Ancient Hominins and Early Humans Were Likely Kissing, Researchers Propose

From seabirds to polar bears, primates to orangutans, various animals engage in mouth-to-mouth contact. Now, scientists propose that Neanderthals also engaged in this behavior – and might even have exchanged kisses with modern humans.

Common Oral Evidence

This isn't the initial instance scientists have suggested Neanderthals and Homo sapiens were closely connected. Among previous studies, scientists have discovered humans and their thick-browed cousins shared the identical oral bacteria for millions of years after the two species split, implying they exchanged oral fluids.

"Likely they were engaging in intimate contact," the researcher noted, adding that the idea chimed with research that has found people of non-African ancestry have bits of Neanderthal DNA in their genetic makeup, demonstrating genetic mixing was at play.

Romantic Spin

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

Publishing in the publication a scientific periodical, Brindle and colleagues report how, to explore the historical roots of kissing, they first had to come up with a description that was not limited to how people smooch.

Defining Kissing

"Previously there were some previous attempts to describe a intimate act, but it's largely focused on humans, which means that basically other animals don't kiss. Now we understand that they likely engage, it might just not look from what human kissing resembles," explained Brindle.

Nonetheless, she noted some behaviors that looked like intimate contact were distinct activities – such as the chewing and food sharing, or "kiss-fighting", seen in fish called certain marine animals.

Consequently the research group developed a definition of kissing centered around social behaviors involving intentional mouth-to-mouth contact with a member of the identical group, with some motion of the mouth but absence of nutrition.

Study Approach

Brindle explained they concentrated on reports of kissing in non-human species from Africa and Asian regions, including primates, chimpanzees and great apes, and used digital recordings to confirm the reports.

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

Historical Origins

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

Placement of Neanderthals on this family tree suggests it is likely they, too, engaged in a intimate act, the scientists say. But the activity may not have been limited to their specific group.

"The fact that modern people engage intimately, the reality that we now have shown that ancient relatives probably kissed, suggests that the both groups are also likely to have kissed," Brindle noted.

Evolutionary Importance

While the evolutionary explanation is debated, Brindle explained intimate contact could be used in sexual contexts to possibly increase reproductive success or help choose between mates, while it could assist reinforce bonding when practiced in a platonic way.

A separate researcher in the behavior of great apes said that as kissing behavior was seen in a wide range of primates it was logical its origins extend far into our ancient history, and an examination of different forms of intimate behavior among a broader range of animals might push its beginnings back further still.

"Behaviors that we think of as characteristics of our species, like kissing, are not unique to us if we examine carefully at other animals," he said.

Cultural Aspects

An archaeology expert explained that kissing 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 ways of encouraging trust and closeness will have been significant for millions of years," the professor stated. "It might be an image that appears a bit incongruous to our incorrect assumptions of a rather ruthless and aggressive past, but actually it ought to be expected that ancient hominins – and including them and our human ancestors together – engaged intimately."