Repeated Demographic-Structural Crises Propel the Spread of Large-scale Agrarian States throughout the Old World

Abstract

I investigate the geographical consequences of demographic-structural dynamics using a spatially resolved agent-based model of agrarian empires in several Old World regions between 1500 BCE and 1500 CE. I estimate and bound key model parameters from two historical datasets. Although several very large-scale polities (e.g., Roman, Persian, Tang empires) do not arise and certain geographical expansions occur at different times, overall the model suggests that factional civil wars, the result of repeated internal demographic-structural crises, can substantially account for the spread of large-scale agriculture throughout the Old World after the Bronze Age.