🔗 Share this article

From seabirds to Arctic mammals, chimpanzees to orangutans, various animals appear to kiss. Now, scientists suggest that ancient hominins did it too – and might even have exchanged kisses with early Homo sapiens.

Common Oral Evidence

It is not the first time scientists have suggested ancient relatives and Homo sapiens were closely connected. Among earlier research, scientists have discovered modern people and their thick-browed cousins shared the identical oral bacteria for millions of years after the evolutionary divergence, suggesting they exchanged oral fluids.

"Likely they were kissing," the researcher noted, adding that the idea chimed with research that has found people of non-African ancestry contain ancient genetic material in their genetic makeup, demonstrating genetic mixing was occurring.

Romantic Interpretation

"This offers a different perspective on ancient interactions," Brindle said.

Publishing in the journal Evolution and Human Behavior, the researcher and colleagues detail how, to investigate the historical roots of intimate contact, they first had to develop a description that was not limited to how people smooch.

Defining Kissing

"Previously there were some previous attempts to describe a intimate act, but it's largely human-centric, which means that essentially non-human species do not engage in this. Currently we know that they probably do, it may appear different from what human kissing looks like," said Brindle.

Nonetheless, she said some behaviors that looked like kissing were something rather different – such as the chewing and food sharing, or "kiss-fighting", observed in aquatic species called certain marine animals.

Consequently the team came up with a description of kissing based on social behaviors involving intentional oral interaction with a individual of the same species, with some motion of the mouth but no transfer of food.

Research Methods

Brindle said they concentrated on accounts of kissing in primates from the African continent and Asia, including primates, chimpanzees and great apes, and employed digital recordings to confirm the observations.

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

Evolutionary Origins

Researchers propose the results suggest intimate contact developed somewhere between 21.5 million and 16.9 million years ago in the ancestors of the large apes.

The position of ancient hominins on this family tree means it is likely they, too, engaged in a intimate act, the scientists conclude. But the activity might not have been limited to their specific group.

"The fact that humans engage intimately, the reality that we currently have demonstrated that ancient relatives probably engaged, suggests that the two [species] are also likely to have kissed," the researcher added.

Biological Importance

Although the evolutionary explanation is discussed, Brindle explained intimate contact could be used in reproductive situations to possibly enhance mating outcomes or help choose between partners, while it could assist reinforce bonding when practiced in a non-sexual manner.

A separate researcher in the behavior of primates commented that as kissing behavior was seen in a broad spectrum of primates it was logical its origins lie deep in our ancient history, and an analysis of various types of kissing among a wider variety of species might extend 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 examine carefully at different species," he said.

Social Elements

An archaeology expert said that intimate contact had a cultural element as it was not common to all societies.

"Nonetheless, as people we succeed or struggle on the quality of our relationships, and ways of promoting trust and closeness will have been important for eons," the professor stated. "This could represent an image that seems a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but actually it should be no surprise that Neanderthals – and including Neanderthals and our own species together – engaged intimately."