Ancient Hominins and Early Humans Were Likely Engaging in Intimate Contact, Researchers Propose

From seabirds to Arctic mammals, chimpanzees to orangutans, certain species engage in mouth-to-mouth contact. Currently, scientists suggest that Neanderthals also engaged in this behavior – and possibly exchanged kisses with early Homo sapiens.

Common Microbial Clues

This isn't the initial instance experts have proposed ancient relatives and Homo sapiens were closely connected. In previous studies, scientists have discovered modern people and their thick-browed cousins possessed the identical oral bacteria for millions of years after the evolutionary divergence, implying they swapped saliva.

"Likely they were kissing," the researcher noted, adding that the concept chimed with research that has found people of certain genetic backgrounds contain ancient genetic material in their genetic makeup, revealing interbreeding was occurring.

Romantic Spin

"It certainly puts a different spin on ancient interactions," Brindle commented.

Publishing in the publication Evolution and Human Behavior, the researcher and colleagues detail how, to investigate the evolutionary origins of kissing, they first had to develop a definition that was not limited to how people smooch.

Defining Kissing

"Previously there were some efforts to describe a intimate act, but it's very much been human-centric, which implies that basically other animals don't kiss. Now we know that they probably do, it might just not look from what our intimate contact resembles," said the evolutionary biologist.

Nonetheless, she noted some actions that resembled intimate contact were something rather different – such as the chewing and food sharing, or "mouth contact", seen in aquatic species known as French grunts.

Consequently the team came up with a description of intimate contact centered around friendly interactions involving directed oral interaction with a individual of the same species, with some movement of the mouth but absence of nutrition.

Study Methods

The lead researcher said they concentrated on reports of intimate behavior in primates from Africa and Asian regions, including primates, apes and orangutans, and used online videos to confirm the observations.

The researchers then combined this information with details on the genetic connections between extant and extinct species of such primates.

Evolutionary Origins

The team say the results suggest intimate contact evolved somewhere between 21.5m and 16.9m years ago in the predecessors of the great primates.

Placement of Neanderthals on this family tree suggests it is likely they, too, engaged in a kiss, the scientists conclude. But the activity might not have been limited to their own species.

"Reality that modern people engage intimately, the reality that we currently have demonstrated that Neanderthals probably kissed, suggests that the two [species] are also likely to have engage," Brindle added.

Biological Importance

Although the scientific reasoning is discussed, Brindle explained kissing could be used in reproductive situations to potentially enhance mating outcomes or assist in selecting between mates, while it could assist reinforce bonding when used in a platonic way.

Another expert in the behavior of primates said that as intimate contact was observed in a broad spectrum of apes it was logical its roots lie deep in our evolutionary past, and an examination of different forms of kissing among a wider variety of species might extend its beginnings back even earlier still.

"Things that we consider as signatures of our species, like intimate contact, are not unique to us if we examine carefully at other animals," he said.

Social Aspects

An archaeology expert said that kissing had a cultural element as it was not common to all human groups.

"However, as people we thrive or fail on the quality of our emotional bonds, and ways of promoting confidence and closeness will have been important for eons," she said. "It might be an image that appears a bit incongruous to our incorrect assumptions of a supposedly aggressive and aggressive past, but really it ought to be no surprise that ancient hominins – and even them and our own species together – kissed."