🔗 Share this article

Among Galápagos albatrosses to Arctic mammals, primates to orangutans, various animals engage in mouth-to-mouth contact. Currently, researchers suggest that Neanderthals also engaged in this behavior – and possibly exchanged kisses with modern humans.

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 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," she said, adding that the concept aligned with research that has found people of certain genetic backgrounds have bits of ancient genetic material in their genetic makeup, revealing genetic mixing was occurring.

Intimate Interpretation

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

Publishing in the publication a scientific periodical, the researcher and colleagues detail how, to investigate the historical roots of kissing, they first had to come up with a description that was not restricted by how people smooch.

Describing Kissing

"There have been some efforts to describe a kiss, but it's largely human-centric, which implies that essentially other animals do not engage in this. Now we understand that they likely engage, it might just not look from what our intimate contact resembles," said Brindle.

However, she said some behaviors that looked like kissing were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", seen in fish known as certain marine animals.

As a result the research group developed a definition of kissing centered around social behaviors involving directed oral interaction with a individual of the same species, with some motion of the oral area but no transfer of food.

Research Approach

The lead researcher said they focused on reports of intimate behavior in primates from Africa and Asia, including bonobos, apes and great apes, and used online videos to confirm the observations.

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

Evolutionary Origins

The team say the findings suggest kissing developed approximately 21.5 million and 16.9 million years ago in the ancestors of the large apes.

Placement of Neanderthals on this family tree means it is likely 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 kiss, the reality that we currently have demonstrated that Neanderthals very likely engaged, indicates that the two [species] are probably did engage," the researcher noted.

Evolutionary Importance

Although the scientific reasoning is debated, Brindle explained intimate contact could be employed in sexual contexts to possibly enhance reproductive success or help choose between mates, while it might help reinforce bonding when practiced in a platonic way.

Another expert in the behavior of great apes said that as intimate contact was observed in a broad spectrum of primates it was logical its origins extend far into our ancient history, and an examination of different forms of kissing among a wider variety of animals might push its origins back even earlier still.

"Behaviors that we think of as characteristics of human life, like kissing, are not unique to us if we examine carefully at other animals," the expert noted.

Cultural Elements

An archaeology expert said that intimate contact had a cultural element as it was not common to all societies.

"Nonetheless, as people we succeed or struggle on the strength of our emotional bonds, and methods of promoting confidence and closeness will have been important for eons," she said. "It might be an concept that appears a bit incongruous to our incorrect assumptions of a rather ruthless and aggressive past, but actually it ought to be no surprise that ancient hominins – and even them and our human ancestors collectively – kissed."