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Pre-colonial Amazonian people engineered the landscape and cultivated corn with advanced agrotechnology
New evidence reinforces that the Casarabe culture, which lived between 500 and 1400 C.E., built a complex drainage canal system in a region of the Bolivian Amazon marked by strong rainfall variability
Illustration depicting how agricultural tanks and drainage canals were likely used by the Casarabe culture for corn farming in the Bolivian Amazon – Photo: J.P. Guevara / Reproduction Nature
Over the past twenty years, archaeological studies have helped to uncover more of the ancient Amazon and its inhabitants’ unrevealed past. One of these cultures, the Casarabe, lived between 500 and 1400 C.E. in the southwestern Amazon region, more precisely in Llanos de Moxos, in the Beni department of Bolivia. Occupying about 4,500 square kilometers, the Casarabe carefully modified the local geography through earthworks and a complex settlement system that generated hundreds of monumental mounds – structures formed by rectangular platforms composed of four layers and conical pyramids reaching up to 22 meters in height.
“These sites have been known since the last century, but they began to be excavated more systematically in the late 1990s by a group of Germans and Bolivians. We know their chronology, the type of pottery they produced, but one thing that was still unclear was what they ate, what their dietary pattern was,” says Eduardo Góes Neves, an archaeologist and director of the Museum of Archaeology and Ethnology (MAE) at the University of São Paulo.
He is part of a group of researchers who have just confirmed the intensive production of corn in the area, as well as a sophisticated landscape engineering system for water drainage in corn farming in tropical savannas. The work was described in an article recently published in the journal Nature.
Archaeologist and USP professor Eduardo Góes Neves - Photo: Luiz Pereira Pinto/Ubu Editora
The study combined the use of LiDAR, a remote sensing technology that uses laser beams to identify potential excavation sites, with a program of sediment core drilling, radiocarbon dating, and analyses of pollen grains and phytoliths – microscopic mineral structures made of silica found in plant tissues that are preserved even after the plant decomposes.
According to the article, the system created by the Casarabe allowed some wet savannah areas to be converted into drained fields suitable for corn monoculture during the rainy season. “If you go there now, you’ll see that everything is flooded,” says Neves to Jornal da USP. “Since rainfall varies yearly, it was impossible to predict precipitation, so this strategy allowed them to ‘buffer’ the very drastic seasonal variation.”
Meanwhile, the construction of agricultural pond systems provided a water reservoir for irrigation in tanks, enabling the continuation of corn farming during the dry season, with up to two harvests per year.
“The savannah drains very slowly at the end of the rainy season, so people dug drainage canals to speed up this process. But when the dry season begins, the main constraint on agriculture becomes the lack of water, so they dug lakes, which retain water and allow agriculture to continue during the dry seasons as well,” adds Umberto Lombardo, a geomorphologist at the Universitat Autònoma de Barcelona in Spain, and the first author of the article.
Lombardo states that the intensive cultivation of corn likely allowed the population to grow. “We can safely assume that the population density of the Casarabe culture was higher than any other culture in the Amazon, perhaps except for the Upano Valley in Ecuador and Marajó in Brazil.”
The hypothesis is that the high availability of protein from corn cultivation, combined with other seeds like squash and beans, is associated with the emergence of hierarchical societies. However, the group did not find evidence of other crops besides corn.
“I’ve always defended the idea of polyculture in the Amazon. These data, in a way, somewhat contradict my hypotheses and show that, in Bolivia, there is a very strong correlation between the emergence of this monumental architecture pattern and corn cultivation,” says Neves.
Umberto Lombardo studies land surface forms and modifications of ancient landscapes – Photo: Springer Nature / personal archive
A Green revolution before Columbus
The type of agricultural system needed to sustain the Casarabe culture over its nearly thousand-year existence was still unknown, but the article highlights that the construction of drainage canals allowed the cultivation of fertile sediments from seasonally flooded savannas in the region of the monumental mounds of the Bolivian Amazon, without the need for deforestation of the forested portion.
The researchers found no evidence of cultivation or fire in the forested areas near the monumental mounds, suggesting that the Casarabe did not practice slash-and-burn agriculture. “Instead, this pre-Columbian culture likely preserved the spatially limited and therefore highly valuable forest resource for other important ecosystem services, such as firewood, construction materials, medicinal plants, and probably agroforestry,” the article emphasizes.
“The Amazon is a cradle of agrobiodiversity, many plants were first cultivated there. This is important because the savanna is like the Cerrado, a biome that can be interpreted as a place that is good for nothing. I don’t think the article will solve the world’s problems, but it shows that there wasn’t just one agricultural strategy and one way of life in the past” (Eduardo Neves).
For the researchers, the combination of these two types of landscape engineering – drainage canals and agricultural ponds – is unique to the monumental mound region and reveals a “pre-Columbian green revolution,” as well as “a highly innovative agricultural strategy that allowed the Casarabe culture to substantially increase the corn cultivation period, while also providing easy access to fish, birds, and game.”
The Beni savannah is an important ecoregion in Bolivia, characterized by vast wet plains – Photo: Sam Beebe - Wikipédia
Casarabe Culture
The Casarabe culture is named after a village near the archaeological sites discovered by researchers, who, in 2022, identified remnants of settlements spanning over 300 hectares. The site featured a large water management structure, spaces for human occupation, ceremonial activities, and burials.
There are records of human presence in this region of the Amazon dating back ten thousand years, but it is not known how the Casarabe culture began – nor why they transitioned from building small mounds to mega-structures. It is also unclear when they stopped practicing monoculture. “If we look at the isotopic data (atoms of the same element) in the most recent burials, the signal for corn becomes less pronounced. So, we need to understand whether corn was abandoned or if they became more polycultural and forest-dependent,” explains Neves.
He mentions the recent work of Brazilian archaeologist Tiago Hermenegildo, a USP graduate and currently a doctoral student at the Max Planck Institute in Germany. The research extracted carbon and nitrogen isotopes from the bones of 86 human remains of both sexes and various ages, identifying corn as a central element of the Casarabe diet.
“Personally, I think this Casarabe culture begins with changes in the Altiplano region, the emergence of Tiwanaku, which is an important political and religious center near Lake Titicaca and is a major city in the Andes,” says Neves. “I think the demand for trade in feathers, coca leaves, and other goods must have a connection to the emergence of these more centralized forms of political organization in the lowland region.”
The article Maize monoculture supported pre-Columbian urbanism in southwestern Amazonia is available at this link. The research is the result of a partnership between the São Paulo Research Foundation (Fapesp) and the Natural Environment Research Council (Nerc) of the United Kingdom.
For more information: umberto.lombardo@uab.cat, with Umberto Lombardo; edgneves@usp.br, with Eduardo Góes Neves
English version: Nexus traduções
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A reprodução de matérias e fotografias é livre mediante a citação do Jornal da USP e do autor. No caso dos arquivos de áudio, deverão constar dos créditos a Rádio USP e, em sendo explicitados, os autores. Para uso de arquivos de vídeo, esses créditos deverão mencionar a TV USP e, caso estejam explicitados, os autores. Fotos devem ser creditadas como USP Imagens e o nome do fotógrafo.