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

From Galápagos albatrosses to Arctic mammals, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Now, scientists suggest that Neanderthals also engaged in this behavior – and might even have locked lips with modern humans.

Common Oral Clues

It is not the first time experts have suggested ancient relatives and early modern humans were intimately acquainted. Among earlier research, scientists have discovered humans and their Neanderthal relatives shared the identical oral bacteria for hundreds of thousands of years after the two species split, implying they swapped saliva.

"Probably they were kissing," she said, adding that the concept aligned with studies that has revealed humans of certain genetic backgrounds have bits of Neanderthal DNA in their genome, revealing genetic mixing was occurring.

Romantic Spin

"It certainly puts a different spin on ancient interactions," the lead researcher commented.

Writing in the journal a scientific periodical, Brindle and her team detail how, to explore the historical roots of intimate contact, they first had to develop a definition that was not restricted by how humans smooch.

Defining Kissing

"There have been some previous attempts to describe a kiss, but it's largely focused on humans, which implies that basically other animals don't kiss. Currently we know that they likely engage, it might just not look from what human kissing resembles," explained the evolutionary biologist.

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

As a result the research group came up with a description of kissing centered around social behaviors involving intentional oral interaction with a individual of the same species, with some motion of the oral area but no transfer of food.

Study Methods

The lead researcher said they focused on reports of intimate behavior in primates from the African continent and Asia, including primates, chimpanzees and great apes, and used digital recordings to confirm the observations.

The researchers then integrated this data with information on the evolutionary relationships between extant and ancient types of such primates.

Evolutionary Timeline

Researchers propose the findings suggest intimate contact developed somewhere between 21.5m and 16.9m years ago in the predecessors of the large apes.

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

"Reality that modern people engage intimately, the fact that we currently have shown that ancient relatives very likely engaged, suggests that the two [species] are also likely to have engage," Brindle added.

Evolutionary Significance

Although the evolutionary explanation is discussed, Brindle explained intimate contact could be used in sexual contexts to potentially enhance mating outcomes or help choose between mates, while it might help strengthen connections when used in a non-sexual manner.

Another expert in the behavior of primates commented that as kissing behavior was observed in a broad spectrum of primates it was logical its roots lie deep in our ancient history, and an examination of various types of kissing among a broader range of species might push its origins back even earlier still.

"Behaviors that we consider as characteristics of our species, like kissing, are not unique to us if we look closely at other animals," the expert noted.

Cultural Aspects

Another professor said that kissing had a social component as it was not common to all human groups.

"However, as people we succeed or struggle on the quality of our emotional bonds, and methods of encouraging confidence and closeness will have been significant for eons," the professor stated. "It might be an concept that seems a bit incongruous to our misplaced ideas of a rather ruthless and ancient history, but actually it should be no surprise that Neanderthals – and including Neanderthals and our human ancestors together – engaged intimately."