Ancient Hominins and Early Humans Were Likely Kissing, Scientists Suggest

From Galápagos albatrosses to Arctic mammals, primates to great apes, various animals engage in mouth-to-mouth contact. Currently, scientists suggest that ancient hominins also engaged in this behavior – and possibly locked lips with early Homo sapiens.

Common Microbial Evidence

It is not the first time scientists have proposed Neanderthals and early modern humans were closely connected. In previous studies, researchers have discovered humans and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the evolutionary divergence, suggesting they swapped saliva.

"Likely they were kissing," the researcher noted, adding that the idea chimed with studies that has found humans of certain genetic backgrounds contain ancient genetic material in their genome, revealing interbreeding was at play.

Intimate Interpretation

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

Publishing in the journal a scientific periodical, Brindle and colleagues report how, to explore the evolutionary origins of intimate contact, they first had to develop a description that was not limited to how humans smooch.

Defining Kissing

"Previously there were some previous attempts to describe a kiss, but it's very much been focused on humans, which means that basically other animals do not engage in this. Currently we understand that they likely engage, it may appear different from what human kissing looks like," said the evolutionary biologist.

However, she noted some behaviors that resembled intimate contact were something rather different – such as the processing and food sharing, or "mouth contact", observed in aquatic species called certain marine animals.

Consequently the research group came up with a definition of kissing centered around social behaviors involving directed oral interaction with a member of the identical group, with some motion of the mouth but no transfer of nutrition.

Study Methods

Brindle explained they concentrated on reports of intimate behavior in primates from the African continent and Asia, including bonobos, apes and great apes, and used digital recordings to confirm the reports.

The researchers then integrated this information with details on the genetic connections between living and extinct species of such animals.

Historical Timeline

Researchers say the findings indicate intimate contact evolved somewhere between 21.5m and 16.9m years ago in the predecessors of the large apes.

The position of Neanderthals on this family tree suggests it is probable they, too, indulged in a intimate act, the scientists say. But the behavior might not have been confined to their own species.

"Reality that humans engage intimately, the reality that we currently have demonstrated that Neanderthals very likely engaged, suggests that the both groups are also likely to have kissed," Brindle noted.

Biological Importance

While the scientific reasoning is debated, Brindle explained kissing could be employed in sexual contexts to possibly enhance reproductive success or assist in selecting between mates, while it might help reinforce bonding when practiced in a platonic way.

A separate researcher in the activities of primates commented that as kissing behavior was seen in a wide range of primates it was logical its origins extend far into our evolutionary past, and an analysis of different forms of intimate behavior among a broader range of animals might extend its beginnings back even earlier still.

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

Cultural Elements

An archaeology expert explained that kissing had a social component as it was not common to all human groups.

"Nonetheless, as humans we thrive or fail on the strength of our emotional bonds, and methods of promoting trust and intimacy will have been significant for eons," she said. "It might be an concept that appears a bit incongruous to our incorrect assumptions of a rather ruthless and ancient history, but actually it should be expected that ancient hominins – and including Neanderthals and our own species collectively – kissed."