Daily Voice
By Chris Spiker From Daily Voice
In the words of Dua Lipa, one kiss is all it took about 21 million years ago.
That's roughly when scientists estimate that kissing first emerged in the common ancestor of humans and other great apes. British researchers published their findings in the journal Evolution and Human Behaviour on Wednesday, Nov. 19.
The study examined mouth-to-mouth kisses broadly across primates and other animals. Kissing was defined as nonaggressive interactions with "directed, intraspecific, oral-oral contact with some movement of the lips/mouthparts and no food transfer."
Dr. Matilda Brindle, the lead researcher and an evolutionary biologist at the University of Oxford, said the most recent common ancestor for humans, chimpanzees, and other primates likely kissed.
"It's important for us to understand that this is something we share with our non-human relatives," Dr. Brindle told the BBC. "We should be studying this behavior, not just dismissing it as silly because it has romantic connotations in humans."
Two prairie dogs kissing.
The researchers studied mouth-to-mouth contact in Afro-Eurasian monkeys and apes, as well as animals like wolves, prairie dogs, polar bears and Galápagos albatrosses. The scientists then built out evolutionary family trees to see when that kind of kissing most likely first appeared.
According to the study, kissing seems to have first evolved in the ancestor of the large apes after they split from the small apes, between 21.5 and 16.9 million years ago. Most living great apes kiss each other, including humans, chimpanzees, bonobos and orangutans.
A Barbary macaque kissing another macaque on the head.
Neanderthals also showed signs of kissing. One previous study found that modern humans and Neanderthals shared a type of bacteria found in saliva.
The researchers say that Neanderthals and early humans likely kissed, along with potentially interbreeding.
"That means that they must have been swapping saliva for hundreds of thousands of years after the two species split," Dr. Brindle said.
The study also looked at the evolutionary purpose behind kissing, since it doesn't help animals catch food or escape predators. Mouth-to-mouth contact can also spread illnesses, whether it's a common cold between humans or something far more deadly between animals.
One idea is that sexual kissing can help potential mates judge each other's health or compatibility through taste and smell, according to the researchers. Romantic or platonic kisses may also show trust, reduce conflict, build social bonds, or even provide immune system benefits.
Two polar bears with their mouths open next to each other.
The authors emphasized that kissing isn't even universal among humans, let alone when a romantic smooch is compared to animals nuzzling.
"For instance, while kissing is commonplace in many human societies, it does not seem to occur at all in others," they wrote in their conclusion. "It is important to establish whether this is also the case in nonhuman animals: is kissing widespread, or does it only occur in certain populations? If it is patchily distributed, this could indicate that kissing is a socially learnt, cultural phenomenon."
The researchers also noted that most kisses between primates occurs in captivity, with bonobos as an example of one species not yet observed kissing in the wild.
WTOP