Among seabirds to polar bears, primates to orangutans, certain species appear to kiss. Now, scientists suggest that ancient hominins also engaged in this behavior – and might even have locked lips with early Homo sapiens.
Shared Oral Evidence
It is not the first time scientists have proposed Neanderthals and early modern humans were closely connected. Among earlier research, scientists have discovered modern people and their Neanderthal relatives shared the identical oral bacteria for hundreds of thousands of years after the evolutionary divergence, suggesting they exchanged oral fluids.
"Probably they were engaging in intimate contact," the researcher noted, explaining that the idea chimed with research that has revealed people of certain genetic backgrounds have bits of Neanderthal DNA in their genetic makeup, revealing interbreeding was occurring.
Intimate Interpretation
"This offers a more romantic spin on ancient interactions," the lead researcher said.
Writing in the publication Evolution and Human Behavior, the researcher and her team detail how, to investigate the historical roots of kissing, they first had to come up with a description that was not limited to how people kiss.
Describing Kissing
"There have been some efforts to describe a intimate act, but it's largely focused on humans, which implies that basically non-human species do not engage in this. Now we understand that they probably do, it may appear different from what human kissing resembles," explained the evolutionary biologist.
However, she noted some actions that resembled intimate contact were distinct activities – such as the chewing and transfer of food, or "kiss-fighting", seen in aquatic species known as French grunts.
Consequently the research group developed a description of kissing based on friendly interactions involving directed mouth-to-mouth contact with a individual of the same species, with some movement of the mouth but absence of nutrition.
Study Approach
Brindle explained they focused on accounts of kissing in non-human species from Africa and Asia, including bonobos, apes and orangutans, and used digital recordings to confirm the observations.
Scientists then combined this data with information on the evolutionary relationships between extant and ancient types of such primates.
Historical Timeline
Researchers propose the findings indicate intimate contact developed approximately 21.5 million and 16.9m years ago in the predecessors of the great primates.
The position of Neanderthals on this evolutionary lineage suggests it is likely they, too, engaged in a intimate act, the scientists conclude. But the behavior may not have been confined to their specific group.
"The fact that modern people engage intimately, the reality that we now have demonstrated that ancient relatives very likely kissed, indicates that the two [species] are probably did kissed," the researcher added.
Biological Importance
While the scientific reasoning is discussed, the expert explained kissing could be employed in sexual contexts to possibly increase mating outcomes or help choose between partners, while it could assist reinforce bonding when used in a non-sexual manner.
A separate researcher in the behavior of primates commented that as intimate contact was observed in a wide range of primates it was logical its roots extend far into our ancient history, and an analysis of different forms of intimate behavior among a broader range of species might extend its beginnings back further still.
"Things that we consider as signatures of our species, like kissing, are not unique to us if we look closely at different species," he said.
Social Elements
Another professor explained that intimate contact had a cultural element as it was not common to all societies.
"Nonetheless, as humans we thrive or fail on the quality of our relationships, and ways of promoting trust and intimacy will have been significant for millions of years," she said. "This could represent an concept that appears a bit incongruous to our incorrect assumptions of a rather ruthless and aggressive past, but actually it should be no surprise that Neanderthals – and including Neanderthals and our human ancestors collectively – engaged intimately."
