Neanderthals and Modern Humans Were Likely Kissing, Researchers Suggest
From Galápagos albatrosses to polar bears, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Now, researchers propose that ancient hominins also engaged in this behavior – and possibly locked lips with early Homo sapiens.
Common Microbial Clues
It is not the first time scientists have proposed ancient relatives and Homo sapiens were intimately acquainted. Among previous studies, researchers have found humans and their thick-browed cousins possessed the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, implying they swapped saliva.
"Probably they were kissing," the researcher noted, adding that the idea aligned with research that has revealed people of certain genetic backgrounds have bits of Neanderthal DNA in their genetic makeup, demonstrating interbreeding was at play.
Intimate Spin
"This offers a different spin on human-Neanderthal relations," the lead researcher said.
Publishing in the publication Evolution and Human Behavior, Brindle and her team detail how, to explore the historical roots of kissing, they first had to come up with a definition that was not limited to how humans smooch.
Defining Kissing
"Previously there were some efforts to describe a intimate act, but it's largely focused on humans, which means that basically non-human species do not engage in this. Currently we know that they probably do, it might just not look from what human kissing looks like," explained the evolutionary biologist.
Nonetheless, she said some actions that looked like kissing were distinct activities – such as the processing and transfer of food, or "mouth contact", seen in fish called certain marine animals.
As a result the team came up with a description of intimate contact centered around social behaviors involving intentional mouth-to-mouth contact with a individual of the same species, with some motion of the mouth but absence of food.
Study Approach
The lead researcher said they concentrated on accounts of kissing in primates from Africa and Asia, including primates, apes and great apes, and employed online videos to confirm the observations.
The researchers then combined this data with details on the evolutionary relationships between extant and extinct species of such primates.
Historical Origins
The team say the findings suggest kissing evolved somewhere between 21.5m and 16.9 million years ago in the ancestors of the large apes.
Placement of Neanderthals on this family tree means it is likely they, too, engaged in a intimate act, the scientists conclude. But the behavior may not have been confined to their specific group.
"Reality that humans engage intimately, the fact that we currently have shown that ancient relatives very likely engaged, suggests that the two [species] are also likely to have kissed," Brindle added.
Biological Importance
Although the evolutionary explanation is discussed, the expert explained intimate contact could be used in sexual contexts to possibly increase mating outcomes or assist in selecting between mates, while it could assist strengthen connections when used in a non-sexual manner.
Another expert in the activities of great apes commented that as kissing behavior was seen in a wide range of primates it was logical its roots extend far into our evolutionary past, and an analysis of different forms of intimate behavior among a broader range of species might extend its origins back even earlier still.
"Behaviors that we consider as signatures of human life, like intimate contact, are not exclusive to us if we look closely at different species," he said.
Social Aspects
An archaeology expert said that intimate contact had a cultural element as it was not common to all human groups.
"However, as humans we thrive or fail on the strength of our relationships, and ways of promoting confidence and closeness will have been important for millions of years," she said. "It might be an concept that appears a bit contradictory to our incorrect assumptions of a supposedly aggressive and ancient history, but really it ought to be expected that ancient hominins – and even them and our human ancestors together – engaged intimately."