Events such as droughts, wars and natural disasters have repeatedly caused populations to shrink drastically throughout human history. But societies usually recovered from the setbacks over the course of decades to centuries. A study now uses historical records and archaeological data to show that the number of crises survived increases a population’s resilience to future setbacks. Accordingly, crises in particular could have contributed to promoting human population growth in the long term.
In ecology, it is believed that frequent natural disturbances help make an ecosystem more stable and resilient in the long term. However, it was still unclear whether something similar also applies to human populations. How do societies manage to deal with crises and recover from them? Which factors contribute to building social resilience that makes it possible to cope with setbacks and possibly even emerge stronger from them?
Historical consideration
A team led by Philip Riris from Bournemouth University in Great Britain approached these questions from a historical perspective. “Records of people’s past adaptations provide important insights for responding to future crises,” the research team writes. “We summarized resilience in a broad sample of prehistoric population data spanning 30,000 years of human history.”
As a basis, Riris and his colleagues used published studies that reconstructed for individual places and populations how the respective population developed over the course of thousands of years, when major population losses occurred and over what period of time society recovered from them . The current study summarizes data from 16 locations from different parts of the world. “Our global selection of regions extends from the Arctic to the tropics,” say the researchers.
Crises as opportunities
In total, the team recorded 154 major population losses, triggered by a wide range of events. These included environmental factors such as droughts and volcanic eruptions, social factors such as wars and colonialism, and mixtures of both, such as changes in dietary habits to adapt to changing environmental conditions. The information about these events came partly from historical records, partly from archaeological finds, climate models and sediment studies.
“The results show that a single factor, namely the frequency of past crises, increases both the ability to withstand disruptions and the ability to recover from them,” report the researchers. The more often a society has had to suffer setbacks in the past, the better it was able to deal with them. How quickly the recovery took place was subject to great fluctuations. Many populations took centuries to grow back to their original size, others managed to do so within decades.
Agriculture influences resilience
Riris and his team identified the nutritional habits of the respective population as a further influencing factor. “The global transition to a food-producing economy during the Holocene, which began in 11,700 B.P., not only increased the population’s vulnerability to disturbances, but at the same time also increased its ability to adapt through repeated exposure.”
Populations that rely on agriculture and livestock farming are more dependent on environmental factors such as precipitation and temperature. A single drought can trigger severe famine and cost many people their lives. Hunter-gatherer societies and populations that specialized in fishing experienced less fluctuation in this regard. In turn, agriculturally oriented societies developed strategies to deal with setbacks so that they were more resilient in the long term despite repeated disruptions.
“Population declines were potential triggers for investments in infrastructure, social cohesion and technological progress,” explain the researchers. “We suspect that humanity’s overall consistent long-term population growth may be due in part to the positive feedback between vulnerability, resilience and recovery documented here.”
Source: Philip Riris (Bournemouth University, Poole, UK) et al., Nature, doi: 10.1038/s41586-024-07354-8