Ancient civilizations actually stopped building their biggest monuments centuries before the climate even turned against them.
SSRN · March 18, 2026 · 6432696
The Takeaway
We often assume environmental disasters cause societal collapse. This study of Mississippi Valley mounds found that social reorganization and the abandonment of big construction happened hundreds of years before the actual climate shifts occurred.
From the abstract
This study examines the relationship between climatic variability and Middle Archaic (7000–4000 BP) mound building in the Lower Mississippi Valley by applying Bayesian changepoint modeling to 103 radiocarbon dates integrated with high-resolution paleoenvironmental proxies. Results show that demographic changepoints most often precede the strongest inferred climatic transitions at regional and local scales, with posterior probabilities exceeding 0.9 for several event classes. Posterior medians in