Tropical lowlands that flood during the rainy season and scorch during the sunny season don’t exactly sound ideal for agriculture. But the people who lived in what is now Bolivia between 500 A.D. and 1400 A.D. turned those conditions to their advantage by engineering a system of canals to divert excess water and ponds to save it for later.

By building a sophisticated irrigation network, the pre-Hispanic Casarabe society of the Llanos de Moxos produced maize year-round — ushering in a Neolithic Revolution based on a single grain, according to a report in Nature. This finding contradicts earlier theories that a monoculture was not part of that area’s lifestyle.

Watering an Agricultural Revolution

Although archeological evidence supports maize farming at least 6,800 years ago in Amazonia and 4,000 years back in Mesoamerica, investigation of the Bolivian site provides the first solid evidence of one society relying primarily on a single crop. The society’s ability to both divert and store excess water allowed them to harvest at least two maize crops a year. That meant a reliable year-round food source that could support a relatively large society.

“This intensive agricultural strategy indicates that maize was not only cultivated but was likely the staple crop of the Casarabe culture,” Umberto Lombardo, an archaeologist at the Universitat Autònoma de Barcelona and an author of the paper, said in a press release.

Read More: A Massive, Ancient Network of Cities Flourished in the Amazon for 1,000 Years

Early Signs of Sustainability

Also unusual for the time, archeologists investigating the site found no evidence of slash and burn techniques that other societies used to first clear forests, then fertilize the new fields with ashes. Instead, the Casarabe people likely tapped into the preserved forests for firewood and medicinal plants.

The team conducted extensive analysis of the site to reconstruct the complex system of canals and storage ponds. They analyzed 178 plant microfossils to confirm that maize indeed dominated farming there.

“The data shows the absence of other types of crops,” according to Lombardo.

Neolithic Food Stability

Lombardo asserts that this innovative piece of engineering allowed for the transformation of a challenging environment into a productive system that ensured food stability and supported the development of a growing population.

“We can document that this is the first grain-based agrarian economy in the Amazon, where until now it was believed that agriculture was based on agroforestry polyculture and not on large-scale monocultures. Now we know that this was not the case in Llanos de Moxos,” says Lombardo.

A reliable food source likely allowed the region to both grow and prosper. “Collectively, our findings show how the Casarabe culture managed the savannah landscape for intensive year-round maize monoculture that probably sustained its relatively large population,” according to the paper. “Our results have implications for how we conceive agricultural systems in Amazonia, and show an example of a Neolithic-like, grain-based agrarian economy in the Amazon.”

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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.