Ancient Hominins and Early Humans Were Likely Kissing, Researchers Propose

Among seabirds to polar bears, chimpanzees to orangutans, various animals appear to kiss. Currently, scientists propose that ancient hominins did it too – and might even have exchanged kisses with early Homo sapiens.

Common Microbial Evidence

It is not the first time scientists have suggested ancient relatives and early modern humans were closely connected. Among earlier research, scientists have found humans and their thick-browed cousins shared the identical oral bacteria for hundreds of thousands of years after the two species split, suggesting they swapped saliva.

"Likely they were kissing," she said, adding that the concept chimed with studies that has revealed people of certain genetic backgrounds have bits of ancient genetic material in their genome, revealing genetic mixing was occurring.

Intimate Interpretation

"It certainly puts a more romantic perspective on ancient interactions," Brindle said.

Writing in the publication a scientific periodical, the researcher and colleagues report how, to investigate the evolutionary origins of intimate contact, they first had to come up with a description that was not limited to how people kiss.

Defining Kissing

"There have been some previous attempts to describe a kiss, but it's largely focused on humans, which means that basically non-human species don't kiss. Now we know that they probably do, it might just not look from what human kissing resembles," explained Brindle.

Nonetheless, she noted some behaviors that looked like intimate contact were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", seen in fish known as certain marine animals.

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

Study Approach

Brindle explained they focused on reports of intimate behavior in non-human species from the African continent and Asian regions, including bonobos, chimpanzees and great apes, and employed online videos to confirm the reports.

Scientists then combined this information with details on the evolutionary relationships between extant and extinct types of such primates.

Evolutionary Origins

Researchers propose the findings indicate intimate contact developed approximately 21.5 million and 16.9 million years ago in the predecessors of the large apes.

The position of Neanderthals on this family tree suggests it is likely they, too, indulged in a kiss, the researchers conclude. But the behavior may not have been limited to their own species.

"The fact that humans engage intimately, the fact that we currently have demonstrated that Neanderthals probably kissed, indicates that the both groups are probably did engage," Brindle added.

Biological Importance

While the scientific reasoning is debated, the expert said intimate contact could be employed in reproductive situations to potentially increase reproductive success or assist in selecting between mates, while it might help reinforce bonding when practiced in a platonic way.

A separate researcher in the behavior of primates said that as kissing behavior was seen in a wide range of primates it made sense its roots extend far into our ancient history, and an examination of various types of kissing among a broader range of species might extend its beginnings back even earlier still.

"Things that we consider 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 cultural element as it was not common to all human groups.

"Nonetheless, as humans we succeed or struggle on the strength of our relationships, and methods of encouraging trust and closeness will have been significant for millions of years," she said. "This could represent an concept that seems a bit incongruous to our incorrect assumptions of a supposedly aggressive and aggressive past, but actually it should be no surprise that Neanderthals – and even them and our human ancestors together – engaged intimately."