What Drives Societal Collapse?


It was generally thought that climate during the last 11,000 years was monotonous and benign, allowing human societies to develop agriculture. The many instances of collapse of prehistoric and early human societies were thought to be caused by social, economic and political factors; the role of climate in such collapses has been conspicuously absent from the discussion until recently.

In the last twenty years much new information has come to light about ancient climates. It turns out the climate during much of human history has had major mood swings: continent-wide droughts that lasted for tens to hundreds of years have been documented.

Early agriculture-based societies were vulnerable to changes in the climate. When the history of past climates is compared to the archaeological records of early societies a pattern emerges: early societies often collapsed at the same time there was a significant drought. For instance, about 10,000 B.C. the Natufian peoples in southwest Asia abandoned hunting and gathering for an agricultural way of life. Agriculture allowed for large increases in population, class formation, craft specialization; that is, the early development of our civilization. However, about 6,400 B.C. a 200-year drought hit the region, and the Natufians abandoned their settlements and dispersed.

Wetter conditions eventually returned to the eastern Mediterranean around 3,000 B.C. and politically centralized and class-based urban societies again appeared in west Asia and the Mediterranean basin. These included the Akkadian peoples of Mesopotamia; the pyramid-building Old Kingdom of Egypt; and the early Bronze Age civilizations of Palestine, Greece, and Crete. These societies all collapsed around 2200 B.C., the same time that an abrupt, intense drought extended from Greece to western India.

A similar story can now be told about early societies in the New World. In the sixth century A.D. the Moche peoples of northern coastal Peru were hit by a thirty-year drought, and in the ninth century A.D. the Classic Maya empire disappeared when the most severe and prolonged drought of that millennium occurred.

Not all social collapses have been due to climate change, but data now show that climate has played a more important role in the human story than we previously recognized. We spoke with Harvey Weiss and Raymond Bradley, the authors of a recent Science article about climate change and societal collapse.

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