Ancient Hominins and Early Humans May Have Kissing, Scientists Suggest

Among seabirds to Arctic mammals, chimpanzees to great apes, certain species appear to kiss. Currently, scientists propose that ancient hominins did it too – and possibly locked lips with modern humans.

Shared Oral Clues

It is not the first time scientists have suggested Neanderthals and Homo sapiens were closely connected. Among previous studies, scientists have found modern people and their Neanderthal relatives shared the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, implying they swapped saliva.

"Probably they were kissing," the researcher noted, explaining that the concept chimed with studies that has found humans of certain genetic backgrounds contain Neanderthal DNA in their genome, revealing interbreeding was occurring.

Intimate Interpretation

"It certainly puts a different perspective on ancient interactions," Brindle commented.

Publishing in the journal Evolution and Human Behavior, the researcher and colleagues detail how, to investigate the historical roots of intimate contact, they first had to develop a definition that was not limited to how humans smooch.

Defining Kissing

"Previously there were some efforts to describe a intimate act, but it's very much been human-centric, which implies that basically non-human species do not engage in this. Now we know that they probably do, it may appear different from what human kissing looks like," explained Brindle.

However, she noted some behaviors that resembled intimate contact were distinct activities – such as the processing and food sharing, or "kiss-fighting", observed in fish known as certain marine animals.

Consequently the team came up with a description of kissing centered around friendly interactions involving directed oral interaction with a individual of the identical group, with some movement of the oral area but absence of nutrition.

Research Approach

The lead researcher said they focused on accounts of kissing in non-human species from Africa and Asian regions, including primates, apes and great apes, and employed online videos to verify the reports.

Scientists then integrated this information with details on the genetic connections between living and ancient types of such animals.

Evolutionary Origins

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

Placement of ancient hominins on this evolutionary lineage means it is probable they, too, engaged in a kiss, the scientists conclude. But the activity may not have been limited to their own species.

"The fact that modern people engage intimately, the fact that we now have demonstrated that ancient relatives very likely kissed, indicates that the both groups are probably did kissed," the researcher noted.

Evolutionary Importance

While the evolutionary explanation is debated, Brindle said kissing could be used in reproductive situations to potentially enhance mating outcomes or help choose between partners, while it could assist strengthen connections when used in a non-sexual manner.

A separate researcher in the activities of primates said that as kissing behavior was seen in a wide range of primates it made sense its origins lie deep in our evolutionary past, and an examination of different forms of kissing among a wider variety of species might extend its beginnings back even earlier still.

"Behaviors that we consider as signatures of our species, like intimate contact, are not unique to us if we examine carefully at other animals," the expert noted.

Cultural Aspects

An archaeology expert said that intimate contact had a social component as it was not common to all human groups.

"Nonetheless, as people we thrive or fail on the quality of our emotional bonds, and methods of promoting trust and intimacy will have been important for millions of years," the professor stated. "This could represent an concept that appears a bit contradictory to our incorrect assumptions of a supposedly aggressive and ancient history, but really it should be expected that Neanderthals – and even Neanderthals and our own species collectively – engaged intimately."