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Ageing societies become vulnerable

Societies become increasingly fragile over their lifetime, according to research by scientists from Europe, China, and the USA published in the journal Proceedings of the National Academy of Sciences this week.

Published 20th November 2023

The work is based on patterns in 324 pre-modern states, but similar mechanisms may be at work today.

Humans become increasingly fragile as they age. Now an international team of scientists showed that something similar happens to states.

Triggers of the collapse of societies are well studied and may vary from conquest and coups to earthquakes and droughts.

However, the new work shows that such perturbations are not the whole story.

The results reveal that the risk of state termination increased steeply over the first two centuries after formation.

This provides the first quantitative support for the hypothesis that the resilience of political states decreases over time.

Several mechanisms could drive such ageing effects, but candidates include mechanisms that are still at work today such as environmental degradation and growing inequity.

How states and great powers rise and fall is an intriguing enigma of human history.

In this study the authors took a fresh angle on this question.

They analysed longevity in hundreds of premodern states spanning millennia of data.

“This approach is commonly used to study the risk of death in ageing humans, but nobody had the idea to look at societies this way,” said Marten Scheffer, lead author of the paper.

“Yet the idea makes a lot of sense, at least when sufficient data are available.

“The idea emerged when we saw a striking BBC representation of the work by Luke Kemp from Cambridge University picturing the rhythm of rise and fall over millennia.”

In humans, the risk of dying approximately doubles ever 6-7 years.

As that exponential process explodes at high age, few people survive longer than 100 years.

The authors showed that it works differently for states.

Their risk of termination rises steeply over the first two centuries, but then saturates, allowing a few to persist much longer than usual.

Co-author Professor Tim Lenton, from the Global Systems Institute at the University of Exeter, said: “As our society enters a climate and ecological crisis of our own making, the evidence that it is getting less resilient just increases the systemic and existential risks we are facing.

“A glimmer of hope is that some past societies pulled through crises and lived much longer – but they had to reinvent themselves in the process.”

Societies today differ in many ways from the pre-modern states studied by the authors.

Nonetheless, according to Scheffer: “We cannot expect our modern societies to be immune to the mechanisms that drove the wax and wane of states for millennia.

“Mechanisms that destabilised past societies remain relevant today.

“Indeed, perceived unfairness and scarcity exacerbated by climatic extremes may still drive discontent and violence.”

The paper is entitled: “The vulnerability of aging states: a survival analysis across pre-modern societies”.