Ancient Hominins and Modern Humans Were Likely Kissing, Scientists Suggest

From seabirds to Arctic mammals, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Now, scientists propose that ancient hominins also engaged in this behavior – and possibly locked lips with modern humans.

Shared Oral Clues

This isn't the initial instance scientists 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 hundreds of thousands of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Probably they were engaging in intimate contact," the researcher noted, adding that the idea chimed with research that has revealed humans of certain genetic backgrounds have bits of ancient genetic material in their genetic makeup, revealing genetic mixing was at play.

Romantic Spin

"This offers a different spin on ancient interactions," Brindle commented.

Publishing in the journal Evolution and Human Behavior, the researcher and colleagues report how, to investigate the evolutionary origins of intimate contact, they first had to develop a definition that was not restricted by how humans kiss.

Defining Intimate Contact

"There have been some efforts to describe a kiss, but it's very much been focused on humans, which means that basically other animals don't kiss. Now we know that they probably do, it may appear different from what human kissing looks like," said the evolutionary biologist.

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 fish known as French grunts.

As a result the research group developed a description of kissing centered around friendly interactions involving directed mouth-to-mouth contact with a member of the identical group, with some movement of the mouth but absence of food.

Study Approach

Brindle said they concentrated on accounts of kissing in non-human species from Africa and Asian regions, including bonobos, chimpanzees and orangutans, and used digital recordings to verify the observations.

Scientists then integrated this information with details on the evolutionary relationships between living and extinct types of such primates.

Historical Origins

The team say the findings indicate kissing developed approximately 21.5 million and 16.9m 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 scientists conclude. But the behavior might not have been confined to their specific group.

"Reality that modern people kiss, the reality that we now have shown that ancient relatives probably engaged, indicates that the both groups are also likely to have engage," the researcher added.

Biological Significance

While the scientific reasoning is discussed, Brindle said kissing could be used in reproductive situations to possibly enhance mating outcomes or assist in selecting between mates, while it could assist reinforce bonding when practiced in a non-sexual manner.

Another expert in the activities of great apes said that as intimate contact was observed in a wide range of apes it made sense its origins lie deep in our ancient history, and an analysis of different forms of kissing among a broader range of species might extend its origins back even earlier still.

"Things that we think of as characteristics of our species, like intimate contact, are not unique to us if we look closely at different species," he said.

Social Elements

Another professor said that kissing had a social component as it was not universal to all societies.

"Nonetheless, as people we succeed or struggle on the strength of our relationships, and ways of encouraging confidence and intimacy will have been important for eons," the professor stated. "This could represent an image that appears a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but actually it ought to be no surprise that ancient hominins – and including Neanderthals and our human ancestors collectively – kissed."