🔗 Share this article

From Galápagos albatrosses to Arctic mammals, primates to orangutans, various animals appear to kiss. Now, scientists suggest that ancient hominins did it too – and possibly locked lips with modern humans.

Common Oral Evidence

It is not the first time experts have suggested Neanderthals and Homo sapiens were closely connected. Among previous studies, scientists have discovered humans and their thick-browed cousins possessed the identical oral bacteria for hundreds of thousands of years after the two species split, suggesting they exchanged oral fluids.

"Likely they were engaging in intimate contact," the researcher noted, explaining that the concept aligned with research that has revealed people of certain genetic backgrounds contain ancient genetic material in their genome, revealing genetic mixing was occurring.

Romantic Spin

"This offers a different perspective on human-Neanderthal relations," Brindle said.

Writing in the journal a scientific periodical, the researcher and colleagues report how, to investigate the evolutionary origins of intimate contact, they first had to develop a definition that was not limited to how humans smooch.

Describing Kissing

"Previously there were some previous attempts to define a intimate act, but it's very much been focused on humans, which means that essentially non-human species do not engage in this. Now we know that they probably do, it may appear different from what our intimate contact resembles," explained Brindle.

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

Consequently the team came up with a definition of kissing centered around social behaviors involving directed oral interaction with a member of the identical group, with some movement of the oral area but no transfer of food.

Study Methods

Brindle said they focused on reports of kissing in non-human species from the African continent and Asia, including primates, apes and great apes, and employed online videos to verify the reports.

The researchers then combined this information with information on the evolutionary relationships between extant and extinct species of such primates.

Historical Timeline

Researchers say the findings indicate kissing developed approximately 21.5 million and 16.9 million years ago in the predecessors of the large apes.

Placement of ancient hominins on this family tree means it is probable they, too, engaged in a intimate act, the researchers say. But the activity might not have been confined to their specific group.

"The fact that humans engage intimately, the reality that we now have shown that Neanderthals probably engaged, indicates that the both groups are also likely to have engage," Brindle noted.

Biological Significance

Although the scientific reasoning is debated, Brindle said intimate contact could be employed in sexual contexts to potentially increase reproductive success or help choose between partners, while it might help reinforce bonding when used in a platonic way.

Another expert in the behavior of great apes 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 various types of intimate behavior among a broader range of animals might push its origins back even earlier still.

"Behaviors that we think of as characteristics of human life, like kissing, are not unique to us if we examine carefully at different species," he said.

Social Aspects

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

"Nonetheless, as people we succeed or struggle on the quality of our emotional bonds, and ways of promoting trust and intimacy will have been significant for millions of years," the professor stated. "This could represent an image that seems a bit incongruous to our incorrect assumptions of a rather ruthless and ancient history, but really it ought to be expected that Neanderthals – and including them and our own species collectively – kissed."