The Potato Leaves the Andes
1Long before 1492, peoples of the Andes Mountains, in what are now Peru and Bolivia, turned a wild plant into the potato. Over thousands of years, farmers there bred hundreds of kinds, each suited to a different height, soil or climate. Potatoes grew high on cold slopes where maize could not ripen. Andean farmers also made chuño: they left potatoes out to freeze on cold nights, pressed out the water and dried them in the sun. Chuño could be stored for years. Quechua and Aymara farmers in the Andes still grow many kinds of potatoes and make chuño today.
2The exchange that followed Columbus's voyages ran in both directions. In the Andes, Spanish colonists introduced wheat, barley, cattle, sheep and horses. Diseases came too. Smallpox spread through the Inca Empire in the 1520s, even before Spanish soldiers arrived, and killed many people, probably including the ruler Huayna Capac. After the Spanish conquered the Inca in the 1530s, they found a huge silver deposit at Potosí in 1545 and sent thousands of Indigenous men, many of them forced, to work in its mines.
3Potatoes crossed the Atlantic in the 1500s. By the 1570s, a hospital in Seville, Spain, was buying them for its patients. Many European farmers were slow to plant them. The plant looked strange, it grew from pieces of potato rather than from seed, and some people believed it caused illness. Over the next two centuries, however, potatoes spread across Europe.
4Potatoes grew well in cool, damp places and in poor soil, and a field of potatoes could feed more people than a field of the same size planted with wheat or rye. Populations in Europe, Asia and Africa grew quickly between 1700 and 1900, and one study estimated that the potato explains about a quarter of that growth. Yet depending on one crop was risky. In Ireland, many poor families ate little else. When a plant disease called blight, which had crossed the Atlantic from the Americas, destroyed the potato crops beginning in 1845, about one million people in Ireland died and more than a million left the country.