Yuca and cazabi: a poisonous root, an indigenous detoxification press, and the bread that kept a year at sea
Bitter cassava kills whoever eats it raw. The Taíno of Hispaniola had a processing chain that made it the bread of the Caribbean, and Oviedo, a royal official on the island, printed the whole procedure in 1535 — the grater, the woven çibucan press, the hanging stones, the burén griddle, the poisonous juice poured on the ground — with the price of a load in Santo Domingo and the note that cazabi kept a year at sea. Modern genetics places the domesticate on the southern rim of the Amazon.
Why this wins its question: English-language accounts of cassava say that indigenous peoples "processed it to remove the cyanide" and move on; the actual procedure, and the fact that a sixteenth-century Spanish official printed it in full, is almost never quoted. This object gives the chain step by step from the page — shell, grater, çibucan of woven bark, windlass and hanging stones, the poison poured on the ground, the burén — with the Taíno words the Spanish text preserves (conuco, çibucan, buren, xauxau, boniata), and then prices it: a load of two arrobas at a ducado in Santo Domingo, keeping a year at sea. It sets that beside the two things such accounts leave out in opposite directions: Oviedo recording in 1535 that the sweet-and-sour uses of the juice were already being forgotten because the elders were dead, and the modern neurology of konzo showing what the same shortcut costs today. And it says plainly that the crop's global career ran through Portuguese ports, not Spanish ones.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
Oviedo gives cassava bread a chapter of its own in the book of his Historia general y natural de las Indias devoted to agriculture, and the chapter heading states both what it is and who was eating it: "Del pan de los indios que se llama caçabi, que es la segunda manera de pan que en esta Isla Española é otras partes haçen los indios, y al pressente assi mismo los chripstianos, y aun algunos lo usan mas que el mahiz, é lo tienen por mejor é se sirven mas dello, lo qual se haçe de una planta que llaman yuca" (libro VII, capítulo II, p. 268). The text opens by extending the range: the bread is made "en esta Isla Española, y en las otras todas que están pobladas de chripstianos, y aun en alguna parte de la Tierra-Firme".
The plant is described as farmed, not gathered, and the field has its own Taíno name in the Spanish text: the cuttings go into round earth mounds set out in rows "como en el reyno de Toledo ponen las viñas, y en especial en Madrid, que se ponen las çepas á compás", each mound eight or nine feet round and knee high, taking six, eight, ten or more pieces of stem, and the plot has to be kept weeded — "es menester yr deshervando el conuco (que assi se llama conuco la haça ó heredad de la yuca é de la labrança)". Planting follows the moon: "Siémbrasse ó pónesse siempre, despues que la luna ha hecho é se muestra nueva ... pero nunca en la menguante" (p. 269).
The danger is stated without euphemism. Any man or animal, save three exceptions Oviedo names, that eats the roots with their juice "assi en fructa, como está antes que se le saque el çumo (en çiertas prenssas), luego muere sin remedio alguno"; the exceptions he allows are cows, mice "é aun caballos". He also distinguishes the varieties: "en la Tierra-Firme hay yuca que no es mortal, é no mata", while on Hispaniola and the neighbouring islands "toda la yuca que hay, por la mayor parte, es de la que mata", with some of the sweet kind "que llaman boniata" (p. 269). That distinction between bitter and sweet cassava is the one the crop is still classified by.
The detoxification chain is printed in full, and it is Taíno technology described by an outsider watching it work: after "los indios é indias" have scraped off the bark with clam shells so that none remains, they grate the peeled root on rough stones and graters kept for the purpose, throw the pulp into a clean trough and fill with it a çibucan, "una talega luenga de empleyta, hecha de corteças de árboles blandas, texida algo floxa, de labor de una estera de palma", ten or twelve palms long and as thick as a leg. The tube is hung from a wooden lever with a windlass, heavy stones are tied to its lower end, and the windlass stretches it and lifts the stones into the air "de tal manera, que se estruja y exprime la yuca é le sale todo el çumo ... hasta que no le queda á la yuca gota de çumo ó mosto. É aquesta agua ó licor es pestífero veneno, é se vierte é pierde por el suelo". What stays inside the press, dry "como suelen quedar unas almendras exprimidas mucho", is then baked on a burén, "una caçuela llana de barro é tan grande quanto un harnero é sin paredes", set over a fire that never touches it (p. 270).
