Ancient Hominins and Early Humans Were Likely Engaging in Intimate Contact, Scientists Propose

From seabirds to polar bears, chimpanzees to great apes, certain species appear to kiss. Now, researchers suggest that ancient hominins also engaged in this behavior – and possibly exchanged kisses with early Homo sapiens.

Shared Microbial Clues

It is not the first time experts have suggested ancient relatives and early modern humans were closely connected. Among earlier research, scientists have discovered modern people and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the two species split, suggesting they exchanged oral fluids.

"Likely they were engaging in intimate contact," the researcher noted, adding that the concept chimed with research that has revealed humans of non-African ancestry have bits of ancient genetic material in their genetic makeup, revealing genetic mixing was at play.

Romantic Interpretation

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

Publishing in the publication a scientific periodical, Brindle and colleagues detail how, to explore the evolutionary origins of intimate contact, they first had to develop a definition that was not restricted by how people smooch.

Describing Intimate Contact

"There have been some previous attempts to define a intimate act, but it's very much been human-centric, which means that essentially other animals do not engage in this. Currently we understand that they likely engage, it may appear different from what human kissing resembles," explained the evolutionary biologist.

Nonetheless, she noted some actions that looked like kissing were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", observed in aquatic species known as French grunts.

As a result the team developed a definition of kissing based on social behaviors involving intentional mouth-to-mouth contact with a member of the same species, with some movement of the oral area but absence of nutrition.

Research Methods

The lead researcher explained they focused on reports of kissing in non-human species from the African continent and Asia, including bonobos, apes and orangutans, and used online videos to confirm the observations.

Scientists then combined this information with information on the genetic connections between living and extinct species of such primates.

Evolutionary Origins

Researchers say the results suggest kissing evolved approximately 21.5m and 16.9m years ago in the ancestors of the great primates.

The position of ancient hominins on this family tree suggests it is probable they, too, indulged in a kiss, the researchers say. But the behavior may not have been limited to their specific group.

"Reality that modern people kiss, the fact that we currently have demonstrated that ancient relatives probably kissed, suggests that the two [species] are also likely to have kissed," Brindle noted.

Biological Importance

While the scientific reasoning is discussed, the expert explained kissing could be employed in sexual contexts to possibly enhance reproductive success or help choose between partners, while it might help strengthen connections when practiced in a non-sexual manner.

A separate researcher in the activities of great apes said that as kissing behavior was observed in a wide range of apes it was logical its roots lie deep in our evolutionary past, and an examination of different forms of intimate behavior among a wider variety of species might extend its beginnings back further still.

"Things that we consider as characteristics of human life, like kissing, are not unique to us if we examine carefully at other animals," he said.

Cultural Elements

Another professor explained that kissing had a cultural element as it was not universal to all human groups.

"However, as people we succeed or struggle on the quality of our emotional bonds, and ways of promoting confidence and closeness will have been important for millions of years," she said. "This could represent an concept that seems a bit incongruous to our incorrect assumptions of a supposedly aggressive and aggressive past, but really it ought to be no surprise that ancient hominins – and even Neanderthals and our human ancestors together – engaged intimately."