As extreme weather events become more prevalent due to human influence on the global climate system, an increasingly salient question involves factors that enhance societal resilience. In a new paper published in the journal Nature, Philip Riris and colleagues synthesized radiocarbon measurements from sixteen different archaeological traditions spanning 30,000 years to track episodes of population growth and decline. They found that societies that experienced more frequent downturns in previous time steps tended to recover faster and more strongly in the current time step.
In New York Times coverage of the work, Riris speculates that the reason for this pattern is that during downturns societies learn how to survive, and then they pass that knowledge down to future generations. Such experiences “led to innovations — or technologies or practices or behaviors or know-how or traditions — being adopted that enabled them to do better the next time something bad rolled around.”
A key follow-on question is what insights such broad patterns in the archaeological record offer for improving societal resilience today? This will take additional work, and perhaps the forthcoming design workshop on urban adaptation to environmental change will take this up. In the meantime, I will indulge in some additional speculation. It is well-known from evolutionary studies that genetic diversity within a population promotes evolvability and adaptability. Genetic variation makes certain individuals pre-adapted to possible future states of the environment, thus making it easier for the population to adjust its biology to whatever future state actually occurs. Genetic variation is typically measured cross-sectionally, across individuals living at a given moment. But it can also be measured over time, in the form of temporal variation in the genetic composition of a population across generations. If spatial and temporal variation are generally correlated, then measuring one would imply the existence of the other.
Translated to human social life, one might expect variation in demographic rates, reflected in summed probability distributions of radiocarbon dates, to reflect variation in adaptive strategies across space as well. If so, societies that maintained diverse adaptive strategies, as opposed to optimizing on one strategy, might be expected to do better when they faced new challenges. We know that it is very difficult for individual investors to outperform index funds in the stock market. Perhaps the archaeological record is showing something similar at societal scales? If so, one might expect societies that had more diverse radiocarbon probability surfaces over previous time periods to have been more resilient in the current period as well.
If in fact diversity, however measured, is the raw material of resilience, this realization would seem to have important implications for public policy and for individual decisions today. I have no idea if these speculations hold water, but archaeologists should be able to determine whether they are right or wrong through additional studies like this one. Here’s hoping that someone will take this on!