🔗 Share this article

From Galápagos albatrosses to Arctic mammals, primates to great apes, various animals appear to kiss. Currently, researchers propose that ancient hominins did it too – and might even have locked lips with early Homo sapiens.

Common Oral Clues

This isn't the initial instance experts have proposed ancient relatives and Homo sapiens were intimately acquainted. Among earlier research, researchers have found modern people and their Neanderthal relatives shared the same mouth microbe for millions of years after the two species split, suggesting they swapped saliva.

"Probably they were kissing," the researcher noted, explaining that the concept aligned with studies that has found people of non-African ancestry have bits of ancient genetic material in their genome, demonstrating interbreeding was at play.

Romantic Interpretation

"This offers a different perspective on human-Neanderthal relations," Brindle commented.

Writing in the publication a scientific periodical, the researcher and colleagues report how, to explore the historical roots of kissing, they first had to develop a description that was not restricted by how people kiss.

Defining Kissing

"There have been some efforts to define a kiss, but it's very much been human-centric, which means that essentially other animals do not engage in this. Now we know that they probably do, it may appear different from what our intimate contact looks like," explained the evolutionary biologist.

Nonetheless, she noted some actions that resembled intimate contact were something rather different – such as the processing and transfer of food, or "kiss-fighting", observed in aquatic species called French grunts.

As a result the team developed a definition of intimate contact centered around social behaviors involving intentional mouth-to-mouth contact with a member of the identical group, with some motion of the mouth but absence of nutrition.

Study Methods

The lead researcher explained they focused on reports of kissing in non-human species from the African continent and Asia, including primates, apes and great apes, and used digital recordings to verify the reports.

The researchers then combined this data with details on the evolutionary relationships between extant and extinct types of such animals.

Historical Timeline

Researchers propose the results indicate intimate contact developed approximately 21.5 million and 16.9 million years ago in the predecessors of the great primates.

The position of Neanderthals on this family tree means it is probable they, too, indulged in a intimate act, the researchers say. But the activity may not have been confined to their specific group.

"Reality that modern people kiss, the reality that we currently have shown that ancient relatives probably engaged, suggests that the both groups are also likely to have kissed," the researcher noted.

Evolutionary Importance

While the scientific reasoning is debated, Brindle said kissing could be employed in sexual contexts to potentially increase reproductive success or help choose between mates, while it might help strengthen connections when practiced in a non-sexual manner.

Another expert in the behavior of great apes said that as intimate contact was seen in a wide range of apes it made sense its origins extend far into our ancient history, and an examination of various types of intimate behavior among a broader range of animals might extend its beginnings back even earlier still.

"Things that we think of as signatures of our species, like kissing, are not unique to us if we look closely at other animals," the expert noted.

Social Elements

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

"Nonetheless, as people we succeed or struggle on the quality of our relationships, and ways of promoting trust and intimacy will have been important for eons," the professor stated. "It might be an image that appears a bit incongruous to our misplaced ideas of a supposedly aggressive and aggressive past, but actually it should be no surprise that ancient hominins – and even them and our own species together – kissed."