🔗 Share this article

Among Galápagos albatrosses to Arctic mammals, primates to orangutans, certain species appear to kiss. Now, scientists propose that ancient hominins also engaged in this behavior – and might even have exchanged kisses with modern humans.

Shared Oral Evidence

This isn't the initial instance experts have proposed Neanderthals and early modern humans were intimately acquainted. Among previous studies, scientists have discovered modern people and their Neanderthal relatives possessed the identical oral bacteria for hundreds of thousands of years after the two species split, implying they swapped saliva.

"Probably they were kissing," the researcher noted, explaining that the idea chimed with research that has found humans of certain genetic backgrounds have bits of Neanderthal DNA in their genome, revealing interbreeding was at play.

Romantic Spin

"This offers a more romantic spin on human-Neanderthal relations," the lead researcher commented.

Writing in the publication a scientific periodical, the researcher and her team detail how, to investigate the evolutionary origins of intimate contact, they first had to develop a description that was not restricted by how people smooch.

Describing Intimate Contact

"There have been 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. Now we know that they likely engage, it might just not look from what human kissing resembles," explained Brindle.

However, she noted some actions that resembled kissing were distinct activities – such as the chewing and food sharing, or "kiss-fighting", observed in aquatic species called certain marine animals.

As a result the team developed a definition of kissing based on friendly interactions involving intentional mouth-to-mouth contact with a member of the same species, with some motion of the oral area but absence of food.

Study Methods

Brindle explained they concentrated on accounts of intimate behavior in primates from Africa and Asia, including bonobos, apes and great apes, and employed online videos to confirm the observations.

The researchers then combined this information with details on the evolutionary relationships between living and ancient species of such animals.

Evolutionary Origins

Researchers propose the findings indicate intimate contact evolved approximately 21.5m and 16.9 million years ago in the ancestors of the large apes.

Placement of ancient hominins on this evolutionary lineage suggests it is probable they, too, engaged in a kiss, the scientists say. But the behavior might not have been confined to their specific group.

"The fact that humans engage intimately, the fact that we currently have shown that Neanderthals very likely engaged, indicates that the two [species] are also likely to have engage," the researcher noted.

Evolutionary Importance

While the evolutionary explanation is debated, the expert explained intimate contact could be used in sexual contexts to possibly enhance reproductive success or assist in selecting between partners, while it might help strengthen connections when practiced in a non-sexual manner.

Another expert in the activities of great apes commented that as intimate contact was seen in a broad spectrum of primates it was logical its origins extend far into our evolutionary past, and an analysis of different forms of intimate behavior among a wider variety of animals might extend its origins back even earlier still.

"Behaviors that we consider as signatures of human life, like kissing, are not exclusive to us if we look closely at different species," the expert noted.

Cultural Aspects

Another professor explained that intimate contact had a social component as it was not universal to all human groups.

"However, as humans we thrive or fail on the strength of our emotional bonds, and ways of encouraging confidence and closeness will have been significant for millions of years," she said. "It might be an concept that appears a bit contradictory to our misplaced ideas of a supposedly aggressive and aggressive past, but really it ought to be expected that ancient hominins – and including them and our own species collectively – engaged intimately."