Ancient Hominins and Early Humans May Have Kissing, Researchers Suggest

Among Galápagos albatrosses to Arctic mammals, chimpanzees to orangutans, certain species appear to kiss. Now, researchers suggest that ancient hominins did it too – and might even have exchanged kisses with early Homo sapiens.

Shared Oral Clues

It is not the first time scientists have suggested Neanderthals and Homo sapiens were intimately acquainted. Among previous studies, scientists have discovered humans and their Neanderthal relatives possessed the identical oral bacteria for hundreds of thousands of years after the two species split, suggesting they exchanged oral fluids.

"Probably they were kissing," she said, adding that the concept aligned with research that has found humans of non-African ancestry have bits of Neanderthal DNA in their genetic makeup, revealing genetic mixing was at play.

Romantic Spin

"It certainly puts a more romantic spin on ancient interactions," the lead researcher said.

Writing in the journal Evolution and Human Behavior, Brindle and her team report how, to explore the evolutionary origins of kissing, they first had to come up with a description that was not restricted by how humans kiss.

Describing Intimate Contact

"There have been some previous attempts to describe a kiss, but it's very much been human-centric, which means that essentially non-human species don't kiss. Now we understand that they likely engage, it may appear different from what our intimate contact looks like," explained the evolutionary biologist.

Nonetheless, she noted some behaviors that resembled intimate contact were distinct activities – such as the chewing and transfer of food, or "mouth contact", observed in aquatic species known as certain marine animals.

As a result the team developed a definition of intimate contact centered around social behaviors involving directed mouth-to-mouth contact with a member of the identical group, with some movement of the mouth but no transfer of nutrition.

Study Methods

The lead researcher explained they focused on reports of intimate behavior in non-human species from Africa and Asian regions, including bonobos, chimpanzees and great apes, and used digital recordings to confirm the reports.

Scientists then integrated this information with details on the evolutionary relationships between living and extinct types of such primates.

Historical Origins

Researchers propose the results suggest kissing developed approximately 21.5 million and 16.9m years ago in the predecessors of the large apes.

The position of ancient hominins on this evolutionary lineage suggests it is probable they, too, engaged in a kiss, the researchers say. But the behavior might not have been confined to their specific group.

"The fact that humans kiss, the reality that we currently have shown that ancient relatives very likely engaged, suggests that the two [species] are also likely to have engage," the researcher noted.

Biological Significance

While the scientific reasoning is discussed, the expert said kissing could be used in reproductive situations to possibly increase reproductive success or help choose between mates, while it might help strengthen connections when used in a non-sexual manner.

Another expert in the behavior of primates commented that as intimate contact was observed in a broad spectrum of primates it made sense its roots extend far into our ancient history, and an analysis of different forms of intimate behavior among a broader range of species might push its origins back even earlier still.

"Things that we consider as characteristics of human life, like intimate contact, are not exclusive to us if we look closely at other animals," the expert noted.

Social Aspects

Another professor explained that kissing had a social component as it was not common to all human groups.

"Nonetheless, as humans we succeed or struggle on the strength of our relationships, and ways of encouraging confidence and closeness will have been significant for millions of years," she said. "This could represent an concept that appears a bit contradictory to our misplaced ideas of a supposedly aggressive and ancient history, but really it should be no surprise that Neanderthals – and even them and our human ancestors collectively – engaged intimately."