Amazonia’s people domesticated crops on ‘forest islands’ 10,000 years ago: Study – Mongabay.com

  • Early Amazon human inhabitants domesticated and grew crops more than 10,000 years ago, making the region one of the world’s earliest centers of plant domestication for food, a study has found.
  • These early people left behind thousands of artificial raised forest islands in what is now the Llanos de Moxos savanna in northern Bolivia.
  • Researchers tracked glass-like microfossils to reveal evidence that these early farmers grew squash, corn and cassava.
  • The new research helps dispel a persistent myth that the Amazon long existed as a sort of wilderness paradise, largely untouched by human influences. Instead, it is now thought that humans have been profoundly altering the landscape of Amazonia for thousands of years, with lasting consequences for species conservation and habitats.

Amazonia, with its towering trees, bright birds, pink dolphins and mysterious big cats, has been painted as the quintessential wilderness, an exuberant and endless landscape that evolved beyond the touch of a cultivating human hand.

But in recent years, researchers began finding evidence that says otherwise. Bit by bit, a new picture of a long-established interrelationship between wild Amazonia and humankind has emerged.

Recently, new evidence was unearthed showing that early Amazon inhabitants domesticated and grew crops more than 10,000 years ago, transforming a part of what is today southwest Amazonia into an “archipelago” of fertile “forest islands” dotting the grassy savanna.

The region, in what is today northern Bolivia, is now thought to represent one of the world’s earliest centers of crop domestication, according to a recently published study in Nature.

Forest islands from above in the Llanos de Moxos savanna, Bolivia. Photo by Umberto Lombardo.

Scientists have found four far-flung locations around the world where they say crops were first domesticated, around 11,000 years ago. Rice was cultivated in China; potatoes and quinoa in the Andes; grains and pulses in the Middle East; and beans, squash and maize in Mesoamerica.

“This research helps us to prove Southwest Amazonia is likely the fifth,” Jose Iriarte, a study author from the University of Exeter, said in a statement.

The 4,700 artificial forest islands, believed to be built gradually by humans, speckle the seasonally flooded Llanos de Moxos savanna in northern Bolivia. When the region floods, these islands remain above the water.

“These are just places where people dropped their rubbish, and over time they grow,” said lead author Umberto Lombardo from the University of Bern. “Of course, rubbish is very rich in nutrients, and as these areas grow they rise above the level of the flood during the rainy season, so they become good places to settle with fertile soil, so people come back to the same places all the time.”

Isla Manechi, the forest island in the Barba Azul Nature Reserve, Bolivia, where the oldest evidence for cassava and squash was found. Photo by Umberto Lombardo.

The research team used remote sensing to map large sections of the savanna, and then “ground-truthed” 30 of the forest island sites. The team collected radio-carbon-dated sedimentary cores from all the sites and conducted archaeological excavations at four.

The scientists searched within the soil cores for telltale signs of ancient crops in the form of tiny glass microfossils. Plants, as they grow, produce glass-like silica particles called phytoliths inside their cells. The various shapes of phytoliths are unique to particular plant types and can remain in the soil for thousands of years, long after the original specimen has decayed. The identifying phytolith shapes, along with their locations in the sediment core, allow scientists to estimate what plants were grown at what times.

The phytolith remains found at the island sites offered strong evidence that early Amazonian inhabitants grew squash, maize and cassava. Squash (Cucurbita spp.) phytoliths were discovered in soil cores as far back as 10,250 years before present (YBP); cassava (Manihot spp.) 10,350 YPB; and maize (Zea mays) 6,850 YBP.

“The evidence we have found shows the earliest inhabitants of the area were not just tropical hunter-gatherers, but colonizers who cultivated plants. This opens the door to suggest that they already ate a mixed diet when they arrived in the region,” Iriarte said.

The thinking is that the diet of these early people consisted mostly of squash, corn, sweet potatoes, peanuts and other carb-rich foods, supplemented by fish and meat, according to the researchers. It’s hypothesized that the ancient farmers may have brought these plants with them as they migrated from farther north.

José Capriles, assistant professor of anthropology at Penn State, during excavations in the San Pablo forest islands. Image courtesy of José Capriles/Penn State.

This research adds to the growing body of evidence now suggesting that Amazonia is not a pristine wilderness, but rather a mosaic of wild lands and cultivated gardens. People have profoundly altered the landscape of Amazonia for thousands of years, with lasting consequences for species conservation and habitats.

As far back as 8,000 years ago, people living in the Amazon rainforest favored and cultivated certain useful tree and other plant species, according to a massive 2017 study.

Domesticated species such as Brazil nuts and cocoa were five times more likely than other species to dominate the landscape — especially along rivers, which people used then as roads and which were dotted with settlements. Modern tree communities in the Amazon, the 2017 research says, have been structured to some degree by human domestication of plants.

In a more recent study, new evidence was found of innovation by ancient farmers in the headwaters of the Xingu River Basin in southern Amazonia dating back to the pre‐Columbian period. Farmers there enriched tropical soils using charcoal and compost, creating fertile planting zones called “dark earth areas” that increased overall species richness.

Areas of fertile dark earth found deep in the soil in the Xingu River Basin in southern Amazonia.  Photo by Ben Hur Marimon Junior.

In fact, a Mongabay reporting team visiting the Iriri River Basin, near the Xingu, in 2016 met with traditional riverine people who showed them in situ artifacts of unknown age in the rainforest that included pottery shards, ax heads, and dark black soil they called terra preta — enriched earth ideal for crops, supposedly created by unknown indigenous predecessors. Researchers think that this charcoal-composting soil-enrichment technique may have once been practiced throughout the Amazon.

“We think ancient communities used dark earth areas to grow crops to eat, and adjacent forests without dark earth for agroforestry,” Beatriz Marimon, a professor at the State University of Mato Grosso, said in a statement. “Dark earth increases the richness of species, an important consideration for regional biodiversity conservation.”

Taken together, these findings highlight the legacy of early human inhabitants and their interactions with, and influences on, the evolution of native vegetation, soil, and Amazon biodiversity.

Citations:

Lombardo, U., Iriarte, J., Hilbert, L., Ruiz-Pérez, J., Capriles, J. M., & Veit, H. (2020). Early Holocene crop cultivation and landscape modification in Amazonia. Nature581(7807), 190-193. doi:10.1038/s41586-020-2162-7

Stephens, L., Fuller, D., Boivin, N., Rick, T., Gauthier, N., Kay, A., … Ellis, E. (2019). Archaeological assessment reveals Earth’s early transformation through land use. Science365(6456), 897-902. doi:10.1126/science.aax1192

de Oliveira, E. A., Marimon‐Junior, B. H., Marimon, B. S., Iriarte, J., Morandi, P. S., Maezumi, S. Y., … Feldpausch, T. R. (2020). Legacy of Amazonian Dark Earth soils on forest structure and species composition. Global Ecology and Biogeography. doi:10.1111/geb.13116

Banner image of cassava starch by Neil Palmer (CIAT) (CC BY-SA 2.0).

Liz Kimbrough is a staff writer for Mongabay. Find her on Twitter @lizkimbrough_

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