🔗 Share this article

Among Galápagos albatrosses to polar bears, primates to orangutans, certain species engage in mouth-to-mouth contact. Currently, researchers propose that ancient hominins did it too – and possibly exchanged kisses with early Homo sapiens.

Shared Oral Clues

It is not the first time scientists have proposed ancient relatives and Homo sapiens were closely connected. Among previous studies, researchers have found humans and their Neanderthal relatives shared the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, implying they swapped saliva.

"Probably they were kissing," she said, adding that the concept chimed with studies that has revealed humans of non-African ancestry contain ancient genetic material in their genetic makeup, demonstrating interbreeding was at play.

Intimate Spin

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

Writing in the journal a scientific periodical, the researcher and colleagues report how, to explore the evolutionary origins of intimate contact, they first had to develop a description that was not limited to how people kiss.

Defining Kissing

"Previously there were some efforts to describe a intimate act, but it's largely human-centric, which means that basically 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," explained Brindle.

However, she noted some actions that looked like intimate contact were something rather different – such as the processing and transfer of food, or "mouth contact", observed in aquatic species known as French grunts.

As a result the team developed a definition of kissing based on friendly interactions involving intentional oral interaction with a member of the identical group, with some motion of the oral area but no transfer of nutrition.

Research Approach

Brindle said they concentrated on reports of kissing in non-human species from the African continent and Asian regions, including bonobos, apes and great apes, and used digital recordings to verify the reports.

The researchers then integrated this data with information on the evolutionary relationships between extant and ancient species of such primates.

Evolutionary Origins

The team propose the findings indicate intimate contact developed somewhere between 21.5 million and 16.9 million years ago in the predecessors of the large apes.

Placement of Neanderthals on this evolutionary lineage means it is likely they, too, indulged in a kiss, the scientists say. But the behavior may not have been confined to their own species.

"The fact that modern people kiss, the reality that we now have shown that ancient relatives very likely kissed, indicates that the two [species] are also likely to have engage," Brindle added.

Evolutionary Significance

Although the scientific reasoning is debated, the expert explained kissing could be employed in reproductive situations to possibly enhance reproductive success or assist in selecting between mates, while it could assist strengthen connections when used in a platonic way.

Another expert in the activities of primates said that as intimate contact was observed in a broad spectrum of apes it made sense its origins lie deep in our evolutionary past, and an examination of various types of kissing 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 unique to us if we examine carefully at other animals," he said.

Social Elements

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

"Nonetheless, as humans we thrive or fail on the quality of our emotional bonds, and ways of promoting confidence and closeness will have been significant for eons," she said. "It might be an concept that appears a bit contradictory to our misplaced ideas of a supposedly aggressive and aggressive past, but actually it ought to be no surprise that Neanderthals – and even Neanderthals and our human ancestors collectively – kissed."