Ancient Hominins and Modern Humans Were Likely Engaging in Intimate Contact, Researchers Propose

Among seabirds to Arctic mammals, primates to great apes, various animals appear to kiss. Now, scientists propose that Neanderthals also engaged in this behavior – and might even have exchanged kisses with early Homo sapiens.

Common Oral Evidence

It is not the first time scientists have suggested Neanderthals and Homo sapiens were closely connected. In previous studies, scientists have found humans and their thick-browed cousins possessed the identical oral bacteria for millions of years after the two species split, suggesting they exchanged oral fluids.

"Probably they were kissing," the researcher noted, adding that the concept chimed with research that has found people of non-African ancestry contain Neanderthal DNA in their genetic makeup, revealing interbreeding was at play.

Intimate Spin

"It certainly puts a different perspective on ancient interactions," Brindle said.

Publishing in the journal Evolution and Human Behavior, Brindle and her team detail how, to investigate the evolutionary origins of kissing, they first had to come up with a description that was not restricted by how humans kiss.

Defining Kissing

"Previously there were some previous attempts to define a intimate act, but it's largely human-centric, which means that essentially other animals do not engage in this. Currently we know that they probably do, it may appear different from what human kissing looks like," explained the evolutionary biologist.

Nonetheless, she noted some behaviors that looked like intimate contact were something rather different – such as the chewing and transfer of food, or "kiss-fighting", observed in aquatic species known as French grunts.

As a result the team came up with a definition of intimate contact based on friendly interactions involving directed oral interaction with a member of the identical group, with some motion of the oral area but absence of nutrition.

Research Approach

The lead researcher said they focused on reports of kissing in primates from Africa and Asia, including primates, apes and orangutans, and employed online videos to verify the observations.

The researchers then integrated this data with information on the evolutionary relationships between living and extinct species of such primates.

Evolutionary Origins

Researchers say the results indicate intimate contact developed approximately 21.5m and 16.9m years ago in the ancestors of the great primates.

The position of Neanderthals on this evolutionary lineage suggests it is likely they, too, indulged in a kiss, the researchers conclude. But the behavior may not have been confined to their specific group.

"Reality that modern people engage intimately, the fact that we now have shown that ancient relatives probably engaged, indicates that the two [species] are probably did kissed," the researcher added.

Biological Significance

Although the evolutionary explanation is discussed, the expert said intimate contact could be employed in sexual contexts to possibly increase mating outcomes or assist in selecting between mates, while it could assist reinforce bonding when used in a platonic way.

Another expert in the activities of great apes said that as kissing behavior was observed in a broad spectrum of primates it made sense its origins lie deep in our ancient history, and an examination of different forms of kissing among a wider variety of species might push its beginnings back further still.

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

Social Aspects

An archaeology expert said that intimate contact had a social component 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 confidence and closeness will have been important for eons," she said. "This could represent an concept that appears a bit contradictory to our misplaced ideas of a supposedly aggressive and aggressive past, but actually it should be no surprise that ancient hominins – and including them and our own species together – engaged intimately."