🔗 Share this article

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

Shared Oral Clues

It is not the first time experts have suggested ancient relatives and early modern humans were intimately acquainted. In previous studies, scientists have found modern people and their Neanderthal relatives possessed the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, suggesting 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 ancient genetic material in their genome, revealing interbreeding was occurring.

Romantic Interpretation

"This offers a different spin on ancient interactions," the lead researcher commented.

Writing in the journal a scientific periodical, the researcher and colleagues report how, to investigate the historical roots of kissing, they first had to develop a definition that was not limited to how people smooch.

Defining Intimate Contact

"There have been some efforts to describe a intimate act, but it's very much been focused on humans, which implies that basically other animals do not engage in this. Now we know that they likely engage, it may appear different from what human kissing resembles," explained the evolutionary biologist.

However, she said 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 certain marine animals.

As a result the research group developed a definition of kissing centered around social behaviors involving directed mouth-to-mouth contact with a member of the same species, with some movement of the oral area but absence of nutrition.

Study Approach

The lead researcher said they concentrated on accounts of intimate behavior in primates from Africa and Asian regions, including bonobos, chimpanzees and orangutans, and used online videos to confirm the reports.

The researchers then combined this data with details on the genetic connections between living and ancient species of such primates.

Historical Timeline

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

Placement of Neanderthals on this family tree means it is probable they, too, engaged in a kiss, the researchers say. But the activity might not have been limited to their own species.

"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 added.

Evolutionary Importance

Although the evolutionary explanation is debated, Brindle said kissing could be used in sexual contexts to potentially increase mating outcomes or assist in selecting between partners, while it could assist strengthen connections when used in a non-sexual manner.

A separate researcher in the activities of great apes said that as kissing behavior was observed in a wide range of apes it was logical its roots extend far into our ancient history, and an examination of different forms of kissing among a wider variety of animals might push its beginnings back even earlier still.

"Things that we think of as characteristics of human life, like intimate contact, are not unique to us if we examine carefully at different species," the expert noted.

Cultural Elements

Another professor explained that intimate contact had a social component as it was not common to all societies.

"Nonetheless, as people we succeed or struggle on the strength of our emotional bonds, and methods of encouraging confidence and closeness 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 aggressive past, but actually it should be expected that Neanderthals – and even them and our own species together – engaged intimately."