🔗 Share this article

From Galápagos albatrosses to polar bears, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Now, researchers propose that ancient hominins did it too – and possibly locked lips with modern humans.

Shared Microbial Evidence

It is not the first time experts have suggested Neanderthals and early modern humans were closely connected. Among earlier research, scientists have discovered modern people and their Neanderthal relatives shared the same mouth microbe for hundreds of thousands of years after the two species split, suggesting they swapped saliva.

"Probably they were engaging in intimate contact," she said, explaining that the concept chimed with studies that has found people of non-African ancestry contain Neanderthal DNA in their genome, revealing interbreeding was at play.

Romantic Interpretation

"This offers a different spin on ancient interactions," the lead researcher commented.

Publishing in the publication Evolution and Human Behavior, Brindle and colleagues detail how, to explore the historical roots of intimate contact, they first had to develop a definition that was not limited to how people smooch.

Describing Intimate Contact

"Previously there were some previous attempts to describe a kiss, but it's largely human-centric, which implies that essentially other animals do not engage in this. Now we know that they probably do, it might just not look from what our intimate contact resembles," explained Brindle.

However, she said some actions that resembled intimate contact were something rather different – such as the processing and food sharing, or "mouth contact", observed in fish known as French grunts.

Consequently the research group came up with a definition of intimate contact centered around social behaviors involving intentional mouth-to-mouth contact with a individual of the identical group, with some motion of the oral area but no transfer of nutrition.

Research Methods

The lead researcher said they focused on reports of kissing in primates from Africa and Asian regions, including bonobos, chimpanzees and orangutans, and used digital recordings to confirm the observations.

Scientists then combined this information with information on the genetic connections between extant and extinct types of such primates.

Evolutionary Origins

The team propose the findings indicate kissing evolved somewhere between 21.5m and 16.9 million years ago in the predecessors of the great primates.

Placement of Neanderthals on this family tree suggests it is probable they, too, engaged in a intimate act, the scientists conclude. But the behavior might not have been confined to their specific group.

"The fact that modern people kiss, the reality that we now have demonstrated that Neanderthals probably kissed, indicates that the two [species] are probably did engage," Brindle noted.

Biological Importance

Although the evolutionary explanation is debated, the expert explained intimate contact could be employed in sexual contexts to possibly increase reproductive success or assist in selecting between partners, while it could assist strengthen connections when used in a non-sexual manner.

Another expert in the activities of primates said 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 various types of kissing among a broader range of species might extend its origins back even earlier still.

"Behaviors that we think of as signatures of our species, like intimate contact, are not unique to us if we look closely at different species," he said.

Social Elements

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

"Nonetheless, as people we thrive or fail on the quality of our emotional bonds, and methods of promoting trust and closeness will have been important for eons," she said. "It might be an concept that appears a bit contradictory to our misplaced ideas of a rather ruthless and ancient history, but really it ought to be expected that ancient hominins – and including Neanderthals and our human ancestors together – engaged intimately."