The impact of subsistence change on demography: Theory-informed Approximate Bayesian Computation reveals 4-fold increase in carrying capacity following economic intensification

Subsistence intensification is a major process in human history, however, quantifying its effects on demography is challenging given uncertainties regarding timing, population reconstructions, and ecological conditions. To help address these issues, we combine advances in ecological theory with Approximate Bayesian Computation (ABC) to generate a replicable, theory-informed, computational model for quantifying the effects of intensification on past population dynamics. Using the Colorado Plateau and Great Basin as case studies, we demonstrate how this ABC approach can 1) identify the timing of the adoption of intensified strategies to 2100 ± 117 and 2174 ± 395 cal BP, 2) show that intensification increased landscape carrying capacities by 4.1 ± 1 and 4.2 ± 1.9-fold, and 3) suggest that the process of intensification ranged over periods of 970 ± 244 and 1473 ± 416 years. In addition, the ABC method provides support for a core assumption of the ‘dates as data’ approach as only models built with simulated date sampling proportional to past population sizes are capable of matching observed output. Subsistence intensification has been tied to state formation, violence, inequality, sedentism, and numerous other influential phenomena. Our findings align with other prehistoric estimates from Europe and Africa to further suggest even this relatively small carrying capacity change coincides with significant social effects. • Approximate Bayesian Computation identifies timing and length of intensification. • Subsistence intensification increased carrying capacity of landscape 4-fold. • Subsistence intensification processes changed carrying capacity over ∼1000 years. • 4-fold population density increases correspond with drastic social change.