Ancient Smooches: Oxford Study Suggests Neanderthals and Early Humans Shared Kisses

A groundbreaking new study from the University of Oxford indicates that Neanderthals and early modern humans likely engaged in kissing, offering a fascinating glimpse into their intimate interactions. Published in the journal Evolution and Human Behavior on Tuesday, November 18, 2025, the research challenges previous assumptions about our ancient relatives.

This intriguing conclusion is drawn from an analysis of the evolutionary origins of kissing across primates and the discovery of shared mouth microbes between the two hominin species. The findings suggest that this affectionate behavior has roots stretching back millions of years, according to iflscience.

The research adds a "romantic spin" to our understanding of human-Neanderthal relations, particularly given the established evidence of interbreeding between the groups. This new perspective suggests a more complex and tender dynamic than often portrayed, as reported by The Guardian.

Dr. Matilda Brindle, an evolutionary biologist at the University of Oxford and lead author of the study, emphasized the systematic approach taken. She told 404 Media that it was "baffling" that the evolutionary perspective of kissing hadn't been explored in such depth before.

The study posits that the evolutionary "first kiss" among primates likely occurred at least 21 million years ago, long before the emergence of modern humans or Neanderthals. This deep evolutionary history supports the idea that Neanderthals would have also practiced kissing, Discover Magazine noted.

Previous research has already confirmed that humans of non-African ancestry carry Neanderthal DNA, indicating significant interbreeding events. The shared oral microbes further strengthen the hypothesis of close contact, including the exchange of saliva through kissing, according to the Smithsonian Institution's Human Origins Program.

• The Oxford study meticulously reconstructed the evolutionary timeline of kissing by analyzing observations of this behavior in modern primates and other animals. Researchers, including Dr. Brindle, gathered data on non-aggressive, mouth-to-mouth contact without food transfer across various primate species, such as bonobos, chimpanzees, and orangutans. This extensive analysis, repeated 10 million times using statistical modeling, traced the origin of kissing back to the common ancestor of large apes approximately 21 million years ago, iflscience reported.

• A key piece of evidence supporting the Neanderthal kissing hypothesis comes from the discovery of shared oral microbes, specifically *Methanobrevibacter oralis*, between Neanderthals and early modern humans. Previous research, as discussed in the Oxford University Research Archive, hypothesized that the transfer of this microbe, linked to gum disease, could have occurred through lip kissing over 100,000 years ago. This suggests a level of intimacy that facilitated saliva exchange between the species.

• The well-documented interbreeding between Neanderthals and early modern humans provides a crucial context for the kissing theory. Genomic analysis has revealed that 1-4% of the genome of present-day non-African populations is derived from Neanderthals, as detailed by the Smithsonian. This genetic exchange, occurring between 47,000 and 65,000 years ago, implies frequent and intimate interactions, making the act of kissing a plausible component of their relationships.

• To ensure a broad and accurate assessment, the research team developed a specific definition of kissing that extended beyond human-centric views. The Guardian explained that they defined it as "friendly interactions involving directed mouth-to-mouth contact with a member of the same species, with some movement of the mouth but no transfer of food." This allowed for the inclusion of similar behaviors observed in other primates, such as bonobos and chimpanzees.

• The adaptive benefits of kissing have long been an evolutionary puzzle, as it carries risks like disease transmission. However, Dr. Brindle suggested to 404 Media that the persistence of kissing implies significant benefits, such as mate evaluation (e.g., assessing breath) or reinforcing social bonds in both romantic and platonic contexts. IFLScience also noted that it might have evolved from grooming behaviors.

• While deeply rooted in our primate ancestry, kissing is not a universal human behavior, as noted by Discover Magazine. Co-author Catherine Talbot highlighted that it is only documented in 46 percent of human cultures, raising questions about the interplay between biological evolution and cultural invention. This cultural variability suggests that while the capacity for kissing is ancient, its expression and significance are shaped by societal norms.

• Dr. Matilda Brindle expressed her surprise at the limited existing data on kissing across animal species. She told 404 Media that she hopes this study will inspire other scientists to conduct more observations of kissing in wild and captive animal populations. Such future research could further illuminate the diverse forms and functions of this ancient behavior across the animal kingdom.

• The implications of this research extend to our understanding of Neanderthal social complexity. By suggesting that Neanderthals engaged in kissing, the study contributes to a growing body of evidence that portrays them not as crude, brutish figures, but as beings capable of complex social behaviors and emotional connections, similar to early modern humans. This reframes their interactions as potentially more affectionate and nuanced, as implied by The Guardian.