Rapoport’s rule and the biogeography of cultural diversity across North America over 13,000 years

A central goal of anthropology is to understand the drivers of human cultural diversity, and the archaeological record offers our most direct empirical window into the dynamics of that diversity through time. In this study, we investigate cultural diversity across North America over the past 13,000 years by analyzing spatiotemporal variation in the geographic ranges of bifacial point types. We demonstrate that much of this variation is structured by latitudinal gradients, and that the sensitivity of these gradients increases over time. We argue that the geographic ranges of point types represent the accumulated archaeological signature of cultural technological deposition by human populations adapting to latitudinally structured environmental conditions from the late Pleistocene through the late Holocene. These findings are consistent with Rapoport’s Rule, a widely observed—but still debated—biogeographic pattern in which species’ range sizes tend to increase with latitude. Our results also align with a growing body of research showing that various dimensions of human biological and cultural diversity—such as linguistic richness, economic development, and health disparities—exhibit similar latitudinal gradients at global scales. We explore how planetary-scale variation in temperature, energy availability, and environmental productivity—filtered through regional Earth systems—has shaped broad patterns in North America’s cultural evolutionary history, reflecting at least 13,000 years of dynamic human adaptation to shifting biophysical landscapes.