🔗 Share this article

From seabirds to polar bears, primates to orangutans, various animals engage in mouth-to-mouth contact. Now, scientists propose that ancient hominins did it too – and might even have locked lips with early Homo sapiens.

Common Microbial Evidence

It is not the first time experts have suggested Neanderthals and Homo sapiens were closely connected. Among earlier research, scientists have found humans and their Neanderthal relatives shared the same mouth microbe for millions of years after the two species split, implying they swapped saliva.

"Likely they were kissing," she said, adding that the concept aligned with studies that has revealed people of certain genetic backgrounds have bits of ancient genetic material in their genetic makeup, demonstrating genetic mixing was occurring.

Romantic Spin

"It certainly puts a different perspective on ancient interactions," the lead researcher said.

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

Defining Kissing

"Previously there were some previous attempts to define a intimate act, but it's largely human-centric, which implies that basically other animals don't kiss. Now we know that they probably do, it might just not look from what our intimate contact resembles," explained Brindle.

Nonetheless, she noted some behaviors that looked like intimate contact were something rather different – such as the chewing and transfer of food, or "mouth contact", observed in aquatic species known as French grunts.

Consequently the team developed a description of intimate contact based on social behaviors involving intentional oral interaction with a individual of the identical group, with some movement of the mouth but no transfer of nutrition.

Research Methods

The lead researcher said they concentrated on accounts of kissing in non-human species from Africa and Asian regions, including bonobos, chimpanzees and orangutans, and employed online videos to verify the observations.

Scientists then integrated this data with details on the genetic connections between extant and extinct species of such primates.

Historical Origins

Researchers say the findings suggest kissing developed somewhere between 21.5m and 16.9m years ago in the predecessors of the great primates.

The position of Neanderthals on this family tree means it is probable they, too, indulged in a intimate act, the scientists say. But the activity may not have been limited to their own species.

"Reality that modern people engage intimately, the reality that we now have demonstrated that Neanderthals very likely engaged, indicates that the two [species] are probably did engage," the researcher noted.

Evolutionary Importance

Although the evolutionary explanation is debated, the expert said kissing could be used in sexual contexts to possibly enhance reproductive success or help choose between mates, while it could assist reinforce bonding when practiced in a non-sexual manner.

Another expert in the behavior of primates commented that as intimate contact was observed in a wide range of primates it made sense its origins lie deep in our ancient history, and an analysis of various types of intimate behavior among a broader range of animals might extend its origins back further still.

"Behaviors that we consider 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 cultural element as it was not common to all societies.

"Nonetheless, as humans we succeed or struggle on the strength of our relationships, and methods of encouraging trust and intimacy will have been important for eons," the professor stated. "This could represent an image that seems a bit contradictory to our incorrect assumptions of a supposedly aggressive and ancient history, but really it ought to be expected that ancient hominins – and even Neanderthals and our human ancestors collectively – engaged intimately."