Kissing might seem like a simple cultural practice, but it’s deeply rooted in our evolutionary history. Recent research from the University of Oxford reveals fascinating insights about its origins.
Scientists studied the behavior of primates, ancient oral microbes, and genetic connections among early human groups. They found that even our ancestors, like Neanderthals, likely engaged in mouth-to-mouth contact.
Why Kissing Intrigues Scientists
Despite the risks of spreading germs through saliva, kissing continues to be common in many cultures. This raises questions: Why has this behavior persisted? Dr. Matilda Brindle, a leading biologist in the study, aimed to understand if kissing is a cultural practice or a biological trait shared with other apes.
The team looked at how different animals use mouth contact for various purposes—such as bonding or aggression. They defined kissing as gentle, non-aggressive mouth contact without transferring food, capturing a clearer picture of its role across species.
They reviewed numerous videos and reports, finding that chimpanzees, bonobos, and many monkey species engage in similar mouth contact during social interactions.
How Kissing Evolved
The researchers used phylogenetic analysis to map out kissing behavior on evolutionary trees. They employed Bayesian modeling to simulate how kissing could have developed over millions of years across species. Their findings suggest that kiss-like behavior likely originated in a common ancestor of large apes about 21.5 to 16.9 million years ago.
Dr. Brindle pointed out that this study shines a light on the diverse intimate behaviors in primates, highlighting that what seems simple can have deep evolutionary connections.
Microbes and Historical Links
Further evidence of kissing among ancient humans comes from studies of the oral microbiome. By analyzing ancient dental plaque, researchers discovered links between Neanderthal and early human mouth bacteria, suggesting that intimate contact and shared food likely allowed these microbes to circulate between different groups.
Genetic studies indicate that interbreeding occurred between Neanderthals and early Homo sapiens. This suggests that close contact—possibly including kissing—was a part of their interactions.
Cultural Variations in Kissing
Today, kissing varies widely across cultures. A study involving 168 societies found that romantic kissing is more common in complex societies, while it’s often absent in smaller communities, where other forms of affection, like hugs or shared meals, might be preferred. As Catherine Talbot from the Florida Institute of Technology points out, only 46% of cultures document kissing.
Why Did Kissing Begin?
While researchers continue to explore its origins, several theories exist. Kissing might help reduce tension, allow people to assess a partner’s health through smell, or even enhance immunity by sharing microbes. Since behavioral traits don’t leave physical evidence, scientists rely on dental studies and genetic analysis combined with observations of modern primates.
As research continues, there’s potential to include more species and fossil data to paint a clearer picture of when and where kissing first appeared. For now, it remains a complex behavior linking modern humans to our ancient relatives.
The findings from this study can be found in the journal Evolution and Human Behavior. Understanding the deep roots of kissing offers a glimpse into how intimate behaviors connect us across time and species.
