Ancient Hominins and Modern Humans Were Likely Engaging in Intimate Contact, Scientists Suggest

From seabirds to Arctic mammals, primates to orangutans, various animals engage in mouth-to-mouth contact. Currently, scientists suggest that ancient hominins also engaged in this behavior – and might even have exchanged kisses with modern humans.

Shared Oral Clues

This isn't the initial instance scientists have proposed ancient relatives and early modern humans were closely connected. In earlier research, scientists have found modern people and their Neanderthal relatives shared the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, 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 people of non-African ancestry have bits of Neanderthal DNA in their genome, demonstrating interbreeding was at play.

Romantic Spin

"This offers a different spin on human-Neanderthal relations," the lead researcher commented.

Writing in the journal a scientific periodical, Brindle and her team detail how, to explore the historical roots of kissing, they first had to develop a description that was not restricted by how people smooch.

Defining Kissing

"There have been some previous attempts to define a kiss, but it's largely focused on humans, which means that essentially non-human species do not engage in this. Now we understand that they likely engage, it may appear different from what our intimate contact resembles," said the evolutionary biologist.

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

As a result the research group came up with a definition of intimate contact based on friendly interactions involving intentional oral interaction with a individual of the identical group, with some movement of the mouth but no transfer of nutrition.

Research Methods

The lead researcher said they focused on reports of kissing in non-human species from Africa and Asia, including primates, chimpanzees and orangutans, and used online videos to confirm the reports.

The researchers then combined this information with information on the genetic connections between extant and extinct types of such animals.

Evolutionary Origins

The team propose the findings indicate kissing evolved somewhere between 21.5m and 16.9m years ago in the ancestors of the large apes.

The position of ancient hominins on this family tree suggests it is probable they, too, indulged in a kiss, the scientists conclude. But the activity might not have been limited to their own species.

"Reality that humans kiss, the fact that we now have demonstrated that ancient relatives probably engaged, suggests that the two [species] are probably did kissed," the researcher added.

Evolutionary Importance

Although the scientific reasoning is debated, the expert explained kissing could be used in reproductive situations to possibly increase mating outcomes or help choose between mates, while it might help reinforce bonding when used in a platonic way.

Another expert in the behavior of primates commented that as intimate contact was seen in a wide range of primates it made sense its origins lie deep in our ancient history, and an analysis of different forms of intimate behavior among a broader range of species might push its origins back further still.

"Behaviors that we think of as characteristics of human life, like intimate contact, are not exclusive to us if we look closely at different species," the expert noted.

Social Elements

Another professor said that intimate contact had a social component as it was not universal to all societies.

"However, as humans we succeed or struggle on the strength of our emotional bonds, and methods of promoting trust and closeness will have been significant for eons," she said. "It might be an concept that seems a bit incongruous to our misplaced ideas of a rather ruthless and aggressive past, but actually it ought to be expected that Neanderthals – and even Neanderthals and our human ancestors together – kissed."