New Study Reveals Kissing’s Origins in Human Ancestors

Research from the University of Oxford has uncovered evidence suggesting that kissing originated in the common ancestor of humans and large apes approximately 21 million years ago. The study, published in the journal Evolution and Human Behavior, also indicates that Neanderthals likely participated in this behavior, expanding our understanding of social interactions in early human relatives.

Kissing presents an intriguing evolutionary question. While it holds cultural and emotional significance across numerous human societies, it carries risks, such as disease transmission, without providing a clear reproductive or survival advantage. Despite its prevalence in human interactions, the evolutionary history of kissing has received limited attention from researchers until now.

Uncovering the Evolutionary History of Kissing

The study marks the first comprehensive attempt to analyze kissing through a cross-species lens, utilizing the primate family tree. Researchers defined kissing as non-aggressive, mouth-to-mouth contact that does not involve food transfer. This definition allowed for the examination of kissing behaviors across different species, including chimpanzees, bonobos, and orangutans, which have all been observed engaging in kissing.

Following this, the research team conducted a phylogenetic analysis, treating kissing as a trait mapped onto the primate family tree. They employed a statistical method known as Bayesian modeling, simulating various evolutionary scenarios along the branches of the tree to estimate the likelihood that different ancestors engaged in kissing. This model was executed 10 million times to ensure robust statistical findings.

Dr. Matilda Brindle, the lead author and an evolutionary biologist at Oxford’s Department of Biology, remarked, “This is the first time anyone has taken a broad evolutionary lens to examine kissing. Our findings add to a growing body of work highlighting the remarkable diversity of sexual behaviors exhibited by our primate cousins.”

Implications for Future Research and Cultural Understanding

While the researchers acknowledge that current data is limited, particularly outside the large ape family, the study establishes a framework for future investigations. This framework allows primatologists to document kissing behaviors in nonhuman animals with a consistent definition. Co-author Catherine Talbot, Assistant Professor in the College of Psychology at the Florida Institute of Technology, noted that kissing is documented in only 46% of human cultures, indicating significant variability in social norms and contexts surrounding this behavior.

Talbot raised important questions about whether kissing is an evolved behavior or a cultural invention. “This is the first step in addressing that question,” she said.

The findings from the University of Oxford not only expand our understanding of the origins of kissing but also highlight the complex social behaviors shared among primates, offering a new perspective on the evolution of human interactions. Researchers hope that this work will pave the way for more comprehensive studies into the social behaviors of both modern and extinct species, enriching our understanding of human evolution.