Roots and Tubers

Potatoes, sweet potatoes, yams, cassava— these roots and tubers are staple foods for billions of people. They are subterranean organs in which plants store starch, large molecular aggregates of the sugars they create during photosynthesis. They are therefore a concentrated and long-lived package of nourishment for us as well. Some anthropologists theorize that roots and tubers may have helped fuel human evolution, when the climate of the African savanna cooled about 2 million years ago and fruits became scarce. Because tubers were plentiful and far more nutritious when cooked—raw starch granules resist our digestive enzymes, while gelated starch does not—they may have offered a significant advantage to early humans who learned to dig for them and roast them in the embers of a fire.