🔗 Share this article

Among seabirds to polar bears, chimpanzees to great apes, various animals appear to kiss. Currently, scientists propose that Neanderthals did it too – and might even have exchanged kisses with early Homo sapiens.

Common Oral Clues

It is not the first time experts have suggested Neanderthals and Homo sapiens were intimately acquainted. Among previous studies, scientists have found modern people and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the two species split, implying they exchanged oral fluids.

"Probably they were kissing," she said, explaining that the idea chimed with studies that has found humans of certain genetic backgrounds contain Neanderthal DNA in their genome, demonstrating genetic mixing was at play.

Romantic Interpretation

"It certainly puts a more romantic spin on ancient interactions," the lead researcher said.

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

Defining Intimate Contact

"Previously there were some previous attempts to define a intimate act, but it's very much been human-centric, which implies that basically other animals do not engage in this. Currently we know that they likely engage, it might just not look from what human kissing looks like," said Brindle.

Nonetheless, she said some actions that resembled kissing were something rather different – such as the chewing and food sharing, or "mouth contact", observed in aquatic species known as French grunts.

As a result the research group came up with a definition of intimate contact based on social behaviors involving directed oral interaction with a member of the same species, with some motion of the oral area but no transfer of food.

Study Methods

Brindle explained they concentrated on reports of kissing in primates from Africa and Asian regions, including primates, apes and orangutans, and employed online videos to confirm the reports.

Scientists then integrated this data with details on the evolutionary relationships between extant and extinct types of such animals.

Evolutionary Timeline

The team say the results suggest kissing developed somewhere between 21.5m and 16.9 million years ago in the predecessors of the large apes.

Placement of Neanderthals on this family tree suggests it is probable they, too, engaged in a kiss, the researchers conclude. But the behavior may not have been limited to their own species.

"The fact that modern people kiss, the reality that we now have shown that Neanderthals probably engaged, indicates that the both groups are also likely to have kissed," the researcher noted.

Biological Importance

While the evolutionary explanation is discussed, Brindle said kissing could be employed in reproductive situations to possibly enhance mating outcomes or help choose between partners, while it might help strengthen connections when practiced in a non-sexual manner.

A separate researcher in the activities of great apes said that as intimate contact was seen in a broad spectrum of primates it made sense its roots extend far into our evolutionary past, and an analysis of various types of intimate behavior among a wider variety of species might extend its beginnings back even earlier still.

"Behaviors that we think of as signatures of human life, like intimate contact, are not exclusive to us if we examine carefully at other animals," the expert noted.

Cultural Elements

Another professor said that kissing had a social component as it was not universal to all societies.

"However, as people we thrive or fail on the strength of our relationships, and ways of promoting confidence and closeness will have been important for millions of years," the professor stated. "It might be an image that appears a bit incongruous to our misplaced ideas of a rather ruthless and aggressive past, but really it ought to be no surprise that ancient hominins – and including them and our human ancestors together – engaged intimately."