Among seabirds to Arctic mammals, chimpanzees to orangutans, various animals engage in mouth-to-mouth contact. Now, scientists propose that ancient hominins did it too – and possibly exchanged kisses with early Homo sapiens.
It is not the first time scientists have suggested ancient relatives and early modern humans were intimately acquainted. In earlier research, scientists have found humans and their thick-browed cousins possessed the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, implying they exchanged oral fluids.
"Likely they were kissing," the researcher noted, explaining that the concept aligned with research that has revealed people of non-African ancestry contain ancient genetic material in their genetic makeup, revealing interbreeding was at play.
"This offers a different perspective on ancient interactions," the lead researcher said.
Writing in the journal a scientific periodical, Brindle and colleagues detail how, to investigate the evolutionary origins of kissing, they first had to develop a definition that was not restricted by how people kiss.
"There have been some efforts to define a kiss, but it's largely human-centric, which means that basically non-human species do not engage in this. Currently we understand that they probably do, it might just not look from what our intimate contact looks like," said Brindle.
Nonetheless, she said some behaviors that looked like kissing were distinct activities – such as the processing and food sharing, or "kiss-fighting", observed in fish known as French grunts.
As a result the team developed a description of kissing centered around friendly interactions involving directed mouth-to-mouth contact with a member of the identical group, with some movement of the mouth but no transfer of nutrition.
Brindle explained they concentrated on reports of kissing in primates from Africa and Asia, including primates, apes and orangutans, and used online videos to confirm the observations.
Scientists then integrated this data with information on the genetic connections between living and extinct species of such primates.
Researchers say the results suggest kissing evolved approximately 21.5m and 16.9 million years ago in the predecessors of the large apes.
The position of Neanderthals on this evolutionary lineage means it is likely they, too, indulged in a kiss, the researchers conclude. But the activity might not have been limited to their specific group.
"Reality that humans engage intimately, the fact that we currently have demonstrated that ancient relatives very likely kissed, suggests that the two [species] are probably did kissed," the researcher added.
While the scientific reasoning is discussed, the expert said intimate contact could be employed in sexual contexts to potentially enhance mating outcomes or assist in selecting between partners, while it might help strengthen connections when practiced in a non-sexual manner.
A separate researcher in the activities of great apes commented that as intimate contact was observed in a broad spectrum of apes it was logical its roots extend far into our evolutionary past, and an analysis of various types of intimate behavior among a wider variety of animals might extend its beginnings back further still.
"Behaviors that we think of as signatures of our species, like intimate contact, are not unique to us if we look closely at different species," the expert noted.
Another professor said that intimate contact had a cultural element as it was not universal to all human groups.
"Nonetheless, as humans we succeed or struggle on the quality of our relationships, and ways of encouraging trust and intimacy will have been important for eons," the professor stated. "This could represent an concept that appears a bit contradictory to our misplaced ideas of a rather ruthless and ancient history, but actually it should be no surprise that Neanderthals – and even them and our human ancestors collectively – engaged intimately."
Elara Vance is a dedicated MapleStory enthusiast and gaming writer, known for creating in-depth guides and staying updated on game mechanics.
