Ancient Hominins and Modern Humans Were Likely Kissing, Researchers Suggest

Among seabirds to polar bears, primates to orangutans, various animals appear to kiss. Currently, researchers propose that Neanderthals did it too – and might even have locked lips with early Homo sapiens.

Common Oral Clues

This isn't the initial instance experts have suggested Neanderthals and early modern humans were intimately acquainted. Among previous studies, researchers have found humans and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Likely they were engaging in intimate contact," the researcher noted, explaining that the concept aligned with research that has found people of non-African ancestry contain ancient genetic material in their genetic makeup, demonstrating genetic mixing was occurring.

Intimate Spin

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

Writing in the publication Evolution and Human Behavior, the researcher and her team report how, to investigate the historical roots of intimate contact, they first had to come up with a definition that was not limited to how humans kiss.

Describing Kissing

"Previously there were some previous attempts to describe a kiss, but it's very much been human-centric, which means that basically non-human species do not engage in this. Now we know that they likely engage, it might just not look from what our intimate contact resembles," said the evolutionary biologist.

Nonetheless, she noted some behaviors that resembled kissing were something rather different – such as the chewing and transfer of food, or "mouth contact", observed in fish called French grunts.

As a result the team developed a description of kissing centered around friendly interactions involving directed oral interaction with a member of the identical group, with some movement of the mouth but no transfer of food.

Research Methods

Brindle said they focused on reports of kissing in non-human species from Africa and Asia, including bonobos, apes and great apes, and used digital recordings to confirm the observations.

The researchers then combined this data with details on the genetic connections between extant and ancient species of such animals.

Historical Timeline

The team say the results suggest intimate contact evolved somewhere between 21.5 million and 16.9 million years ago in the ancestors of the large apes.

Placement of Neanderthals on this family tree suggests it is probable they, too, indulged in a kiss, the researchers conclude. But the behavior 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 very likely engaged, indicates that the two [species] are also likely to have kissed," the researcher noted.

Evolutionary Significance

Although the evolutionary explanation is debated, the expert explained intimate contact could be employed in sexual contexts to potentially increase reproductive success or assist in selecting between mates, while it might help reinforce bonding when used in a platonic way.

A separate researcher in the activities of primates said that as intimate contact was observed in a wide range of primates it was logical its origins lie deep in our ancient history, and an examination of different forms of kissing among a broader range of animals might extend its origins back even earlier still.

"Behaviors that we think of as signatures of our species, like intimate contact, are not unique to us if we look closely at other animals," the expert noted.

Social Aspects

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

"Nonetheless, as humans we thrive or fail on the strength of our relationships, and ways of encouraging trust and intimacy will have been important for eons," she said. "It might be an image that appears a bit contradictory to our misplaced ideas of a rather ruthless and ancient history, but really it should be no surprise that ancient hominins – and even them and our human ancestors collectively – engaged intimately."