An analysis of ancient human and animal remains suggests that pre-colonial peoples in the Bolivian Amazon likely fed ducks more than a 1,000 years ago, a study reports.
The research, published in the journal Nature Human Behavior, also indicates that these populations were largely reliant on maize agriculture during certain periods.
Taken together, these findings cast light on how ancient humans interacted with Amazonian ecosystems, while providing direct evidence for the management of animals in pre-colonial times.
Over the past decade or so, multidisciplinary research has transformed our understanding of the history of the Amazon Basin. Previously, the region was seen as largely unfavorable for food production and large-scale human societies in ancient times.
But recent studies have started to uncover evidence for the existence of low-density urban societies, as well as the domestication and management of various plant species—such as cassava, squash, sweet potatoes, yams and, in particular, maize—in certain areas of the forest stretching back thousands of years.
Despite this, "direct insights" into human interactions with certain crops and especially animals remain scarce across the vast Basin area, which covers roughly 2.7 million square miles of the South America continent. This lack of evidence is particularly the case in parts of the Bolivian Amazon once inhabited by the Casarabe people.
This pre-colonial culture, dated between A.D. 500–1400, is known for the nearly 200 large, monumental mounds it constructed across the Llanos de Mojos region, interconnected through roughly 600 miles of canals and causeways.
"The sheer volume of sites and their architectural layout, divided into a four-tier settlement system—ranging from large primary centers (150–300 hectares) to small forest islands (around 0.3 hectares)—indicate that the people of the Casarabe culture created a new social and public landscape through monumentality, leading to low-density urbanism," the authors wrote in the paper.
In their study, the researchers analyzed the bone remains of 86 humans (both male and female) and 68 animals (including bird, fish, mammal and reptile species) found at a site in Llanos de Mojos associated with the Casarabe culture. The remains date to between A.D. 700 and A.D. 1400.
The work involved what scientists call a "stable isotope analysis"—which examines the ratios of specific isotopes preserved in ancient bones and teeth to shed light on diet and environmental interactions. Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.
Different plants and animals have distinct isotope signatures. By analyzing these, researchers can determine what types of food ancient people or animals consumed, offering valuable insights into their ecological roles and subsistence practices.
The team's analysis revealed that maize was a common component of the human diet for all of the sampled individuals.
The data indicated that peak consumption of maize occurred between around A.D. 700 and A.D. 800 when these populations appeared to rely on the crop, before a reduction in its dietary importance occurred between A.D. 1100 and 1400.
Among the animal remains analyzed were those of muscovy ducks—a type of large waterfowl native to Central and South America. The team's work revealed that the ducks in the sample appear to have been intentionally fed maize as early as A.D. 800—and may have even been domesticated by around this time.
"Muscovy ducks are known for being the only domesticated vertebrate in all of the lowlands of South America, evident in the archaeological record and in colonial accounts of domesticated muscovy ducks in the Llanos de Mojos; however, understanding of this process has remained largely unknown," the authors wrote.
"The data presented here provide support that humans were feeding and keeping muscovy ducks in the Bolivian Amazon from as early as [A.D.] 800 while also highlighting the role of maize in the domestication process."
The steady decline in the reliance on maize as a staple crop after A.D. 800 that the authors observed could be an indication that the Casarabe people began diversifying their agricultural practices or started increasing trade with other populations.
Maize was already being grown in the Bolivian Amazon prior to the emergence of the Casarabe culture around A.D. 500, but the crop likely enabled this group to expand as it became a staple in the diet, according to the authors.
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Reference
Hermengildo, T., Prümers, H., Jaimes Betancourt, C., Roberts, P., O'Connell, T. C., (2024). Stable isotope evidence for pre-colonial maize agriculture and animal management in the Bolivian Amazon. Nature Human Behaviour. https://doi.org/10.1038/s41562-024-02070-9
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