By Toby Sterling
AMSTERDAM (Reuters) – Kissing began not with star-crossed human lovers, but with the primate ancestors of great apes around 20 million years ago, according to a study published on Wednesday.
Researchers from the University of Oxford and the Florida Institute of Technology wanted to determine when kissing began, given that from an evolutionary perspective it provides no obvious survival benefit and could spread disease.
Yet humans, chimpanzees, bonobos, orangutans and gorillas all kiss, strongly suggesting that the habit was inherited from a common ancestor. The study scientists combined observations of primate behavior with data on evolutionary relationships, to go back in time and try to date the first kiss.
“Using these two key pieces of information, we used a modeling approach that allowed us to simulate different evolutionary scenarios,” said lead author Dr Matilda Brindle from Oxford’s Department of Biology. Running the model millions of times places this first kiss between 21.5 and 16.9 million years ago.
The results were published in the journal Evolution and Human Behavior.
The scientists’ unromantic definition of kissing was “non-aggressive, mouth-to-mouth contact that did not involve the transfer of food.” This included sexual kisses as well as platonic kisses such as those between family members or during friendly greetings. How kissing originated remains a matter of debate, as does why it persisted.
“Some people suggest that sexual kissing is a useful way to assess the quality or suitability of a partner,” Brindle said. “Alternatively, kissing could be a kind of foreplay, increasing sexual arousal and increasing the chances of fertilization.”
Platonic pecks are thought to be used to manage complex social relationships or strengthen bonds, she said.
The study argues that Neanderthals and humans probably also locked lips, given evidence that they interbred and shared an oral microbe – a sign that they exchanged saliva – long after the two species diverged, 450,000 to 750,000 years ago.
(Reporting by Toby Sterling, Editing by Alexandra Hudson)
