Neanderthals and Modern Humans May Have Kissing, Scientists Propose

Among seabirds to Arctic mammals, primates to great apes, certain species engage in mouth-to-mouth contact. Currently, researchers suggest that Neanderthals also engaged in this behavior – and possibly exchanged kisses with early Homo sapiens.

Shared Microbial Evidence

It is not the first time scientists have proposed Neanderthals and early modern humans were closely connected. Among previous studies, researchers have discovered humans and their Neanderthal relatives possessed the same mouth microbe for hundreds of thousands of years after the two species split, implying they exchanged oral fluids.

"Likely they were engaging in intimate contact," she said, explaining that the idea aligned with research that has found humans of non-African ancestry have bits of ancient genetic material in their genome, revealing genetic mixing was at play.

Romantic Interpretation

"This offers a different perspective on ancient interactions," the lead researcher said.

Publishing in the publication Evolution and Human Behavior, Brindle and her team detail how, to explore the evolutionary origins of kissing, they first had to come up with a description that was not limited to how humans smooch.

Defining Kissing

"There have been some previous attempts to describe a intimate act, but it's very much been focused on humans, which implies that essentially non-human species do not engage in this. Currently we know that they likely engage, it might just not look from what our intimate contact resembles," explained Brindle.

However, she said some behaviors that looked like intimate contact were something rather different – such as the processing and food sharing, or "mouth contact", seen in fish called certain marine animals.

As a result the research group came up with a description of kissing based on friendly interactions involving directed mouth-to-mouth contact with a individual of the same species, with some movement of the mouth but no transfer of food.

Research Approach

Brindle said they focused on accounts of intimate behavior in non-human species from Africa and Asia, including primates, apes and orangutans, and employed online videos to confirm the observations.

Scientists then combined this information with information on the evolutionary relationships between living and ancient species of such primates.

Evolutionary Timeline

The team propose the findings suggest intimate contact evolved approximately 21.5m and 16.9m years ago in the ancestors of the large apes.

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

"The fact that humans kiss, the fact that we now have shown that ancient relatives probably engaged, suggests that the both groups are also likely to have engage," the researcher noted.

Biological Significance

While the evolutionary explanation is discussed, Brindle said kissing could be employed in sexual contexts to possibly increase reproductive success or help choose between mates, while it might help strengthen connections when practiced in a platonic way.

Another expert in the behavior of primates commented that as kissing behavior was observed in a broad spectrum of apes it was logical its roots extend far into our evolutionary past, and an examination of various types of intimate behavior among a wider variety of species might extend its origins back further still.

"Behaviors that we think of as characteristics of human life, like intimate contact, are not unique to us if we examine carefully at other animals," he said.

Cultural Aspects

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

"Nonetheless, as people we thrive or fail on the quality of our emotional bonds, and ways of promoting trust and closeness will have been important for eons," she said. "This could represent an concept that appears a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but really it should be expected that ancient hominins – and including them and our own species together – engaged intimately."