How the Potato Changed the World's History

Social Research, Spring, 1999 by William H. Mcneill

My title is not as absurd at it sounds, even though historians have only recently begun to take notice of how the spread of potatoes and other American food crops to the Old World--potatoes and maize in particular, but also tomatoes, peanuts and half a dozen other foods we now take for granted--changed human lives, often in quite drastic ways. Nor is the idea that potatoes made a difference for Europe a new one. In the early nineteenth century, for example, Ludwig Feuerbach and other radicals believed that "potato blood" was weakening the German people and delaying the revolution they looked forward to, while a long list of social improvers argued the contrary, beginning as early as 1664 with an obscure pamphlet written by one John Forster, whose title speaks for itself: England's Happiness Increased: A sure and easy remedy against all succeeding dear years by a plantation of the roots called potatoes (London, 1664).

Today, potatoes are a valued and important crop in China as well as in Europe and North America, and remain the staple food of Andean farmers in the South American altiplano. But only twice can one say that potatoes made a critical difference for world history: initially in the altiplano, where potatoes provided the principal energy source for the Inca Empire, its predecessors and its Spanish successor; and then subsequently in northern Europe, where potatoes, by feeding rapidly growing populations, permitted a handful of European nations to assert dominion over most of the world between 1750 and 1950. Elsewhere, potatoes were only a supplement to other foods, and had comparatively minor impact on human affairs, so I will confine my remarks to the potato's special role in the altiplano and in northern Europe.

The plant botanists call Solanum tuberosum was native to the Andes and still grows wild there along with a large number of cultivated varieties--some of which we would not easily recognize as close kin to the potatoes we buy in our grocery stores. Exactly when such plants were first cultivated is uncertain: perhaps as early as 3000 B.C.E. and almost certainly before 2000 B.C.E.. Deliberate selection for desired characteristics altered wild ancestral varieties long before modern plant breeders did the same for the potatoes in use today. But some enduring features explain why this particular crop played a critical role in sustaining a succession of imperial states in the forbidding climate of the altiplano and did the same again for a handful of states in northern Europe a few centuries after Spanish conquistadors took over the Inca empire in 1532-33.

First of all, potatoes yield abundantly, and adapt readily to diverse climates so long as the weather remains cool and moist enough for the plants to gather sufficient water from the soil to form the starchy tubers. On the other hand, potatoes do not keep very well in storage. After a period of dormancy, even a little warmth provokes the eyes (i.e., buds) to use the energy resources stored in the tuber to sustain rapid growth of new shoots; and they start to grow regardless of whether they are lying where nature put them in the ground or are piled into storage cellars or bins. Moreover, during the period of dormancy, potatoes are vulnerable to moulds that feed on the stored tubers just as readily as people do, quickly turning them rotten. Storage for more than a few months is therefore impractical, even with modern temperature controls.

By comparison, harvested grain is very dry and cannot sprout or mould without exposure to additional moisture. Grain can therefore be stored for several years without much risk of rotting. Keeping mice and rats away required clay jars or similarly fight containers, which is why early pottery-making and grain farming were so closely associated. Reliable storage methods, in turn, allowed tax and rent collectors of the Old World to gather sufficient grain into storehouses to sustain urban civilizations across millennia, starting about 3000 B.C.E.. In the altiplano, however, grain did not flourish nearly as well as potatoes, though the Incas did raise maize and another very nutritious seed crop, quinoa, in some protected valleys. But in the high plains around Lake Titicaca, potatoes alone were capable of maturing, and they flourished abundantly there on artificially raised fields built out into the marshy margins of the lake.

Mere abundance was not enough to make moist, perishable tubers capable of maintaining civilized society at 12,500 feet above sea level. Safe and reliable storage was also required. This was possible owing to the fact that even in those tropical latitudes freezing temperatures set in at night through much of the year. That climatic peculiarity allowed farmers of the high Andes to resort to a technique for preservation that is very familiar to us these days--frozen food--even without artificial refrigeration. Merely by exposing tubers to the night air, they converted potatoes into what the Incas called by a term the Spaniards rendered as chuno; and when stored in sealed, permanently-frozen underground storehouses, chuno could be kept for several years with no loss of nutritional value.