Ancient Hominins and Modern Humans Were Likely Engaging in Intimate Contact, Researchers Propose

From Galápagos albatrosses to polar bears, chimpanzees to orangutans, certain species appear to kiss. Currently, researchers propose that ancient hominins did it too – and possibly exchanged kisses with modern humans.

Common Oral Evidence

This isn't the initial instance experts have proposed ancient relatives and Homo sapiens were intimately acquainted. In previous studies, scientists have discovered modern people and their Neanderthal relatives shared the identical oral bacteria for millions of years after the two species split, suggesting they exchanged oral fluids.

"Probably they were engaging in intimate contact," she said, adding that the concept aligned with studies that has revealed humans of non-African ancestry have bits of Neanderthal DNA in their genome, revealing interbreeding was at play.

Romantic Interpretation

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

Publishing in the publication Evolution and Human Behavior, the researcher and her team detail how, to explore the evolutionary origins of intimate contact, they first had to develop a description that was not limited to how people kiss.

Defining Kissing

"Previously there were some efforts to describe a kiss, but it's largely focused on humans, which means that basically non-human species don't kiss. Currently we understand that they likely engage, it may appear different from what human kissing looks like," said the evolutionary biologist.

Nonetheless, she noted some behaviors that resembled intimate contact were distinct activities – such as the chewing and transfer of food, or "mouth contact", seen in aquatic species called French grunts.

Consequently the research group developed a definition of kissing based on friendly interactions involving directed mouth-to-mouth contact with a member of the same species, with some movement of the mouth but no transfer of food.

Study Methods

The lead researcher said they focused on reports of kissing in primates from Africa and Asia, including primates, chimpanzees and great apes, and employed digital recordings to verify the observations.

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

Historical Origins

Researchers propose the findings suggest intimate contact developed somewhere between 21.5m and 16.9 million years ago in the predecessors of the large apes.

Placement of Neanderthals on this evolutionary lineage suggests it is likely they, too, engaged in a kiss, the scientists say. But the activity may not have been limited to their specific group.

"Reality that modern people kiss, the fact that we currently have demonstrated that Neanderthals very likely engaged, suggests that the two [species] are probably did kissed," the researcher added.

Biological Importance

Although the scientific reasoning is discussed, Brindle explained intimate contact could be used in reproductive situations to potentially enhance reproductive success or help choose between mates, while it could assist strengthen connections when practiced in a non-sexual manner.

A separate researcher in the activities of great apes said that as intimate contact was observed in a wide range of primates it was logical its roots extend far into our ancient history, and an analysis of various types of intimate behavior among a wider variety of animals might push its origins back further still.

"Behaviors that we consider as characteristics of our species, like kissing, are not exclusive to us if we examine carefully at different species," the expert noted.

Cultural Elements

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

"Nonetheless, as people we succeed or struggle on the strength of our emotional bonds, and methods of encouraging trust and closeness will have been important for millions of years," she said. "It might be an concept that seems a bit contradictory to our incorrect assumptions of a rather ruthless and ancient history, but actually it should be no surprise that ancient hominins – and even them and our human ancestors together – engaged intimately."