🔗 Share this article

Among Galápagos albatrosses to polar bears, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Currently, scientists propose that Neanderthals did it too – and might even have exchanged kisses with modern humans.

Shared Oral Clues

This isn't the initial instance experts have suggested ancient relatives and early modern humans were closely connected. Among previous studies, scientists have discovered humans and their thick-browed cousins shared the same mouth microbe for millions of years after the two species split, suggesting they exchanged oral fluids.

"Probably they were engaging in intimate contact," the researcher noted, explaining that the concept chimed with studies that has found humans of certain genetic backgrounds contain Neanderthal DNA in their genome, demonstrating genetic mixing was at play.

Romantic Spin

"This offers a more romantic spin on human-Neanderthal relations," Brindle commented.

Writing in the journal a scientific periodical, Brindle and colleagues detail how, to investigate the evolutionary origins of intimate contact, they first had to come up with a definition that was not limited to how humans smooch.

Describing Kissing

"There have been some efforts to describe a kiss, but it's largely focused on humans, which implies that basically 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," explained the evolutionary biologist.

Nonetheless, she noted some actions that looked like kissing were something rather different – such as the processing and transfer of food, or "mouth contact", observed in aquatic species called certain marine animals.

As a result the research group came up with a description of intimate contact based on social behaviors involving directed mouth-to-mouth contact with a individual of the same species, with some movement of the mouth but absence of food.

Research Methods

The lead researcher explained they focused on reports of intimate behavior in primates from Africa and Asia, including bonobos, apes and orangutans, and used digital recordings to verify the reports.

The researchers then combined this information with details on the genetic connections between living and extinct types of such animals.

Evolutionary Origins

The team say the results indicate kissing developed approximately 21.5m and 16.9 million years ago in the ancestors of the large apes.

The position of Neanderthals on this evolutionary lineage suggests it is probable they, too, engaged in a kiss, the scientists say. But the activity may not have been limited to their specific group.

"Reality that modern people engage intimately, the reality that we now have demonstrated that Neanderthals probably kissed, suggests that the both groups are also likely to have engage," Brindle added.

Biological Significance

Although the evolutionary explanation is debated, Brindle explained kissing could be used in reproductive situations to possibly enhance reproductive success or help choose between partners, while it might help reinforce bonding when practiced in a non-sexual manner.

A separate researcher in the activities of great apes said that as kissing behavior was seen in a broad spectrum of apes it was logical its roots lie deep in our ancient history, and an examination of different forms of kissing among a broader range of species might push its beginnings back further still.

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

Cultural Aspects

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

"Nonetheless, as people we succeed or struggle on the quality of our relationships, and ways of promoting trust 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 incorrect assumptions of a supposedly aggressive and aggressive past, but actually it should be expected that ancient hominins – and even Neanderthals and our own species together – engaged intimately."