After all, rather than being a recent cultural development, kissing on the mouth may have been practiced by other early humans.
There is widespread debate about when humans began kissing romantically.
Ancient texts suggest that sexual kissing was practiced in ancient Mesopotamia and Egypt at least 4,500 years ago, but as such kissing has only been documented in about 46% of human cultures, some argue that it is a cultural phenomenon that emerged relatively recently in human history.
However, there is evidence that Neanderthals exchanged oral bacteria with Homo sapiens, and chimpanzees, bonobos and orangutans have all been observed kissing. Therefore, it is possible that the behavior goes back much further than historical texts reveal.
It was in order to look for answers that a new study, in Evolution and Human Behaviorthey tried to determine the evolutionary history of kissing.
“Kissing seems a bit like an evolutionary paradox. It probably doesn’t help survival and could even be risky in terms of facilitating the transmission of pathogens”, noted the research leader, Matilda Brindlefrom the University of Oxford, cited by .
To estimate the likelihood that various ancestral species also practiced kissing, the team mapped this information onto a primate family tree and ran a statistical approach called Bayesian modeling 10 million times to simulate different evolutionary scenarios.
It turns out that Kissing probably evolved in ancient apes between close to 21.5 million and 16.9 million years ago.
Furthermore, there are 84% probability that our extinct human relatives, the Neanderthals also practiced kissing.
Still, the team was unable to collect enough data to say how the kiss evolved afterwards. But he suggested two hypotheses.
“In terms of sexual kissing, may increase reproductive success by allowing animals to evaluate mate quality. If someone has bad breath, then you can choose not to breed with them,” Brindle said.
Sexual kissing can also help with post-copulation success by promoting arousal, which can accelerate ejaculation and change vaginal pH to make it more hospitable to sperm.
The other main idea is that non-sexual kissing developed from social treatment and is useful for strengthening bonds and mitigating social tensions.
“Chimpanzees literally kiss and make up after a fight,” Brindle explained.
