Cassava: From Toxic Tuber to Food Staple

By Christina Emery, Rachel Hirsch, and Melinda Susanto

When eaten raw, cassava is likely to leave a bitter taste in one’s mouth. Worse still, the unprocessed plant, containing high levels of cyanide, is poisonous to humans and can paralyze when eaten. Despite these deterring properties, cassava has long been culturally and nutritionally significant. And because Indigenous peoples of Meso- and South America discovered a way to render it edible through extensive processing, today cassava is enjoyed by 600 million people worldwide. One of the world’s major food crops alongside maize, rice, and wheat, cassava is cultivated as far away from its native habitat in South America as Southeast Asia. Nigeria is the world’s largest producer of cassava, where it is a primary source of carbohydrates for many and is consumed as part of a popular dish known as fufu.

How did cassava come to occupy this pride of place in the global food system? How did it transform from a poisonous tuber into a major food staple, and from an exclusive dweller of South America into a cosmopolitan citizen of the world? To answer these questions, this essay considers how human interactions with cassava helped to shape the plant into the significant food crop that it is today. We first look at the elaborate method of processing cassava developed by the Indigenous peoples of Meso- and South America and then turn to the codification and spread of this knowledge, facilitated by European travelers to the so-called New World. This meeting of Indigenous and European knowledge systems, combined with cassava’s tolerance for drought, resulted in a food crop that would create new hope for global food security in the twentieth and twenty-first centuries. Furthermore, as knowledge of cassava and its specimens circulated to different parts of the world, the plant took on additional cultural meanings through novel culinary uses and artistic representations.

Botanical drawing of cassava surrounded by caterpillars and other insects.
Drawing of cassava by Maria Sybilla Merian. Image Credit: Wellcome Collection

Of Frogs and Cassava: Early Cultivation in the Andes

Wild ancestors of the domesticated Manihot esculenta—known more commonly as cassava, manioc, or yuca—were likely introduced into Meso- and South-American agriculture by Indigenous farmers around 8000 BCE. Cassava was domesticated in these early agricultural plots, and the plant’s seeds and stem cuttings were traded over short distances.

Archaeological evidence suggests that cassava became an important food staple for several ancient cultures in present-day Peru, including the Chavin (1000–200 BCE), Nazca (200 BCE–600 CE), Moche (250–750 CE), and Chimú (1000–1470 CE).[1] 

Representations of cassava made by Moche artists provide clues as to how the plant was understood and appreciated by Andean peoples in the first millennium of the Common Era. Moche artists often represented cassava together with Leptodactylus pentadactylus—a frog found throughout the Amazon—as shown in this ceramic from Dumbarton Oaks’s collection. The smoky jungle frog, as this species is commonly called, was likely associated with agriculture, and representations of frogs may have been used in harvest-related rituals. Indeed, while cassava roots are the most commonly eaten part of the plant, they go bad quickly when dug up from the soil. However, if cassava is left in the ground, it can survive for up to four years and be harvested periodically.[2]

Indigenous Knowledge: How to Process Poison

While storing cassava in the soil addresses the issue of perishability, additional steps need to be taken to ensure that its roots can be safely eaten upon harvesting. In the Amazon, cassava is popularly divided into two major types—sweet and bitter—depending on the level of toxicity. Sweet cassava can be eaten simply by peeling and boiling it. Bitter cassava must be processed using a specific method before it can be safely consumed. The danger lies in cyanogenic glucosides, which vary in amount depending on the type of cassava, the climate, and the season in which it is cultivated. Women in Meso- and South America are primarily responsible for the processing of cassava and transforming the poisonous plant into flour for casaba, or cassava bread, and into a fermented beverage known as chicha. It is a multi-step process that includes washing and grating the cassava root, mashing it into a pulp, then hanging, dehydrating, and finally baking the dried pulp on a hot surface.[3]

1856 watercolor, “Saliva Indian Women Making Cassava Bread, Province of Casanare” by Manuel María Paz. Image Credit: Wikimedia Commons

Despite the amount of work required to process cassava with high levels of cyanide, bitter cassava is more popularly cultivated than sweet cassava in the Amazon today. The indigenous Tukanoans of the Yapu village in the northern Amazon, for example, grow 100 different types of cassava, 98 of which are bitter. Archaeologist Warren Wilson and anthropologist Darna Dufour have demonstrated that bitter cassava yields a higher harvest than does its sweet counterpart, possibly due to its resistance to disease and insects.  It is perhaps for this reason that bitter cassava is favored as a food crop over sweet cassava, despite the additional processing required to render it edible.

[1] Donald Ugent, Shelia Pozorski, and Thomas Pozorski, “Archaeological Manioc (Manihot) from Coastal Peru,” Economic Botany 40, no. 1 (1986): 99.

[2] Donna McClelland, “The Moche Botanical Frog,” Arqueología Iberoamericana 10 (2011): 40.

[3] Darna L. Dufour, “A Closer Look at the Nutritional Implications of Bitter Cassava Use,” in Indigenous Peoples and the Future of Amazonia: An Ecological Anthropology of an Endangered World, ed. Leslie E. Sponsel (Tucson: University of Arizona Press, 1995), 151.

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