New research suggests that the act of kissing may have begun long before modern humans existed.
Kissing originated about 21 million years ago, from the common ancestor of humans and other great apes, according to a study published Wednesday (Nov. 19) in the journal. Evolution and human behavior. Meanwhile, wise man probably appeared about 300,000 years ago.
“This is the first time anyone has looked at kissing from a broad evolutionary perspective,” said the study's lead author. Matilda Brindlethe evolutionary biologist from Oxford University said in a statement. “Our findings add to a growing body of work highlighting the remarkable diversity of sexual behavior exhibited by our primate cousins.”
Model kissing
Before dating the world's oldest kisses, an international team of researchers has determined what it means to kiss. This was important because other mouth-to-mouth actions in nature are similar to kissing. For example, mothers of orangutans and chimpanzees pass chewed food to their babies mouth to mouth, and the fish engage in “kissing” to assert dominance or compete for territory. The researchers ultimately defined kissing as “non-aggressive mouth-to-mouth contact that does not involve the transfer of food,” they wrote in a statement.
Based on this definition, various modern primates – including bonobos, gorillas, chimpanzees, orangutans, macaques and baboons – were spotted kissing.
The researchers then used a statistical technique called Bayesian modeling to reconstruct the evolutionary history of kissing. They looked at kissing as a biological trait and tested many possible pathways for the behavior to see how likely it was that different ancestors also kissed. They ran the model 10 million times to ensure the validity and reliability of the results.
They concluded that kissing evolved once in the common ancestor of great apes (Hominids) sometime between 21.5 and 16.9 million years ago.
However, kissing was absent in the ancestors of Macacina and Papionina (groups that include macaques and baboons), suggesting that kissing evolved separately in modern species belonging to these groups. The team determined this by extrapolating the past behavior of modern species to that of their common ancestors.
Although more evidence is needed, researchers say kissing may have evolved from the practice of pre-chewing and passing food from mother to infant. This practical behavior of eating together may have been repurposed into what we now call kissing.
How does this fit with earlier research on kissing?
The discovery that Neanderthals kissed not only each other, but also modern humans is not news to anthropologists.
“I'm not sure the current study adds anything substantially new to our knowledge of this behavior in Neanderthals,” April Nowella Paleolithic archaeologist and professor of anthropology at the University of Victoria in British Columbia, who was not involved in the study, told Live Science by email.
But the new study is consistent with previous findings. Nowell noted that “intriguing evidence” emerged in 2017when another research team compared microbes preserved in the dental plaque of a Neanderthal who lived 48,000 years ago with microbes found in the mouths of modern humans. The team concluded that Neanderthals and X. sapiens It's possible they were kissing each other, although the microbial overlap could also reflect sharing food or water, said Nowell, who was not involved in the study.
Moreover, we already know that X. sapiens and Neanderthals mated for about 7000 year pulseso it is possible that some kissing took place then, assuming that some ancient mating patterns were similar to those of today.
However, it is unclear how widespread kissing was among our human relatives. Because kissing is not a universal behavior among modern people. only about half of cultures do this “Nowell said the same variability may have existed in the past.” If Neanderthals kissed, she said, “it might be a behavior that some Neanderthal communities did and others did not.”
Scientists are still not sure why kissing persists in so many species, especially given the potential downsides such as spreading disease. One idea is that kissing helps people increase reproductive success. For example, kissing a potential partner can help people judge the quality of a partner through subtle chemical cues that can provide insight into a person's overall health, genetic compatibility, immune system and the composition of their oral microbiome, researchers write in a new study. Researchers have also suggested that kissing strengthens social bonds and may even benefit the immune system allowing the exchange of microbes.
