Ancient Hominins and Modern Humans Were Likely Kissing, Researchers Propose
Among seabirds to Arctic mammals, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Currently, scientists propose that ancient hominins did it too – and possibly exchanged kisses with modern humans.
Shared Microbial Evidence
This isn't the initial instance experts have proposed ancient relatives and early modern humans were closely connected. Among previous studies, researchers have found modern people and their Neanderthal relatives shared the identical oral bacteria for millions of years after the two species split, implying they swapped saliva.
"Likely they were engaging in intimate contact," the researcher noted, adding that the idea aligned with research that has found people of certain genetic backgrounds contain ancient genetic material in their genome, demonstrating genetic mixing was at play.
Intimate Interpretation
"This offers a different perspective on human-Neanderthal relations," Brindle said.
Publishing in the journal Evolution and Human Behavior, the researcher and her team detail how, to explore the historical roots of intimate contact, they first had to come up with a definition that was not restricted by how humans smooch.
Describing Intimate Contact
"There have been some previous attempts to define a intimate act, but it's largely focused on humans, which implies that basically other animals do not engage in this. Now we understand that they probably do, it may appear different from what human kissing resembles," said the evolutionary biologist.
Nonetheless, she noted some actions that resembled kissing were distinct activities – such as the chewing and food sharing, or "kiss-fighting", observed in fish known as French grunts.
As a result the research group came up with a definition of intimate contact centered around social behaviors involving directed oral interaction with a member of the identical group, with some motion of the mouth but absence of nutrition.
Study Methods
The lead researcher said they focused on reports of intimate behavior in primates from Africa and Asia, including primates, apes and orangutans, and employed online videos to verify the reports.
The researchers then integrated this information with details on the evolutionary relationships between extant and extinct types of such primates.
Historical Origins
The team say the findings suggest kissing evolved approximately 21.5m and 16.9m years ago in the ancestors of the large apes.
Placement of Neanderthals on this evolutionary lineage means it is likely they, too, engaged in a intimate act, the scientists conclude. But the activity may not have been confined to their own species.
"The fact that humans engage intimately, the reality that we currently have demonstrated that Neanderthals probably engaged, suggests that the both groups are probably did engage," the researcher noted.
Biological Importance
Although the evolutionary explanation is discussed, Brindle explained kissing could be used in sexual contexts to potentially increase mating outcomes or assist in selecting between mates, while it could assist reinforce bonding when used in a non-sexual manner.
A separate researcher in the activities of primates commented that as kissing behavior was observed in a broad spectrum of apes it made sense its origins extend far into our evolutionary past, and an examination of various types of kissing among a wider variety of species might extend its beginnings back even earlier still.
"Behaviors that we think of as signatures of human life, like kissing, are not unique to us if we examine carefully at other animals," he said.
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 confidence and closeness will have been important for millions of years," she said. "It might be an image that appears a bit contradictory to our incorrect assumptions of a rather ruthless and ancient history, but actually it should be no surprise that ancient hominins – and even Neanderthals and our human ancestors together – kissed."
