Researchers uncover new clues on the origins of agriculture

The invention of agriculture changed humans and the environment forever, and over several thousand years, the practice originated independently in a least a dozen different places. But why did agriculture begin in those places, at those particular times in human history?

Old stone axe used in agriculture [Credit: John Eisele/Colorado State University]

Using a new methodological approach, researchers at Colorado State University and Washington University in St. Louis have uncovered evidence that underscores one long-debated theory: that agriculture arose out of moments of surplus, when environmental conditions were improving, and populations lived in greater densities.

The first-of-its-kind study, "Hindcasting global population densities reveals forces enabling the origin of agriculture," published in Nature Human Behaviour, lends support to existing ideas about the origins of human agriculture. In contrast, they found little support for two other, longstanding theories: One, that during desperate times, when environmental conditions worsened and populations lived at lower densities, agriculture was born out of necessity, as people needed a new way of getting food. And two, that no general pattern exists, but instead the story of agriculture's origins is tied to unique social and environmental conditions in each place.

Senior author Michael Gavin, an associate professor in CSU's Department of Human Dimensions of Natural Resources, said the findings and the general methodological approach may help explain other watershed events in human history.

"There have been several key threshold events in our history that changed the entire course of our species," Gavin said. "Agriculture is a link to so many other components for what the world is like today for billions of people. This begins to help us explain a key moment in human history."

Studying the depths of human history is challenging, as little data are available when looking back tens of thousands of years. Scientists typically rely on archeological evidence, but getting a broad picture is difficult, since archaeological digs cover relatively small areas.

To overcome these limitations, the researchers modeled correlations between the environment, cultural traits and population densities of relatively recent foraging societies, which used hunting, fishing and gathering to obtain food.

Among the factors they considered as possible predictors of population density: environmental productivity; environmental stability; the average distance travelled when people in a community moved to a new location; whether people owned land or other resources; and distance to the nearest coast.