Drought is often blamed for the periodic disruptions of ancient Pueblo societies of the U.S. Southwest, but in a study with potential implications for the modern world, archaeologists found evidence that slowly accumulating social tension likely played a substantial role in three dramatic upheavals in Pueblo development. The findings show that Pueblo farmers often persevered through droughts, but when social tensions were increasing, even modest droughts could spell the end of an era of development.1
- 1. The research used tree-ring analyses of wood beams used for construction, which provided a time series of estimated tree-cutting activity spanning many centuries. "This record is like a social thermometer," said Kohler, who is also affiliated with the Crow Canyon Archaeological Center in Colorado and the Santa Fe Institute in New Mexico. "Tree cutting and construction are vital components of these societies. Any deviation from normal tells you something is going on." They found that weakened recovery from interruptions in construction activity preceded three major transformations of Pueblo societies. These slow-downs were different than other interruptions, which showed quick returns to normal in the following years. The archeologists also noted increased signs of violence at the same time, confirming that tension had likely increased and that societies were nearing a tipping point.
Marten Scheffer, Egbert H. van Nes, Darcy Bird, R. Kyle Bocinsky, Timothy A. Kohler. Loss of resilience preceded transformations of pre-Hispanic Pueblo societies. Proceedings of the National Academy of Sciences, 2021; 118 (18): e2024397118 DOI: 10.1073/pnas.2024397118
Abstract: Climate extremes are thought to have triggered large-scale transformations of various ancient societies, but they rarely seem to be the sole cause. It has been hypothesized that slow internal developments often made societies less resilient over time, setting them up for collapse. Here, we provide quantitative evidence for this idea. We use annual-resolution time series of building activity to demonstrate that repeated dramatic transformations of Pueblo cultures in the pre-Hispanic US Southwest were preceded by signals of critical slowing down, a dynamic hallmark of fragility. Declining stability of the status quo is consistent with archaeological evidence for increasing violence and in some cases, increasing wealth inequality toward the end of these periods. Our work thus supports the view that the cumulative impact of gradual processes may make societies more vulnerable through time, elevating the likelihood that a perturbation will trigger a large-scale transformation that includes radically rejecting the status quo and seeking alternative pathways.
Significance: Collapse of civilizations remains one of the most enigmatic phenomena in human history. In this paper we provide quantitative evidence that loss of resilience systematically preceded collapses. We take advantage of unique time series documenting both construction activity and climate conditions for pre-Columbian societies of the southwestern United States on an annual basis over a period of eight centuries. These data cover five transformations encompassing shifts to novel constellations of beliefs, social practices, and styles of art and architecture. The remarkable high-resolution time series allowed us to quantify the dynamics of social fragility using numerical techniques for probing resilience. Our results demonstrate that all but one of these transformations happened after decades of rising social instability.
