Oasis Theory - Did Climate Change Cause the Invention of Agriculture?

Did Desiccation at the End of the Pleistocene Cause the Invention of Farming?

Flour Mill at the Dajla Oasis,, Egypt
Flour Mill at the Dajla Oasis, Egypt. Ernesto Graf

The Oasis Theory (known variously as the Propinquity Theory or Desiccation Theory) is a core concept in archaeology, referring to one of the main hypotheses about the origins of agriculture: that people started to domesticate plants and animals because they were forced to, because of climate change.

The fact that people changed from hunting and gathering to farming as a subsistence method has never seemed like a logical choice.

To archaeologists and anthropologists, hunting and gathering in a universe of limited population and plentiful resources is less demanding work than plowing, and certainly more flexible. Agriculture requires cooperation, and living in settlements reaps social impacts, like diseases, ranking and social inequality, and division of labor.

Most European and American social scientists in the first half of the 20th century simply didn't believe that human beings were naturally inventive or inclined to change their ways of life unless compelled to do so. Nevertheless, at the end of the last Ice Age, people did reinvent their method of living.

What Do Oases Have to Do With That?

The Oasis Theory was defined by Australian-born archaeologist Vere Gordon Childe [1892-1957], in his 1928 book, The Most Ancient Near East. Childe was writing decades before the invention of radiocarbon dating and a half century before the serious collection of the vast amount of climatic information that we have today had begun.

He argued that at the end of the Pleistocene, North Africa and the Near East experienced a period of desiccation, a period of increased occurrence of drought, with higher temperatures and decreased precipitation. That aridity, he argued, drove both people and animals to congregate at oases and river valleys; that propinquity created both population growth and a closer familiarity with plants and animals.

Communities developed and were pushed out of the fertile zones, living on the edges of the oases where they were forced to learn how to raise crops and animals in places that were not ideal.

Childe was not the first scholar to suggest that cultural change can be driven by environmental change--that was American geologist Raphael Pumpelly [1837-1923] who suggested in 1905 that central Asian cities collapsed because of desiccation. But during the first half of the 20th century, the available evidence suggested that farming appeared first on the dry plains of Mesopotamia with the Sumerians, and the most popular theory for that adoption was environmental change.

Modifying the Oasis Theory

Generations of scholars beginning in the 1950's with Robert Braidwood, in the 1960's with Lewis Binford, and in the 1980's with Ofer Bar-Yosef, built, dismantled, rebuilt, and refined the environmental hypothesis. And along the way, dating technologies and the ability to identify evidence and timing of past climate change blossomed. Since then, oxygen-isotope variations have allowed scholars to develop detailed reconstructions of the environmental past, and a vastly improved picture of past climate change has been developed.

Maher, Banning, and Chazen recently compiled comparative data on radiocarbon dates on cultural developments in the Near East and radiocarbon dates on climatic events during that period. They noted there is substantial and growing evidence that the transition from hunting and gathering to agriculture was a very long and variable process, lasting thousands of years in some places and with some crops. Further, the physical effects of climate change also were and are variable across the region: some regions were severely impacted, others less so.

Maher and colleagues concluded that climate change alone cannot have been the sole trigger for specific shifts in technological and cultural change. They add that that doesn't disqualify climatic instability as providing the context for the long transition from mobile hunter-gatherer to sedentary agricultural societies in the Near East, but rather that the process was simply far more complex than the Oasis theory can sustain.

Childe's Theories

To be fair, though, throughout his career, Childe didn't simply attribute cultural change to environmental change: he said that you had to include significant elements of social change as drivers as well. Archaeologist Bruce Trigger put it this way, restating Ruth Tringham's comprehensive review of a handful of Childe biographies: "Childe viewed every society as containing within itself both progressive and conservative tendencies which are linked by dynamic unity as well as by persistent antagonism. The latter provides the energy that in the long run brings about irreversible social change. Hence every society contains within itself the seeds for the destruction of its present state and the creation of a new social order."