Ancient Hominins and Early Humans May Have Engaging in Intimate Contact, Researchers Suggest

From seabirds to polar bears, primates to orangutans, certain species appear to kiss. Currently, scientists propose that Neanderthals also engaged in this behavior – and possibly exchanged kisses with early Homo sapiens.

Shared Oral Clues

This isn't the initial instance scientists have proposed ancient relatives and early modern humans were intimately acquainted. Among previous studies, scientists have discovered modern people and their thick-browed cousins possessed the same mouth microbe for millions of years after the evolutionary divergence, suggesting they swapped saliva.

"Probably they were kissing," the researcher noted, explaining that the idea aligned with studies that has found people of non-African ancestry have bits of ancient genetic material in their genome, revealing interbreeding was at play.

Intimate Spin

"It certainly puts a different spin on human-Neanderthal relations," the lead researcher said.

Publishing in the publication a scientific periodical, Brindle and her team report how, to investigate the evolutionary origins of kissing, they first had to develop a definition that was not limited to how people kiss.

Defining Intimate Contact

"There have been some efforts to describe a intimate act, but it's largely human-centric, which means that basically other animals don't kiss. Currently we know that they likely engage, it might just not look from what human kissing looks like," explained the evolutionary biologist.

However, she noted some actions that resembled kissing were something rather different – such as the processing and transfer of food, or "mouth contact", observed in aquatic species known as certain marine animals.

Consequently the research group came up with a definition of intimate contact based on social behaviors involving intentional oral interaction with a individual of the identical group, with some movement of the oral area but absence of nutrition.

Study Methods

The lead researcher explained they focused on accounts of intimate behavior in non-human species from the African continent and Asia, including bonobos, apes and great apes, and used digital recordings to verify the reports.

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

Evolutionary Origins

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

Placement of Neanderthals on this family tree suggests it is likely they, too, indulged in a intimate act, the researchers conclude. But the activity may not have been confined to their own species.

"Reality that modern people kiss, the reality that we currently have shown that Neanderthals very likely kissed, indicates that the both groups are probably did kissed," Brindle noted.

Biological Importance

While the scientific reasoning is debated, Brindle said kissing could be used in sexual contexts to possibly enhance reproductive success or help choose between mates, while it could assist reinforce bonding when practiced in a non-sexual manner.

Another expert in the behavior of primates said that as kissing behavior was seen in a wide range of primates it was logical its roots extend far into our ancient history, 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 think of as signatures of human life, like kissing, are not exclusive to us if we look closely at different species," he said.

Social Elements

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

"Nonetheless, as humans we thrive or fail on the strength of our relationships, and ways of promoting confidence and closeness will have been important for eons," the professor stated. "This could represent an concept that appears a bit contradictory 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 own species together – engaged intimately."