While kissing may feel like one of the most natural things in the world, this familiar behavior is quite mysterious – despite the lack of practical benefits and the real risk of disease transmission, various animals also kiss.
To shed light on the mystery of kissing, researchers have attempted to reconstruct the evolutionary history of kissing in the primate family tree, which includes mammals such as monkeys, apes, and humans. The team’s findings show that kissing is an ancient trait that evolved in the ancestors of great apes (such as humans) between 21.5 and 16.9 million years ago and persists in most living great ape species today.
“This is the first time that anyone has taken a broad evolutionary lens to examine kissing,” Matilda Brindle, an evolutionary biologist at the University of Oxford, said in a statement from the university. “Our findings add to a growing body of work highlighting the remarkable diversity of sexual behaviors displayed by our primate cousins.” Brindle is the lead author of a study published today in the journal Evolution and Human Behavior.
What is kiss?
First, the team had to scientifically define what a kiss is. This is harder than it sounds, given that many mouth-to-mouth behaviors can look like kissing and the definition should be consistent across different species. finally he made a decision unbelievably Romantic description: Non-aggressive mouth-to-mouth contact without the transfer of food. pucker up.
Brindle and colleagues then collected previously documented information about kissing across modern primate species, focusing on monkeys and apes that evolved in Europe, Africa and Asia, including chimpanzees, bonobos and orangutans (all three of which have been recorded kissing). Treating kissing as an evolutionary “trait”, the team ran a computer model 10 million times to simulate different primate evolutionary scenarios and estimate the probabilities of different ancestors kissing.
“By integrating evolutionary biology with behavioral data, we are able to draw informed conclusions about traits that do not fossilize – like kissing. This allows us to study social behavior in both modern and extinct species,” said study co-author Stuart West, an evolutionary biologist at the University of Oxford.
kissing partner
This method showed that Neanderthals also probably kissed. In addition to previous evidence showing that humans and our now extinct cousins transferred saliva and interbred with each other, the results strongly indicate that homo sapiens And Neanderthals also smooched each other.
“Although kissing may seem like a common or universal behavior, it is documented in only 46% of human cultures,” said Katherine Talbot, co-author of the study and an assistant professor in the School of Psychology at the Florida Institute of Technology. “Social norms and contexts vary widely across societies, raising the question of whether kissing is an evolved behavior or a cultural invention. This is a first step toward addressing that question.”
Naturally, given the methodology used, there are some important limitations to point out. The paper is based on previously recorded behaviors and computer simulations, not direct observations. This is particularly uncertain when it comes to extinct species, including Neanderthals. Furthermore, data beyond the great apes is sparse, limiting how far the findings can be extrapolated. The results also depend on the assumptions built into the model, meaning that the results may vary with different parameters.
At the very least, and as noted in the press release, the study provides a framework for future work and gives primatologists a way to record kissing behavior in non-human animals, using a consistent – if not complete buzzkill – definition.