Ancient Hominins and Early Humans Were Likely Engaging in Intimate Contact, Researchers Suggest

Among seabirds to polar bears, primates to great apes, various animals engage in mouth-to-mouth contact. Now, scientists propose that ancient hominins did it too – and might even have locked lips with modern humans.

Common Oral Clues

This isn't the initial instance experts have suggested Neanderthals and Homo sapiens were intimately acquainted. In earlier research, researchers have discovered modern people and their Neanderthal relatives possessed the identical oral bacteria for millions of years after the evolutionary divergence, implying they swapped saliva.

"Probably they were kissing," she said, explaining that the concept chimed with research that has found humans of non-African ancestry have bits of ancient genetic material in their genetic makeup, demonstrating interbreeding was at play.

Intimate Spin

"It certainly puts a different perspective on ancient interactions," Brindle said.

Publishing in the journal a scientific periodical, Brindle and her team report how, to explore the evolutionary origins of intimate contact, they first had to develop a definition that was not limited to how humans smooch.

Describing Intimate Contact

"Previously there were some previous attempts to define a kiss, but it's largely human-centric, 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 resembles," said the evolutionary biologist.

Nonetheless, she said some actions that resembled intimate contact were distinct activities – such as the chewing and transfer of food, or "mouth contact", observed in aquatic species known as French grunts.

Consequently the team came up with a definition of kissing centered around social behaviors involving directed mouth-to-mouth contact with a individual of the identical group, with some motion of the mouth but no transfer of food.

Study Approach

Brindle explained they concentrated on accounts of intimate behavior in primates from the African continent and Asia, including bonobos, apes and great apes, and used online videos to verify the observations.

The researchers then integrated this data with information on the genetic connections between extant and extinct types of such animals.

Historical Origins

The team propose the results suggest intimate contact developed approximately 21.5 million and 16.9 million years ago in the ancestors of the large apes.

Placement of Neanderthals on this evolutionary lineage suggests it is likely they, too, engaged in a kiss, the researchers conclude. But the activity might not have been limited to their specific group.

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

Biological Importance

Although the scientific reasoning is discussed, Brindle explained kissing could be employed in sexual contexts to potentially increase mating outcomes or help choose between mates, while it might help reinforce bonding when used in a platonic way.

Another expert in the activities of great apes said that as kissing behavior was seen in a wide range of primates it was logical its origins extend far into our evolutionary past, and an examination of various types of kissing among a wider variety of species might extend its origins back further still.

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

Social Elements

An archaeology expert said that intimate contact had a cultural element as it was not common to all societies.

"Nonetheless, as humans we succeed or struggle on the quality of our emotional bonds, and ways of promoting confidence and closeness will have been important for millions of years," the professor stated. "This could represent an image that appears a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but really it should be no surprise that ancient hominins – and even them and our human ancestors collectively – engaged intimately."