🔗 Share this article

Among seabirds to polar bears, chimpanzees to great apes, certain species engage in mouth-to-mouth contact. Now, scientists propose that ancient hominins did it too – and possibly locked lips with early Homo sapiens.

Shared Microbial Evidence

This isn't the initial instance scientists have suggested Neanderthals and early modern humans were intimately acquainted. Among previous studies, researchers have discovered humans and their thick-browed cousins possessed the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, implying they swapped saliva.

"Likely they were kissing," she said, explaining that the concept chimed with research that has revealed people of non-African ancestry have bits of ancient genetic material in their genome, revealing genetic mixing was occurring.

Intimate Interpretation

"This offers a different perspective on human-Neanderthal relations," Brindle commented.

Writing in the journal a scientific periodical, Brindle and her team detail how, to explore the evolutionary origins of intimate contact, they first had to develop a definition that was not restricted by how humans smooch.

Defining Kissing

"There have been some previous attempts to define a kiss, but it's largely focused on humans, 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 our intimate contact looks like," explained Brindle.

Nonetheless, she said some actions that looked like kissing were distinct activities – such as the chewing and transfer of food, or "mouth contact", seen in aquatic species known as French grunts.

Consequently the research group came up with a description of kissing based on social behaviors involving directed mouth-to-mouth contact with a member of the same species, with some movement of the oral area but absence of food.

Study Approach

Brindle explained they focused on reports of kissing in non-human species from the African continent and Asian regions, including bonobos, apes and orangutans, and employed online videos to confirm the observations.

Scientists then integrated this data with details on the evolutionary relationships between living and ancient species of such primates.

Evolutionary Origins

Researchers say the results indicate intimate contact 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 suggests it is likely they, too, engaged in a intimate act, the researchers conclude. But the activity might not have been confined to their specific group.

"The fact that modern people engage intimately, the fact that we currently have demonstrated that Neanderthals probably engaged, suggests that the both groups are probably did engage," Brindle added.

Biological Significance

While the evolutionary explanation is debated, the expert explained intimate contact could be used in reproductive situations to potentially increase reproductive success or help choose between mates, while it might help strengthen connections when practiced in a non-sexual manner.

Another expert in the behavior of primates said that as kissing behavior 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 kissing among a wider variety of animals might extend its origins back further still.

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

Social Elements

An archaeology expert said that kissing had a cultural element as it was not common to all human groups.

"Nonetheless, as people we succeed or struggle on the strength of our emotional bonds, and methods of encouraging trust and intimacy will have been significant for eons," the professor stated. "This could represent an concept that appears a bit contradictory to our incorrect assumptions of a rather ruthless and ancient history, but really it ought to be no surprise that Neanderthals – and even Neanderthals and our own species collectively – kissed."