
Researchers have developed a straightforward mathematical computer model to explore how human societies form and evolve over time. The study sheds light on the origins of one of humanity’s earliest social systems and offers insights into the forces that shape cultural behaviors.
Clans, groups of people who believe they share common ancestors, are often organized through rules about marriage. In many cases, members are encouraged to marry outside their clan, a practice that helps build connections between groups. These structures, known as kinship systems, have been observed across cultures and are considered one of the oldest forms of social organization.
A physicist’s perspective on human behavior
Kenji Itao, a researcher at the RIKEN Center for Brain Science in Japan, has long been fascinated by the patterns of human behavior. His curiosity led him to use tools from statistical physics—an area of science that simplifies complex phenomena through basic mathematics—to study human social systems.
“I wanted to explore how complex human kinship structures observed across diverse regions by cultural anthropologists are organized,” says Itao. “In particular, I desired to see whether such structures can emerge spontaneously within a simple model that assumes only competition over mates and ties between in-laws.”
To investigate, Itao collaborated with Kunihiko Kaneko, a researcher at the University of Tokyo. Together, they developed a mathematical model designed to mimic the formation and evolution of human kinship systems. The model focuses on two primary factors: population size and the extent to which traits differ between parents and their children.
Their findings, published in the Proceedings of the National Academy of Sciences, revealed that specific social structures emerge under certain conditions. For example, the model predicted patterns of kinship organization that align with those documented by cultural anthropologists in real societies. This success highlights the potential of simple mathematical tools to explain seemingly complex human interactions.
“For me, the most surprising thing is that a simple mathematical model based on anthropological observations can explain some of the mechanisms for the evolution of complex human kinships,” Itao said.
Two factors drive the development of social structures
The researchers identified two key factors that drive the development of social structures. One is the size of the population, which determines the pool of potential relationships. The other is a “cultural mutation rate,” which reflects how traits or behaviors shift across generations.
Their research suggests that the same approach could be applied to other aspects of human societies. “Since a simple model can model the essence of human interactions, we may be able to describe the essential dynamics that drive the evolution of other types of human social structures using similar simple models,” says Itao.
The study not only bridges physics and anthropology but also opens doors for exploring other cultural phenomena through simplified models. It highlights the profound impact of basic mathematical tools in unraveling the complexity of human behavior.