Simulation Shows Environmental Variability May Boost Evolution of Cooperation Among Humans

Researchers at the University of Tsukuba have shown through simulations based on evolutionary game theory that heightened environmental variability (EV) can promote the evolution of cooperation among humans. Their findings, published in the journal *PLOS Complex Systems*, shed new light on the variability selection hypothesis (VSH), which links the development of advanced cognitive abilities in humans to severe EV in Africa during the Middle Stone Age (MSA). The study extends the VSH to encompass the evolution of social behavior, a dimension that has been less explored in previous research. The MSA, a period marked by significant cultural and technological advancements, has long been viewed as a crucible for the development of complex human cognitive and social traits. However, the precise mechanisms that drove these evolutionary changes have remained unclear. The VSH suggests that the fluctuating environments of Africa during the MSA played a crucial role in enhancing individual cognitive abilities. But, this study proposes that EV also had a profound impact on the evolution of cooperative behavior. To test this hypothesis, the researchers created two models of EV: a regional variability model and a universal variability model. These models were designed to examine how changes in environmental conditions influenced cooperation among geographically distant groups. The regional variability model, which simulates localized changes in resource availability, was particularly revealing. It showed that resource scarcity in certain areas created new opportunities for cooperative strategies, thereby fostering the evolution of cooperation. In contrast, the universal variability model, where environmental changes were uniform across all regions, had a minimal effect on cooperative behavior. This distinction is significant because it suggests that EV alone is not enough to promote cooperation; the key factor is the differential distribution of resources across regions. When some areas experience resource scarcity while others do not, it encourages the formation of cooperative networks. These networks enable groups to share resources and survive in challenging environments, leading to a positive feedback loop where cooperation becomes more common and beneficial over time. The implications of these findings are far-reaching. They offer archaeologists a new framework for understanding the social dynamics during the MSA and highlight the importance of interregional resource distribution in the evolution of human cooperation. Moreover, the study provides insights into how modern societies might foster cooperation in response to large-scale crises and environmental changes, such as those caused by climate change. The research, led by Masaaki Inaba and his team, underscores the complex interplay between environmental factors and social evolution. By using multiagent simulation models, they have demonstrated that the geographical and temporal distribution of resources can significantly influence the development of cooperative behaviors. This approach not only enhances our understanding of ancient human sociality but also has practical applications in contemporary contexts, where cooperation is often essential for addressing global challenges. The study’s results, published in *PLOS Complex Systems* (2025), contribute to a growing body of research that explores the environmental and social dynamics of human evolution. They suggest that the variability in environmental conditions, rather than uniform changes, plays a critical role in shaping the ways in which humans interact and form cooperative relationships. This perspective could inform future research and policy-making, particularly in areas where resource management and social cohesion are crucial.