Ancient Hominins and Early Humans May Have Kissing, Researchers Suggest

Among seabirds to Arctic mammals, primates to orangutans, certain species engage in mouth-to-mouth contact. Now, scientists suggest that Neanderthals did it too – and possibly locked lips with modern humans.

Common Oral Clues

It is not the first time experts have proposed Neanderthals and Homo sapiens were closely connected. In earlier research, scientists have discovered modern people and their thick-browed cousins shared the identical oral bacteria for millions of years after the two species split, implying they swapped saliva.

"Likely they were engaging in intimate contact," the researcher noted, adding that the concept chimed with studies that has revealed people of non-African ancestry contain ancient genetic material in their genetic makeup, revealing interbreeding was at play.

Romantic Interpretation

"This offers a different perspective on ancient interactions," Brindle said.

Writing in the journal Evolution and Human Behavior, Brindle and her team report how, to investigate the evolutionary origins of intimate contact, they first had to develop a description that was not limited to how humans kiss.

Describing Intimate Contact

"There have been some previous attempts to define a kiss, but it's very much been focused on humans, which implies that basically other animals do not engage in this. Now we know that they likely engage, it may appear different from what our intimate contact looks like," said Brindle.

Nonetheless, she said some behaviors that resembled kissing were distinct activities – such as the chewing and food sharing, or "mouth contact", seen in aquatic species known as certain marine animals.

Consequently the research group came up with a definition of kissing based on social behaviors involving directed oral interaction with a member of the identical group, with some motion of the oral area but absence of nutrition.

Research Approach

Brindle said they focused on accounts of kissing in primates from the African continent and Asian regions, including bonobos, chimpanzees and great apes, and employed online videos to verify the observations.

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

Evolutionary Timeline

The team say the results suggest kissing evolved approximately 21.5 million and 16.9m years ago in the ancestors of the great primates.

Placement of Neanderthals on this family tree means it is probable they, too, engaged in a kiss, the researchers say. But the activity may not have been confined to their own species.

"The fact that modern people engage intimately, the fact that we currently have shown that ancient relatives probably kissed, indicates that the both groups are probably did kissed," the researcher added.

Biological Significance

Although the evolutionary explanation is debated, Brindle said kissing could be used in sexual contexts to potentially enhance mating outcomes or help choose between partners, while it might help reinforce bonding when practiced in a platonic way.

Another expert in the behavior of great apes commented that as kissing behavior was observed in a wide range of primates it made sense its roots lie deep in our ancient history, and an examination of various types of kissing among a wider variety of animals might push its beginnings back even earlier still.

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

Cultural Aspects

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

"Nonetheless, as humans we thrive or fail on the quality of our relationships, and methods of promoting trust and intimacy will have been significant for millions of years," the professor stated. "This could represent an concept that appears a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but really it should be no surprise that Neanderthals – and including them and our human ancestors together – engaged intimately."