Ancient Hominins and Modern Humans May Have Kissing, Researchers Propose

Among Galápagos albatrosses to polar bears, primates to orangutans, certain species engage in mouth-to-mouth contact. Now, researchers suggest that ancient hominins did it too – and possibly exchanged kisses with modern humans.

Common Oral Evidence

It is not the first time experts have proposed ancient relatives and early modern humans were intimately acquainted. Among previous studies, researchers have discovered humans and their Neanderthal relatives shared the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, implying they exchanged oral fluids.

"Likely they were engaging in intimate contact," she said, adding that the idea chimed with research that has found humans of certain genetic backgrounds have bits of ancient genetic material in their genome, demonstrating interbreeding was at play.

Romantic Spin

"It certainly puts a different spin on human-Neanderthal relations," Brindle said.

Publishing in the publication a scientific periodical, the researcher and her team detail how, to investigate the evolutionary origins of kissing, they first had to come up with a description that was not restricted by how humans smooch.

Describing Intimate Contact

"Previously there were some efforts to define a kiss, but it's very much been human-centric, which means that essentially other animals do not engage in this. Now we know that they probably do, it might just not look from what our intimate contact looks like," said the evolutionary biologist.

Nonetheless, she said some behaviors that resembled kissing were distinct activities – such as the chewing and food sharing, or "mouth contact", seen in fish known as French grunts.

As a result the research group came up with a definition of intimate contact centered around social behaviors involving intentional mouth-to-mouth contact with a member of the same species, with some motion of the mouth but absence of nutrition.

Research Approach

Brindle explained they focused on reports of intimate behavior in primates from Africa and Asian regions, including primates, apes and orangutans, and used digital recordings to confirm the reports.

The researchers then integrated this data with information on the evolutionary relationships between extant and extinct species of such animals.

Evolutionary Timeline

Researchers say the findings suggest kissing evolved approximately 21.5m and 16.9 million years ago in the predecessors of the large apes.

Placement of ancient hominins on this evolutionary lineage suggests it is likely they, too, indulged in a kiss, the researchers say. But the behavior may not have been limited to their specific group.

"The fact that humans kiss, the reality that we currently have shown that ancient relatives very likely engaged, suggests that the both groups are also likely to have engage," Brindle noted.

Biological Importance

Although the evolutionary explanation is debated, Brindle explained intimate contact could be employed in reproductive situations to potentially enhance mating outcomes or assist in selecting between partners, while it might help reinforce bonding when used in a non-sexual manner.

A separate researcher in the activities of primates commented that as kissing behavior was observed in a broad spectrum of apes it made sense its roots lie deep in our evolutionary past, and an analysis of various types of kissing among a wider variety of species might extend its beginnings back even earlier still.

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

Social Elements

An archaeology expert said that kissing had a cultural element as it was not universal to all societies.

"Nonetheless, as humans we thrive or fail on the strength of our emotional bonds, and methods of promoting trust and closeness will have been significant for eons," the professor stated. "This could represent an image that seems a bit contradictory to our incorrect assumptions of a rather ruthless and aggressive past, but actually it ought to be no surprise that Neanderthals – and even Neanderthals and our human ancestors together – engaged intimately."