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From seabirds to Arctic mammals, chimpanzees to great apes, various animals engage in mouth-to-mouth contact. Currently, researchers propose that Neanderthals did it too – and possibly locked lips with early Homo sapiens.

Shared Microbial Evidence

It is not the first time scientists have proposed Neanderthals and Homo sapiens were intimately acquainted. In earlier research, researchers have discovered humans and their thick-browed cousins shared the identical oral bacteria for millions of years after the two species split, suggesting they exchanged oral fluids.

"Likely they were kissing," the researcher noted, explaining that the idea aligned with research that has revealed humans of certain genetic backgrounds contain Neanderthal DNA in their genetic makeup, revealing genetic mixing was at play.

Romantic Interpretation

"This offers a more romantic perspective on ancient interactions," the lead researcher said.

Publishing in the journal a scientific periodical, Brindle and her team report how, to explore the historical roots of intimate contact, they first had to come up with a description that was not restricted by how people kiss.

Defining Kissing

"There have been some previous attempts to describe a intimate act, but it's largely focused on humans, which means that essentially non-human species don't kiss. Currently we know that they likely engage, it may appear different from what our intimate contact looks like," explained Brindle.

However, she said some actions that resembled kissing were something rather different – such as the processing and food sharing, or "mouth contact", seen in fish known as certain marine animals.

Consequently the team came up with a description of intimate contact centered around friendly interactions involving intentional mouth-to-mouth contact with a member of the identical group, with some movement of the oral area but absence of nutrition.

Research Methods

Brindle explained they focused on accounts of intimate behavior in non-human species from the African continent and Asia, including primates, chimpanzees and great apes, and used digital recordings to confirm the reports.

Scientists then integrated this information with information on the evolutionary relationships between extant and ancient types of such animals.

Historical Timeline

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

Placement of ancient hominins on this family tree means it is likely they, too, indulged in a kiss, the scientists conclude. But the behavior might not have been confined to their own species.

"Reality that modern people engage intimately, the fact that we currently have demonstrated that ancient relatives probably engaged, suggests that the both groups are also likely to have engage," the researcher noted.

Biological Importance

Although the evolutionary explanation is discussed, the expert explained kissing could be employed in sexual contexts to potentially increase reproductive success or assist in selecting between partners, while it could assist reinforce bonding when practiced in a platonic way.

A separate researcher in the activities of primates said that as kissing behavior was seen in a wide range of primates it made sense its roots lie deep in our ancient history, and an examination of different forms of intimate behavior among a wider variety of animals might push its beginnings back further still.

"Behaviors that we consider as signatures of our species, like intimate contact, are not exclusive to us if we look closely at other animals," the expert noted.

Social Aspects

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

"However, as humans we thrive or fail on the quality of our relationships, and methods of encouraging confidence and closeness will have been significant for eons," she said. "This could represent an concept that seems a bit contradictory to our incorrect assumptions of a supposedly aggressive and aggressive past, but really it ought to be no surprise that Neanderthals – and even Neanderthals and our human ancestors collectively – engaged intimately."