Modeling the rise and demise of Classic Maya cities: Climate, conflict, and economies of scale

Urbanization was one of the most significant transitions in human history, yet explanations for the rise and expansion of early cities remain contentious. Here, we propose that simple models from population ecology can integrate existing theories for the development of early cities. Using newly synthesized paleoclimatological, paleoecological, demographic, and historical data from across the Classic Period Maya Lowlands (250-1000 CE) integrated with piece-wise structural equation models, we show that climate downturns, intergroup conflict, and strong economies of scale interact to promote the coevolution of urbanism and patron-client relationships, fueling city expansion, urban institutions, and systemic inequality. In addition, we elucidate how these nonlinear pathways structure the persistence or dissolution of cities. This study underscores the importance of robust economies of scale in the development of early cities and provides a comprehensive framework for understanding the conditions that promote or hinder urbanization, offering insights applicable to both ancient and contemporary urban dynamics.