Ancient Hominins and Modern Humans Were Likely Engaging in Intimate Contact, Scientists Propose
Among seabirds to Arctic mammals, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Now, scientists propose that ancient hominins also engaged in this behavior – and possibly locked lips with modern humans.
Common Oral Clues
It is not the first time experts have suggested ancient relatives and early modern humans were closely connected. In earlier research, 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 exchanged oral fluids.
"Probably they were engaging in intimate contact," she said, adding that the concept chimed with studies that has found humans of certain genetic backgrounds have bits of Neanderthal DNA in their genetic makeup, revealing interbreeding was occurring.
Intimate Spin
"This offers a more romantic spin on human-Neanderthal relations," Brindle commented.
Publishing in the publication Evolution and Human Behavior, Brindle and her team report how, to investigate the evolutionary origins of kissing, they first had to develop a definition that was not limited to how people smooch.
Defining Intimate Contact
"Previously there were some efforts to describe a intimate act, but it's largely human-centric, which means that essentially other animals do not engage in this. Currently we know that they probably do, it might just not look from what our intimate contact looks like," said the evolutionary biologist.
Nonetheless, she noted some behaviors that looked like intimate contact were something rather different – such as the chewing and food sharing, or "kiss-fighting", observed in fish called French grunts.
Consequently the research group developed a description of intimate contact based on social behaviors involving directed mouth-to-mouth contact with a member of the identical group, with some motion of the oral area but absence of nutrition.
Study Approach
The lead researcher explained they concentrated on reports of kissing in non-human species from Africa and Asia, including primates, chimpanzees and orangutans, and employed online videos to verify the observations.
Scientists then combined this information with information on the evolutionary relationships between living and ancient types of such animals.
Historical Origins
The team say the findings suggest intimate contact evolved approximately 21.5 million and 16.9m years ago in the predecessors of the large apes.
Placement of ancient hominins on this family tree means it is probable they, too, indulged in a kiss, the scientists say. But the behavior might not have been confined to their specific group.
"The fact that modern people kiss, the fact that we currently have demonstrated that ancient relatives probably kissed, suggests that the two [species] are probably did kissed," the researcher added.
Evolutionary Importance
While the scientific reasoning is debated, Brindle explained kissing could be employed in reproductive situations to possibly enhance reproductive success or help choose between partners, while it might help reinforce bonding when used in a non-sexual manner.
Another expert in the behavior of great apes commented that as intimate contact was seen in a wide range of apes it made sense its roots lie deep in our evolutionary past, and an examination of different forms of kissing among a broader range of animals might extend its beginnings back even earlier still.
"Things that we consider as signatures of human life, like intimate contact, are not exclusive 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 universal to all societies.
"Nonetheless, as people we thrive or fail on the strength of our relationships, and methods of encouraging confidence and intimacy will have been important for eons," she said. "This could represent an concept that seems a bit incongruous to our incorrect assumptions of a rather ruthless and aggressive past, but really it ought to be no surprise that ancient hominins – and even Neanderthals and our own species together – engaged intimately."
