(CN) — A novel study Wednesday of 61 archaeological sites in the Amazon confirms researchers’ long-held belief the biodiverse rainforest region is one of the earliest places humans domesticated food crops, after finding the presence of manioc, squash and maize.
The findings posit the southwestern Amazonia region as the fifth area worldwide where ancient staple food crops were originally domesticated. The others include rice in China; grains and pulses in the Middle East; maize, beans and squash in Mesoamerica; and potatoes and quinoa in the Andes.
In a study published in the journal Nature, researchers found the earliest humans to inhabit the Amazon 10,000 years ago created thousands of artificial forest islands to support the cultivation of wild plants — including manioc and squash — for food.
The creation of 4,700 forest island “mounds” in what is now Llanos de Moxos in northern Bolivia promoted landscape diversity in the savannah area, which floods from December to March and is extremely dry from July to October, the study found.
Because the mounds remain above the water level during the rainy season, trees could grow and supported small-scale communities in the Amazon 8,000 years earlier than previously thought.
Jose Capriles from Pennsylvania State University was one of the researchers to conduct the study. In an interview, he said while the Amazon is thought of as a “pristine rainforest,” people have affected the richness of the biodiversity over time, creating “nutrient hotspots” when planting the islands.
He said the study is the first to find “concrete proof” for researchers’ hypotheses many of the most important domesticated crops come from wild plant species in the Amazon region.
“There’s increasing evidence that’s really demonstrating humans were present in Amazonia and doing interesting, creative things and experimental work with managing the landscape,” Capriles said.
“People had the knowledge to cultivate food and there were enough people there to create population pressure to require innovating,” he added.
Researchers analyzed microscopic plant silica bodies, called phytoliths, which were found well-preserved in the tropical forests.
The evidence showed manioc – the cassava or yuca root – from 10,350 years ago, squash from 10,250 years ago and maize – corn – from 6,850 years ago was planted in the Amazon. The plants were grown on the forest islands because they are carbohydrate-rich and easy to cook, likely providing most calories consumed by the first Amazon inhabitants and supplemented by some fish and meat, according to the study.
“Archaeologists, geographers, and biologists have argued for many years that southwestern Amazonia was a probable center of early plant domestication because many important cultivars like manioc, squash, peanuts and some varieties of chile pepper and beans are genetically very close to wild plants living here,” researcher Dr. Umberto Lombardo said in a statement.
“However, until this recent study, scientists had neither searched for, nor excavated, old archaeological sites in this region that might document the pre-Columbian domestication of these globally important crops,” he added.
Researchers analyzed 61 archaeological sites – identified by remote sensing – which are now patches of forest surrounded by savannah. They also retrieved samples from 30 forest islands, carrying out archaeological excavations in four of them.
Capriles said crop biodiversity remains important for the Amazon region, noting the impact monocropping, or the practice of growing a single crop year-after-year on the same land, had in causing thousands of fires last year to burn through the rainforest in Brazil and Boliva where farmers were clearing land to plant soybeans or raise cattle.
“People there for several thousand years shows you can engage in biodiversity while using sustainable practices,” Capriles said.
The Brazil-based National Institute for Space Research found an 83% increase in fires in the Amazon in 2019, where deforestation has increased by nearly 300%.