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From Galápagos albatrosses to polar bears, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Now, researchers suggest that Neanderthals also engaged in this behavior – and might even have locked lips with modern humans.

Shared Oral Evidence

This isn't the initial instance experts have proposed Neanderthals and Homo sapiens were intimately acquainted. Among previous studies, researchers have discovered modern people and their thick-browed cousins possessed the identical oral bacteria for hundreds of thousands of years after the two species split, implying they exchanged oral fluids.

"Probably they were kissing," the researcher noted, adding that the concept aligned with studies that has revealed people of non-African ancestry contain Neanderthal DNA in their genetic makeup, demonstrating genetic mixing was occurring.

Intimate Spin

"This offers a different spin on human-Neanderthal relations," the lead researcher 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 Intimate Contact

"Previously there were some efforts to describe a intimate act, but it's largely human-centric, which implies that essentially non-human species do not engage in this. Currently we understand that they probably do, it might just not look from what our intimate contact resembles," said Brindle.

Nonetheless, she noted some actions that looked like kissing were distinct activities – such as the chewing and food sharing, or "mouth contact", seen in aquatic species called French grunts.

Consequently the team developed a description of kissing centered around social behaviors involving directed oral interaction with a individual of the identical group, with some movement of the mouth but absence of nutrition.

Study Methods

The lead researcher said they concentrated on accounts of kissing in primates from the African continent and Asian regions, including primates, chimpanzees and orangutans, and employed online videos to confirm the observations.

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

Evolutionary Origins

The team propose the findings suggest 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 probable they, too, indulged in a kiss, the scientists conclude. But the activity might not have been limited to their specific group.

"The fact that modern people engage intimately, the reality that we now have shown that ancient relatives very likely kissed, suggests that the both groups are also likely to have engage," Brindle added.

Evolutionary Significance

Although the scientific reasoning is debated, Brindle explained kissing could be used in sexual contexts to potentially enhance mating outcomes or assist in selecting between partners, while it could assist reinforce bonding when used in a non-sexual manner.

A separate researcher in the activities of primates said that as intimate contact was seen in a wide range of primates it made sense its origins extend far into our ancient history, and an examination of different forms of kissing among a wider variety of animals might extend its origins back further still.

"Things that we consider as characteristics of human life, like kissing, are not exclusive to us if we examine carefully at other animals," the expert noted.

Cultural Aspects

Another professor explained that intimate contact had a cultural element as it was not common to all human groups.

"However, as people we thrive or fail on the quality of our relationships, and methods of encouraging trust and closeness will have been significant for eons," the professor stated. "It might be an concept that seems a bit contradictory to our incorrect assumptions of a supposedly aggressive and aggressive past, but really it should be expected that ancient hominins – and including Neanderthals and our own species collectively – engaged intimately."