Neanderthals and Early Humans Were Likely Engaging in Intimate Contact, Scientists Suggest

Among seabirds to Arctic mammals, primates to great apes, certain species engage in mouth-to-mouth contact. Currently, scientists propose that ancient hominins did it too – and might even have exchanged kisses with early Homo sapiens.

Common Oral Evidence

It is not the first time experts have proposed Neanderthals and early modern humans were closely connected. Among earlier research, scientists have found humans and their thick-browed cousins shared the identical oral bacteria for hundreds of thousands of years after the two species split, suggesting they swapped saliva.

"Likely they were kissing," she said, adding that the idea chimed with research that has revealed people of certain genetic backgrounds have bits of ancient genetic material in their genetic makeup, revealing interbreeding was at play.

Romantic Spin

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

Publishing in the journal a scientific periodical, the researcher and her team detail how, to explore the evolutionary origins of kissing, they first had to develop a description that was not restricted by how people kiss.

Describing Kissing

"There have been some previous attempts to define a kiss, but it's very much been focused on humans, which implies that basically non-human species do not engage in this. Currently we know that they probably do, it may appear different from what human kissing looks like," said the evolutionary biologist.

However, she noted some actions that looked like kissing were something rather different – such as the processing and food sharing, or "mouth contact", seen in aquatic species called certain marine animals.

Consequently the team developed a definition of kissing based on friendly interactions involving intentional mouth-to-mouth contact with a individual of the same species, with some motion of the oral area but no transfer of nutrition.

Study Approach

Brindle explained they concentrated on accounts of kissing in non-human species from the African continent and Asia, including bonobos, chimpanzees and orangutans, and used online videos to confirm the observations.

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

Evolutionary Origins

The team say the results suggest intimate contact developed somewhere between 21.5 million and 16.9 million years ago in the predecessors of the great primates.

The position of ancient hominins on this evolutionary lineage suggests it is probable they, too, indulged in a kiss, the scientists conclude. But the behavior may not have been limited to their specific group.

"The fact that modern people engage intimately, the reality that we now have demonstrated that Neanderthals probably kissed, indicates that the two [species] are also likely to have engage," Brindle added.

Biological Importance

Although the scientific reasoning is discussed, Brindle said kissing could be employed in sexual contexts to possibly increase reproductive success or assist in selecting between mates, while it might help strengthen connections when practiced in a non-sexual manner.

Another expert in the activities of primates said that as intimate contact was observed in a wide range of primates it was logical its roots extend far into our ancient history, and an analysis of various types of kissing among a wider variety of animals might extend its beginnings back further still.

"Things that we think of as signatures of our species, like kissing, are not exclusive to us if we examine carefully at different species," he said.

Social Aspects

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

"However, as humans we thrive or fail on the quality of our emotional bonds, and ways of encouraging trust and intimacy will have been significant for millions of years," the professor stated. "It might be an concept that seems a bit contradictory to our misplaced ideas of a rather ruthless and aggressive past, but really it should be expected that Neanderthals – and even Neanderthals and our own species together – engaged intimately."