The three staple crops that dominate modern diets in countries like the United States, Mexico and Brazil are corn, rice and wheat. However, fourth place is occupied by an underdog: cassava .
Although almost unknown in temperate climates, cassava is an important source of nutrition throughout the tropics – especially in Brazil. It was domesticated 10,000 years ago , on the southern margin of the Brazilian Amazon basin, and from there it spread throughout the region. With a shaggy stem a few feet tall, a handful of thin branches, and modest hand-shaped leaves, it doesn’t look like anything special . Cassava’s humble appearance, however, hides an impressive combination of productivity, resistance and diversity.
Over millennia, indigenous people transformed it from a weedy wild plant into a crop that stores prodigious amounts of starch in potato-like tubers, thrives in Amazonian soils and is nearly invulnerable to pests.
The many advantages of cassava seem to make it the ideal crop. But there’s a problem: Cassava is highly poisonous .How can cassava be so toxic and still dominate diets in the Amazon? It’s all down to indigenous ingenuity. For the past 10 years, my collaborator, César Peña, and I have been studying cassava plantations on the Amazon River and its numerous tributaries in Peru. We discovered dozens of cassava varieties, growers using sophisticated breeding strategies to control their toxicity, and elaborate methods to process their dangerous but nutritious products.
Long history of plant domestication
One of the biggest challenges early humans faced was getting enough to eat. Our ancient ancestors relied on hunting and gathering, catching fleeing prey and collecting edible plants at every opportunity. They were surprisingly good at it. So good that their populations have soared, leaving the birthplace of humanity in Africa 60,000 years ago .
Still, there was room for improvement. Scouring the landscape for food burns calories, the very resource being sought. This paradox forced hunter-gatherers to make a trade: burn calories foraging for food or conserve calories by staying home. The tradeoff was almost insurmountable, but humans found a way.
Just over 10,000 years ago, they overcame the obstacle with one of the most transformative innovations in history: domestication of plants and animals . People discovered that when plants and animals were domesticated, they no longer needed to be persecuted. And they could be selectively bred, producing larger fruits and seeds and bulkier muscles to eat.
Cassava was the champion domesticated plant in the Neotropical region . After its initial domestication, it spread throughout the region, reaching locations as far north as Panama within a few thousand years . Cassava cultivation did not completely eliminate the need for people to forage in the forest, but it lightened the burden, providing an abundant and reliable food supply close to home.
Today, almost every rural family in the Amazon has a vegetable garden. Visit any home and you’ll find cassava roasting over a fire, being toasted into a flat, chewy bread called casabe, fermenting in beer called masato, and cooking in soups and stews. However, before adopting cassava in these roles, people had to figure out how to deal with its toxicity.
Processing a poisonous plant
One of cassava’s most important strengths, its resistance to pests, is provided by a powerful defense system. The system is based on two chemical substances produced by the plant, linamarin and linamarase .
These defensive chemicals are found inside the cells of cassava leaves, stems and tubers, where they are generally inactive. However, when cassava cells are damaged, by chewing or crushing, for example, linamarin and linamarase react, releasing a burst of harmful chemicals.
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One of them is notorious: cyanide gas. The blast also contains other harmful substances, including compounds called nitriles and cyanohydrins. Large doses of these substances are lethal, and chronic exposures permanently damage the nervous system . Together, these poisons deter herbivores so well that yucca is nearly impervious to pests .
No one knows how people first solved the problem, but ancient Amazonians developed a complex, multi-step detoxification process that transforms cassava from inedible to delicious.
Women grind the starchy cassava tubers into pieces. Stephanie Maze/Corbis Historical via Getty Images
It begins with grinding the starchy cassava roots on chopping boards studded with fish teeth, rock chips or, more often these days, a rough sheet of tin. Grinding mimics the chewing of pests, causing the release of cyanide and cyanohydrins from the root. However, they are taken into the air, rather than into the lungs and stomach, as happens when they are ingested.
Next, the crushed cassava is placed in rinsing baskets, where it is washed, squeezed by hand and drained repeatedly. The action of water releases more cyanide, nitriles and cyanohydrins, and squeezing removes them.
Finally, the resulting pulp can be dried, which further detoxifies it, or cooked, which completes the process using heat. These steps are so effective that they are still used throughout the Amazon today, thousands of years since they were conceived .
A powerful culture ready to spread
The Amazonians’ traditional methods of grinding, rinsing and cooking are a sophisticated and effective means of converting a poisonous plant into a meal. However, the Amazonians went even further in their efforts, transforming it into a true domesticated culture. In addition to inventing new methods of processing cassava, they began to track and selectively cultivate varieties with desirable characteristics, gradually producing a constellation of types used for different purposes.
In our travels, we have encountered more than 70 distinct varieties of cassava that are highly diverse, physically and nutritionally. They include types that vary in toxicity, some of which need to be laboriously crushed and rinsed, and others that can be cooked as is, although none can be consumed raw. There are also types with different tuber sizes, growth rates, starch production and drought tolerance.
Their diversity is valued, and they are often given extravagant names . Just as American supermarkets have apples called Fuji, Golden Delicious and Granny Smith, Amazonian gardens have cassava called bufeo (dolphin), arpón (harpoon), motelo (turtle) and countless others. This breeding process consolidated cassava’s place in Amazonian cultures and diets, ensuring its ease of management and usefulness, just as the domestication of corn , rice and wheat consolidated their places in cultures elsewhere.
Although cassava has been established in South and Central America for millennia, its story is far from over. In the era of climate change and increasing efforts towards sustainability, cassava is emerging as a possible global crop . Its durability and resilience make it easy to grow in variable environments, even when soils are poor, and its natural resistance to pests reduces the need to protect it with industrial pesticides. Furthermore, although traditional Amazonian methods for detoxifying cassava may be slow, they are easy to replicate and speed up with modern machinery.
Furthermore, the preference of Amazonian producers to maintain different types of cassava makes the Amazon a natural repository of genetic diversity. In modern hands, they can be cultivated to produce new types, suitable for purposes beyond those of the Amazon itself. These advantages spurred the first export of cassava out of South America in the 1500s , and its range quickly spread to tropical Africa and Asia. Today, production in countries such as Nigeria and Thailand far exceeds the production of the largest producer in South America , Brazil. These successes are increasing optimism that cassava can become an environmentally friendly source of nutrition for populations around the world.
While cassava isn’t yet a household name in the U.S., it’s on the right track. It has long been unknown in the form of tapioca, a cassava starch used in puddings and boba tea. It’s also hitting shelves in the form of cassava chips and naturally gluten-free flour. Raw cassava is also an emerging presence, appearing under the names “yuca” and “manioc” in stores serving Latin American, African and Asian populations.
Find some and try it. The possibilities with cassava are almost endless .
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*This article is republished from The Conversation under a Creative Commons license. Read the original article.
