Chuño: the freeze-dried potato of the Collao in the first printed accounts, and its trade to Potosi
The potato entered print in 1553 not as a curiosity but as a food security system. Cieza describes the Collao drying papas in the sun and keeping them from one harvest to the next as chuño, the reserve that stands between an unirrigated highland and famine - and reports that Spaniards grew rich carrying it to sell at the mines of Potosi. Acosta confirms the trade in 1590 and adds the harvest failures. The plant Europe later grew came mostly from elsewhere in the Andes.
Why this wins its question: The potato's usual English story starts in Europe, with Raleigh or with the famine, and treats the Andean original as prehistory. The two earliest printed accounts say something more specific and more useful: that the storable form was the point, that it was what allowed an unirrigated highland to survive a failed year, and that within twenty years of the conquest it had become a bulk commodity feeding the largest silver mine in the world, on which Spaniards - not the growers - made fortunes. This object quotes both chapters, keeps the profit and the silence about the growers' side on the record together, and states that the modern European crop descends mostly from a different Andean stock.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
Cieza de Leon's first part of the Chronicle of Peru, printed at Seville in 1553, states in the chapter on the Collao that the chief sustenance of its people is papas, roots he compares to truffles of the earth; that they dry them in the sun and keep them from one harvest to the next; and that the dried potato is called chuño among them and is held in great price.
He gives the reason it is prized, and it is a hydrological one: the Collao has not the water or the channels that much of the rest of the kingdom has for watering its fields, so that when the natural water fails for sowing the people suffer want and hardship unless they have this sustenance of dried potatoes in store.
The same passage reports a commercial fact that is rarely quoted with it: many Spaniards grew rich, and went back to Spain prosperous, by carrying nothing but this chuño to sell at the mines of Potosi. Cieza states it as common knowledge of the country without giving figures, which is why it carries a lower confidence here than his description of the food itself.
He names the rest of the highland complex in the same place - oca, and the seed called quinua, small as rice - and states the risk plainly: in an abundant year all the dwellers of that Collao live content and without want, but if it is barren and short of water they pass the greatest want.
Acosta's Natural and moral history of the Indies, Seville 1590, gives the same complex a chapter of its own in the fourth book, on the yucas, cazabi, papas, chuño and rice. It states that in the high country of Peru and the provinces of the Collao the weather is so cold and dry that neither wheat nor maize will grow, and that in their place the Indians use papas, which they gather, dry well in the sun, and break to make what they call chuño.
Acosta confirms the trade Cieza had reported thirty-seven years earlier, and in the same terms: chuño keeps many days, serves them as bread, and there is in that kingdom a great trade in it for the mines of Potosi. He adds the fresh uses - papas boiled or roasted, and a stew called locro made from a milder kind that also grows in warm places.
Acosta also records why the reserve was needed. These roots, he writes, are all the bread of that land, and when the year is good for them the people are content, because in many years they are blighted and frozen in the ground itself, so cold and harsh is that region - a crop that fails often enough that a storable form of it is not a convenience but the condition of living there.
Neither witness is disinterested and the profit they record is not the growers'. Cieza came to Peru with the conquest and writes as a settler; Acosta was a Jesuit provincial writing to justify the mission. Both name the Spaniards who grew rich on the chuño trade to Potosi; neither says what the households of the Collao received for it, and no source read here documents that side of the exchange.
The potato that Europe eventually grew is not simply the one these chapters describe. Work on the cytoplasmic genomes of European potatoes reports that the first introduction into Europe is thought to have been Solanum tuberosum ssp. andigena, that Chilean forms of ssp. tuberosum introduced later became the ancestors of modern cultivars, and that the T-type cytoplasm predominates in European potatoes because most varieties descend maternally from Rough Purple Chili and a few other clones of ssp. tuberosum.
The date and route by which the potato reached Spain are not asserted here. No source opened for this object documents them, and the sixteenth-century chapters read here describe the plant in the Andes and its market at Potosi, not its passage to Europe.