A set of factors have been found that preceded population crashes in Europe thousands of years ago. If the peoples of the time had been aware of their significance, perhaps they could have taken evasive action. It’s far too late for those long-gone cultures, but some of the same signs could be very relevant today.
The study of regime shifts has become a major component of ecology in recent decades. Such shifts are usually preceded by declining resilience, or the capacity to maintain the health of a system. The markers of declining ecological resilience have been extensively cataloged. The understanding developed from ecosystem research has been applied to other complex systems, including human society, but it has proven much harder to identify the early warning signals (EWSs) for social systems.
Dr Sean Downey of the University of Maryland may have changed that. He has developed a set of EWSs, and shown they occurred prior to at least seven population collapses in Europe between 4,000 and 8,000 years ago, an era known as the Neolithic.
Downey chose nine well-studied regions of Europe and used data from more than 2,000 archaeological sites, with over 13,000 individually dated items. Population changes over time were estimated from the ratio of newly founded villages to old abandoned ones. Each region saw relatively steady population growth over many centuries after the introduction of agriculture. Eventually, however, all nine suffered at least one crash, losing up to 60 percent of the population in the course of a century.