Ancient Hominins and Modern Humans Were Likely Kissing, Researchers Suggest

Among Galápagos albatrosses to Arctic mammals, chimpanzees to orangutans, various animals appear to kiss. Currently, scientists suggest that Neanderthals also engaged in this behavior – and possibly exchanged kisses with modern humans.

Shared Microbial Evidence

It is not the first time scientists have suggested ancient relatives and early modern humans were intimately acquainted. Among previous studies, researchers have discovered modern people and their Neanderthal relatives possessed the same mouth microbe for millions of years after the two species split, suggesting they exchanged oral fluids.

"Probably they were engaging in intimate contact," the researcher noted, adding that the concept chimed with studies that has revealed humans of non-African ancestry have bits of Neanderthal DNA in their genetic makeup, revealing interbreeding was occurring.

Romantic Interpretation

"It certainly puts a different spin on human-Neanderthal relations," Brindle said.

Publishing in the publication Evolution and Human Behavior, the researcher and colleagues report how, to investigate the evolutionary origins of intimate contact, they first had to come up with a description 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 means that essentially other animals don't kiss. Currently we understand that they likely engage, it might just not look from what our intimate contact looks like," explained Brindle.

Nonetheless, she noted some behaviors that looked like intimate contact were something rather different – such as the processing and food sharing, or "kiss-fighting", observed in fish called certain marine animals.

Consequently the research group developed a description of kissing based on social behaviors involving intentional oral interaction with a individual of the same species, with some movement of the mouth but absence of food.

Study Approach

Brindle said they focused on accounts of kissing in non-human species from the African continent and Asian regions, including bonobos, chimpanzees and great apes, and employed online videos to verify the reports.

The researchers then integrated this information with information on the genetic connections between living and ancient types of such primates.

Evolutionary Timeline

The team propose the findings indicate intimate contact developed somewhere between 21.5 million and 16.9 million years ago in the ancestors of the great primates.

The position of Neanderthals on this evolutionary lineage suggests it is likely they, too, indulged in a kiss, the scientists conclude. But the activity may not have been limited to their specific group.

"The fact that humans kiss, the reality that we currently have shown that Neanderthals very likely kissed, suggests that the both groups are probably did engage," Brindle added.

Evolutionary Importance

Although the evolutionary explanation is debated, the expert said kissing could be employed in sexual contexts to possibly increase reproductive success or assist in selecting between mates, while it could assist strengthen connections when used in a platonic way.

Another expert in the activities of primates said that as intimate contact was observed in a broad spectrum of apes it was logical its roots lie deep in our ancient history, and an analysis of various types 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 kissing, are not unique to us if we look closely at other animals," he said.

Social Aspects

Another professor explained 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 emotional bonds, and methods of promoting trust and intimacy 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 expected that ancient hominins – and even Neanderthals and our human ancestors together – engaged intimately."