such animals.

Evolutionary Origins

Researchers propose the findings suggest kissing developed approximately 21.5m and 16.9 million years ago in the ancestors of the great primates.

Placement of ancient hominins on this evolutionary lineage suggests it is likely they, too, indulged in a kiss, the scientists conclude. But the behavior may not have been confined to their own species.

"The fact that modern people kiss, the fact that we currently have demonstrated that ancient relatives very likely engaged, indicates that the both groups are also likely to have engage," Brindle noted.

Biological Importance

Although the scientific reasoning is debated, the expert said kissing could be used in sexual contexts to potentially increase mating outcomes or assist in selecting between partners, while it could assist reinforce bonding when practiced in a non-sexual manner.

Another expert in the activities of primates commented that as kissing behavior was observed in a broad spectrum of apes it made sense its roots lie deep in our evolutionary past, and an examination of different forms of kissing among a wider variety of animals might extend its beginnings back further still.

"Behaviors that we think of as characteristics of our species, like kissing, are not unique to us if we examine carefully at different species," the expert noted.

Cultural Elements

Another professor said that intimate contact had a cultural element as it was not universal to all human groups.

"However, as people we thrive or fail on the quality of our emotional bonds, 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 incorrect assumptions of a supposedly aggressive and aggressive past, but really it ought to be expected that Neanderthals – and including them and our human ancestors together – engaged intimately."