🔗 Share this article

From seabirds to Arctic mammals, chimpanzees to orangutans, certain species appear to kiss. Currently, scientists suggest that Neanderthals also engaged in this behavior – and possibly locked lips with early Homo sapiens.

Common Oral Clues

It is not the first time experts have suggested ancient relatives and early modern humans were closely connected. In previous studies, researchers have found modern people and their thick-browed cousins possessed the identical oral bacteria for millions of years after the two species split, suggesting they swapped saliva.

"Likely they were engaging in intimate contact," the researcher noted, explaining that the concept chimed with studies that has revealed humans of certain genetic backgrounds contain Neanderthal DNA in their genome, demonstrating genetic mixing was at play.

Intimate Interpretation

"This offers a more romantic perspective on ancient interactions," the lead researcher commented.

Publishing in the journal a scientific periodical, Brindle and colleagues report how, to investigate the evolutionary origins of intimate contact, they first had to come up with a description that was not restricted by how humans kiss.

Defining Kissing

"Previously there were some efforts to define a kiss, but it's very much been human-centric, which means that essentially non-human species don't kiss. Now we understand that they probably do, it may appear different from what our intimate contact resembles," said Brindle.

Nonetheless, she said some behaviors that looked like kissing were something rather different – such as the processing and food sharing, or "mouth contact", observed in fish called French grunts.

As a result the research group developed a definition of kissing centered around social behaviors involving intentional mouth-to-mouth contact with a member of the identical group, with some motion of the oral area but absence of food.

Research Methods

The lead researcher said they focused on reports of kissing in primates from the African continent and Asia, including primates, apes and great apes, and employed digital recordings to confirm the observations.

Scientists then combined this information with details on the genetic connections between extant and ancient species of such primates.

Historical Origins

Researchers say the findings indicate intimate contact developed somewhere between 21.5 million and 16.9 million years ago in the ancestors of the large apes.

Placement of Neanderthals on this family tree suggests it is probable they, too, engaged in a kiss, the scientists conclude. But the behavior might not have been limited to their own species.

"The fact that modern people engage intimately, the reality that we now have demonstrated that ancient relatives probably engaged, suggests that the two [species] are probably did kissed," the researcher noted.

Evolutionary Significance

While the evolutionary explanation is discussed, the expert explained kissing could be employed in reproductive situations to potentially increase reproductive success or help choose between partners, while it might help strengthen connections when practiced in a non-sexual manner.

Another expert in the activities of great apes commented that as kissing behavior was observed in a wide range of apes it made sense its roots extend far into our ancient history, and an analysis of different forms of intimate behavior among a broader range of animals might extend its beginnings back even earlier still.

"Things that we think of as characteristics of human life, like intimate contact, are not unique to us if we examine carefully at other animals," he said.

Social Aspects

Another professor said that intimate contact had a social component as it was not common to all human groups.

"However, as humans we thrive or fail on the strength of our emotional bonds, and methods of encouraging confidence and intimacy will have been important for millions of years," she said. "It might be an image that appears a bit contradictory to our misplaced ideas of a rather ruthless and aggressive past, but really it should be expected that ancient hominins – and even Neanderthals and our own species together – kissed."