Ancient Hominins and Early Humans Were Likely Kissing, Scientists Propose
Among Galápagos albatrosses to polar bears, chimpanzees to orangutans, various animals appear to kiss. Now, researchers propose that ancient hominins did it too – and might even have exchanged kisses with modern humans.
Common Microbial Clues
It is not the first time experts have suggested Neanderthals and Homo sapiens were intimately acquainted. In earlier research, scientists have found humans and their Neanderthal relatives possessed the identical oral bacteria for hundreds of thousands of years after the two species split, implying they swapped saliva.
"Probably they were engaging in intimate contact," the researcher noted, explaining that the concept aligned with studies that has found humans of certain genetic backgrounds have bits of ancient genetic material in their genetic makeup, demonstrating interbreeding was at play.
Intimate Interpretation
"It certainly puts a different spin on ancient interactions," Brindle commented.
Writing in the publication Evolution and Human Behavior, Brindle 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 limited to how humans kiss.
Defining Kissing
"Previously there were some previous attempts to describe a intimate act, but it's largely human-centric, which implies that basically non-human species don't kiss. Currently we know that they probably do, it may appear different from what our intimate contact looks like," explained the evolutionary biologist.
However, she said some actions that resembled intimate contact were distinct activities – such as the processing and food sharing, or "kiss-fighting", seen in fish called certain marine animals.
As a result the team came up with a description of intimate contact based on social behaviors involving directed oral interaction with a individual of the identical group, with some movement of the oral area but no transfer of food.
Research Methods
The lead researcher explained they focused on accounts of intimate behavior in primates from Africa and Asia, including primates, apes and great apes, and employed online videos to confirm the reports.
Scientists then combined this data with information on the evolutionary relationships between extant and ancient species of such animals.
Evolutionary Origins
Researchers propose the results suggest intimate contact evolved somewhere between 21.5m and 16.9m years ago in the predecessors of the great primates.
The position of ancient hominins on this evolutionary lineage suggests it is probable they, too, engaged in a intimate act, the scientists conclude. But the activity might not have been limited to their own species.
"The fact that humans engage intimately, the reality that we now have demonstrated that ancient relatives very likely kissed, suggests that the two [species] are also likely to have kissed," the researcher added.
Evolutionary Importance
Although the evolutionary explanation is discussed, the expert said intimate contact could be used in reproductive situations to potentially increase reproductive success or assist in selecting between mates, while it might help reinforce bonding when practiced in a platonic way.
Another expert in the activities of primates commented that as kissing behavior was seen in a wide range of apes it was logical its roots lie deep in our ancient history, and an examination of different forms of kissing among a wider variety of animals might push its origins back even earlier still.
"Things that we think of as signatures of our species, like intimate contact, are not exclusive to us if we examine carefully at other animals," he said.
Social Elements
Another professor explained that kissing had a social component as it was not universal to all societies.
"Nonetheless, as humans we thrive or fail on the strength of our relationships, and ways of promoting trust and closeness will have been important for millions of years," the professor stated. "It might be an concept that seems a bit contradictory to our incorrect assumptions of a rather ruthless and aggressive past, but actually it ought to be no surprise that ancient hominins – and even them and our own species collectively – kissed."
