🔗 Share this article

Among Galápagos albatrosses to polar bears, primates to orangutans, certain species engage in mouth-to-mouth contact. Currently, researchers suggest that Neanderthals also engaged in this behavior – and possibly locked lips with early Homo sapiens.

Shared Microbial Clues

It is not the first time scientists have proposed ancient relatives and Homo sapiens were closely connected. Among earlier research, researchers have found humans and their Neanderthal relatives shared the same mouth microbe for millions of years after the evolutionary divergence, suggesting they swapped saliva.

"Probably they were kissing," she said, explaining that the idea chimed with research that has found humans of non-African ancestry have bits of Neanderthal DNA in their genetic makeup, revealing interbreeding was occurring.

Intimate Interpretation

"This offers a more romantic spin on human-Neanderthal relations," the lead researcher commented.

Publishing in the journal a scientific periodical, the researcher and her team report how, to investigate the historical roots of intimate contact, they first had to develop a definition that was not limited to how humans kiss.

Defining Kissing

"Previously there were some efforts to describe a kiss, but it's largely focused on humans, which means that essentially non-human species do not engage in this. Now we know that they likely engage, it may appear different from what human kissing looks like," said Brindle.

Nonetheless, she said some behaviors that looked like kissing were distinct activities – such as the processing and food sharing, or "mouth contact", seen in fish known as French grunts.

As a result the team developed a description of intimate contact based on social behaviors involving intentional oral interaction with a member of the identical group, with some movement of the mouth but no transfer of nutrition.

Study Approach

Brindle explained they concentrated on reports of intimate behavior in non-human species from the African continent and Asia, including bonobos, apes and orangutans, and used online videos to verify the reports.

The researchers then combined this data with information on the genetic connections between living and extinct types of such primates.

Historical Timeline

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

Placement of ancient hominins on this evolutionary lineage suggests it is likely they, too, indulged in a intimate act, the scientists conclude. But the activity may not have been limited to their specific group.

"The fact that modern people engage intimately, the fact that we currently have demonstrated that Neanderthals probably engaged, indicates that the both groups are probably did engage," the researcher noted.

Evolutionary Importance

While the evolutionary explanation 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 reinforce bonding when practiced in a non-sexual manner.

Another expert in the activities of great apes commented that as intimate contact was observed 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 beginnings back further still.

"Things that we consider as signatures of our species, like kissing, are not unique to us if we look closely at other animals," the expert noted.

Social Aspects

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

"However, as people we succeed or struggle on the strength of our relationships, and ways of encouraging trust and intimacy will have been significant for millions of years," she said. "This could represent an concept that seems a bit incongruous to our misplaced ideas of a rather ruthless and aggressive past, but really it ought to be no surprise that ancient hominins – and including them and our human ancestors collectively – engaged intimately."