Neanderthals and Modern Humans May Have Engaging in Intimate Contact, Scientists Suggest

Among Galápagos albatrosses to polar bears, primates to great apes, various animals appear to kiss. Currently, scientists propose that ancient hominins also engaged in this behavior – and possibly locked lips with early Homo sapiens.

Common Oral Clues

This isn't the initial instance experts have suggested Neanderthals and early modern humans were closely connected. Among previous studies, scientists have discovered humans and their thick-browed cousins shared the identical oral bacteria for hundreds of thousands of years after the two species split, implying they swapped saliva.

"Likely they were kissing," she said, adding that the idea chimed with studies that has revealed humans of non-African ancestry contain Neanderthal DNA in their genome, revealing interbreeding was at play.

Intimate Spin

"It certainly puts a more romantic spin on human-Neanderthal relations," Brindle commented.

Publishing in the journal Evolution and Human Behavior, the researcher and her team report how, to investigate the evolutionary origins of kissing, they first had to develop a definition that was not restricted by how humans smooch.

Describing Intimate Contact

"Previously there were some efforts to describe a kiss, but it's largely focused on humans, which implies that essentially non-human species do not engage in this. Now we know that they likely engage, it may appear different from what human kissing looks like," said the evolutionary biologist.

Nonetheless, she noted some actions that looked like intimate contact were distinct activities – such as the chewing and transfer of food, or "mouth contact", observed in aquatic species known as French grunts.

Consequently the team developed a definition of intimate contact based on social behaviors involving directed mouth-to-mouth contact with a individual of the same species, with some motion of the oral area but no transfer of food.

Research Approach

The lead researcher said they concentrated on reports of kissing in primates from the African continent and Asia, including primates, apes and great apes, and used digital recordings to verify the reports.

Scientists then combined this information with details on the genetic connections between living and extinct species of such primates.

Historical Timeline

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

The position of ancient hominins on this family tree suggests it is probable they, too, engaged in a intimate act, the scientists conclude. But the behavior might not have been limited to their own species.

"The fact that modern people kiss, the reality that we now have shown that Neanderthals very likely engaged, indicates that the two [species] are probably did kissed," Brindle added.

Biological Significance

Although the scientific reasoning is discussed, the expert said intimate contact could be used in reproductive situations to potentially enhance mating outcomes or help choose between mates, while it could assist reinforce bonding when practiced in a non-sexual manner.

Another expert in the activities of great apes said that as intimate contact was observed in a wide range of primates it made sense its roots lie deep in our ancient history, and an analysis of different forms of kissing among a wider variety of animals might push its beginnings back even earlier still.

"Behaviors that we think of as characteristics of our species, like intimate contact, are not exclusive to us if we examine carefully at different species," he said.

Social Elements

An archaeology expert said that intimate contact had a cultural element as it was not universal to all societies.

"Nonetheless, as humans we thrive or fail on the quality of our emotional bonds, and ways of encouraging trust and intimacy will have been significant for millions of years," she said. "This could represent an image that seems a bit incongruous to our misplaced ideas of a rather ruthless and ancient history, but actually it ought to be no surprise that Neanderthals – and even them and our own species together – engaged intimately."