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

Among seabirds to polar bears, chimpanzees to orangutans, certain species appear to kiss. Currently, researchers propose that ancient hominins also engaged in this behavior – and possibly locked lips with modern humans.

Common Microbial Evidence

It is not the first time scientists have suggested ancient relatives and Homo sapiens were intimately acquainted. Among earlier research, researchers have found humans 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 engaging in intimate contact," she said, explaining that the idea chimed with research that has revealed humans of certain genetic backgrounds contain ancient genetic material in their genetic makeup, demonstrating genetic mixing was occurring.

Intimate Spin

"This offers a more romantic spin on human-Neanderthal relations," the lead researcher said.

Writing in the journal a scientific periodical, Brindle and her team report how, to explore the historical roots of intimate contact, they first had to develop a definition that was not limited to how humans smooch.

Describing Intimate Contact

"Previously there were some previous attempts to describe a intimate act, but it's largely focused on humans, which implies that essentially non-human species do not engage in this. Currently we understand that they probably do, it may appear different from what our intimate contact resembles," explained the evolutionary biologist.

However, she said some actions that resembled kissing were distinct activities – such as the processing and food sharing, or "kiss-fighting", observed in fish called certain marine animals.

Consequently the team developed a definition of intimate contact centered around social behaviors involving intentional oral interaction with a individual of the same species, with some motion of the oral area but no transfer of nutrition.

Study Methods

Brindle explained they focused on accounts of intimate behavior in primates from Africa and Asia, including primates, chimpanzees and great apes, 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 primates.

Historical Origins

The team propose the results suggest intimate contact developed somewhere between 21.5m and 16.9m years ago in the ancestors of the great primates.

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

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

Evolutionary Significance

Although the scientific reasoning is debated, Brindle explained intimate contact could be used in sexual contexts to potentially enhance reproductive success or assist in selecting between mates, while it might help reinforce bonding when used in a platonic way.

Another expert in the behavior of great apes 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 wider variety of animals might push its origins back even earlier still.

"Things that we consider as characteristics of human life, like kissing, are not unique to us if we look closely at different species," he said.

Social Aspects

Another professor explained that intimate contact had a social component as it was not universal to all human groups.

"However, as humans we succeed or struggle on the quality of our relationships, and methods of promoting confidence and closeness will have been important for millions of years," she said. "It might be an concept that appears a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but really it ought to be no surprise that Neanderthals – and even them and our human ancestors collectively – kissed."