Ancient Hominins and Early Humans Were Likely Kissing, Scientists Suggest

Among seabirds to Arctic mammals, primates to great apes, various animals appear to kiss. Currently, scientists propose that ancient hominins did it too – and might even have locked lips with modern humans.

Common Oral Evidence

This isn't the initial instance scientists have proposed ancient relatives and Homo sapiens were closely connected. Among previous studies, scientists have found humans and their thick-browed cousins possessed the same mouth microbe for hundreds of thousands of years after the evolutionary divergence, implying they exchanged oral fluids.

"Likely they were engaging in intimate contact," she said, explaining that the idea aligned with studies that has revealed humans of certain genetic backgrounds contain ancient genetic material in their genetic makeup, revealing genetic mixing was occurring.

Intimate Spin

"This offers a different spin on human-Neanderthal relations," the lead researcher commented.

Publishing in the journal a scientific periodical, Brindle and her team report how, to investigate the evolutionary origins of intimate contact, they first had to develop a description that was not restricted by how humans kiss.

Defining Kissing

"There have been some efforts to describe a kiss, but it's very much been human-centric, which implies 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.

Nonetheless, she said some behaviors that looked like kissing were distinct activities – such as the chewing and transfer of food, or "mouth contact", observed in fish called certain marine animals.

As a result the research group came up with a definition of kissing centered around friendly interactions involving intentional mouth-to-mouth contact with a member of the identical group, with some motion of the mouth but absence of nutrition.

Research Methods

The lead researcher said they focused on accounts of kissing in primates from the African continent and Asian regions, including bonobos, apes and great apes, and employed online videos to verify the reports.

Scientists then integrated this data with information on the evolutionary relationships between extant and extinct species of such primates.

Historical Origins

The team propose the results suggest intimate contact evolved approximately 21.5m and 16.9m years ago in the predecessors of the large apes.

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

"The fact that humans kiss, the fact that we currently have shown that ancient relatives very likely kissed, suggests that the two [species] are also likely to have engage," Brindle noted.

Evolutionary Significance

Although the scientific reasoning is discussed, the expert said kissing could be employed in sexual contexts to potentially enhance mating outcomes or assist in selecting between partners, while it might help reinforce bonding when practiced in a non-sexual manner.

Another expert in the activities of primates said that as kissing behavior was seen in a wide range of primates it made sense its roots extend far into our evolutionary past, and an analysis of different forms of intimate behavior among a wider variety of animals might extend its origins back even earlier still.

"Behaviors that we think of as characteristics of human life, like kissing, are not unique to us if we examine carefully at other animals," he said.

Cultural Aspects

Another professor explained that intimate contact had a cultural element as it was not universal to all societies.

"Nonetheless, as humans we succeed or struggle on the strength of our relationships, and ways of encouraging confidence and intimacy will have been important for millions of years," she said. "This could represent an image that appears a bit contradictory to our misplaced ideas of a rather ruthless and aggressive past, but actually it ought to be no surprise that Neanderthals – and including Neanderthals and our own species collectively – kissed."