Ancient Hominins and Early Humans May Have Kissing, Scientists Suggest

Among Galápagos albatrosses to polar bears, chimpanzees to orangutans, various animals engage in mouth-to-mouth contact. Now, researchers suggest that Neanderthals also engaged in this behavior – and possibly exchanged kisses with early Homo sapiens.

Shared Oral Clues

This isn't the initial instance scientists have proposed Neanderthals and Homo sapiens were closely connected. In earlier research, researchers have discovered modern people and their thick-browed cousins 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 revealed people of non-African ancestry have bits of Neanderthal DNA in their genetic makeup, demonstrating genetic mixing was at play.

Romantic Spin

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

Writing in the publication Evolution and Human Behavior, the researcher and her team report how, to explore the evolutionary origins of intimate contact, they first had to come up with a definition that was not restricted by how people kiss.

Defining Intimate Contact

"Previously there were some previous attempts to describe a intimate act, but it's largely human-centric, which means that essentially other animals don't kiss. Currently we understand that they likely engage, it might just not look from what human kissing resembles," explained the evolutionary biologist.

Nonetheless, she noted some actions that looked like intimate contact were distinct activities – such as the processing and food sharing, or "mouth contact", observed in fish known as certain marine animals.

Consequently the team came up with a definition of intimate contact centered around social behaviors involving directed oral interaction with a member of the same species, with some movement of the mouth but no transfer of nutrition.

Study Methods

Brindle explained they concentrated on reports of intimate behavior in primates from Africa and Asian regions, including bonobos, chimpanzees and great apes, and employed digital recordings to confirm the observations.

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

Evolutionary Origins

The team say the findings suggest kissing developed somewhere between 21.5 million and 16.9 million years ago in the ancestors of the large apes.

Placement of Neanderthals on this evolutionary lineage means it is probable they, too, engaged in a intimate act, the researchers say. 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 shown that ancient relatives very likely kissed, indicates that the both groups are probably did engage," Brindle noted.

Biological Importance

While the evolutionary explanation is discussed, Brindle explained intimate contact could be employed in sexual contexts to potentially increase reproductive success or help choose between mates, while it might help strengthen connections when used in a non-sexual manner.

Another expert in the activities of great apes said that as intimate contact was observed in a broad spectrum of primates it made sense its roots extend far into our evolutionary past, and an analysis of various types of kissing among a broader range of animals might push its beginnings back even earlier still.

"Things that we think of as characteristics of human life, like kissing, are not exclusive to us if we look closely at other animals," he said.

Social Elements

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

"Nonetheless, as humans we thrive or fail on the strength of our relationships, and methods of encouraging confidence and closeness will have been significant for millions of years," the professor stated. "This could represent an image that appears a bit incongruous to our incorrect assumptions of a supposedly aggressive and ancient history, but actually it should be no surprise that Neanderthals – and even Neanderthals and our human ancestors collectively – engaged intimately."