Two details on the same page cut against any reading of the transfer as European instruction. Oviedo records that Spanish soldiers experienced in the islands "han enseñado en Tierra-Firme á haçer pan de la yuca que no mata; pero no curan dello, por no perder tiempo" — the teaching concerns the harmless variety, it was declined, and the lethal kind is not what they taught. And the Old World animals shipped across proved indifferent to the poison: "no se sabe que de tal causa ningun caballo ni vaca, ni otro animal de quantos de España se truxeron, ni de los innumerables que dellos han proçedido, haya muerto: antes la han comido vacas, é los ratones cada dia" (p. 270).
The finished bread is described as a keeping ration and as merchandise. Baked, turned with wooden slats and dried a day or two in the sun, "queda muy buen pan ... é se sostiene en la mar", made half a finger thick for ordinary people and, for "personas prinçipales", as thin as a wafer and as white as paper, "y á esto delgado llaman xauxau". A load in Santo Domingo fetched "un ducado, quando es caro, é quando menos á medio pesso, y tambien llega algunas veçes á pesso de oro (que son quatroçientos é çinqüenta maravedis), é la carga es dos arrobas, que son çinqüenta libras de á diez é seys onças", and Oviedo calls it "buena granjería" because so much is consumed. It kept "un año é mas", travelled by sea through the islands and the coasts of Tierra Firme, "é aun hasta España lo he yo llevado é otros muchos", spoiling only if it got wet (p. 271).
The same page carries the loss. The expressed juice "es tan pésimo veneno, que con un solo y pequeño trago matará un elephante ó qualquier otro animal ó hombre viviente", yet boiled two or three times it was eaten as a broth, "como en un buen potaje y cordial"; boiled down by two thirds and left in the night air two or three days it turned sweet, and boiled and aired a second time it turned sour and served as vinegar. Then Oviedo writes, in 1535, of the island whose population had already collapsed: "estas experiençias pocos indios las saben ya haçer, porque los viejos son muertos, é porque los chrispstianos no lo han menester; porque para agro, hay tantas naranjas y limones en la Isla ... y assi se ha olvidado lo que en estos dos casos de dulçe é agro servia el çumo de la yuca" (p. 271). A body of applied chemistry is recorded in the act of disappearing, and the witness names both causes — the elders are dead, and the newcomers had no use for it.
Modern genetics locates the plant Oviedo was watching being processed. Olsen and Schaal's phylogeographic study of the nuclear G3pdh locus — 212 individuals, 28 haplotypes among 424 alleles — found haplotypes shared between cultivated cassava and wild populations only along the southern border of the Amazon basin, and concluded that "cassava was likely domesticated from wild M. esculenta populations along the southern border of the Amazon basin", from the wild subspecies flabellifolia and not, as had been proposed, from several progenitor species. The same paper states the crop's present weight: a staple for over 500 million people through the tropics, the primary source of carbohydrates in sub-Saharan Africa, and sixth among crops in world production.
The chain Oviedo described is not folklore, and the consequence of shortening it is measurable now. Konzo, "a permanent and clinically distinct upper motor neurone disease of abrupt onset" producing symmetrical, permanent and irreversible spastic paraparesis, follows chronic reliance on insufficiently processed cyanogenic cassava, the toxic metabolites named being cyanide, thiocyanate and cyanate. It falls on children above the age of three and on women of fertile age in sub-Saharan Africa, with prevalence "as high as 5% in certain rural areas"; a processing method discovered in 2005, the wetting method, has been used successfully in the Democratic Republic of the Congo to prevent outbreaks. The grater, the press and the fire were a public-health technology before the term existed, and populations that lose access to water or time for the full procedure pay for it in paralysis.
The crop's largest transfer was not a Spanish one, and this object does not claim it. Cassava reached tropical Africa from the New World through the Portuguese, who "are responsible of the initial diffusion of cassava around the world" and grew it around their trading ports, forts and castles in West Africa around 1558; approximately half of world production now comes from Africa, where it is cultivated in around 40 countries. Burkina Faso, the case study, received the crop only between the later nineteenth century and about 1912, by traders from Ghana and by missionaries — three and a half centuries after the Atlantic crossing — which is a useful check on any account that treats the exchange as a single sixteenth-century event.
Four limits are stated rather than implied. Only one colonial witness was opened for this object, Oviedo's chapter as printed in the 1851 Madrid edition, so nothing here settles who first described the plant in print or how other chroniclers rendered the same procedure. Oviedo was a crown officer and beneficiary of the conquest writing about a society his own side had destroyed, and his figure of speech about an elephant is a figure of speech, not an observation. The Taíno who devised the çibucan and the burén left no written account, so every word here about their technique reaches us through the man who watched it. And nothing read for this object connects cazabi to any named voyage or fleet contract: the claim that it went to sea, and to Spain, is Oviedo's own testimony about himself.