People in both North America and South America ate lots of sweet potatoes. That’s because sweet potatoes are very good for you. They have lots of calcium, potassium, Vitamin A, and Vitamin C, and your body needs all of those things. Plus, sweet potatoes taste good. They are very sweet, which helps to give you energy. Sweet potatoes are distantly related to morning glory flowers, and also to white potatoes.
Sweet potatoes are a kind of vine, with white flowers. The part you eat is the root of the vine plant. People first ate sweet potatoes by gathering them in the wild, where they grew naturally, which was in Central America and the warmest parts of South America.
But sweet potatoes were so useful and so good that by about 3000 BC people had learned to grow them on purpose, and soon they shared that knowledge with their neighbors, and so after a while people were growing sweet potatoes all over South and North America, wherever it was warm enough for the plant to grow.
Sometime around 1000 AD, sweet potatoes also reached New Zealand and the Philippines, possibly by floating in the ocean, or because Pacific islanders sailed to Peru and got the sweet potatoes there.
When European people first came to live in North and South America, they also learned to eat a lot of sweet potatoes. Sweet potatoes were a main food of European people living in America in the 1500s, 1600s, and 1700s AD. Spanish traders quickly brought sweet potatoes to sell in Africa, India and China, and by the 1600s many people in China ate sweet potatoes as their main food instead of rice.
When African people came to North America, they called sweet potatoes “yams”. That’s because back home in Africa, they had eaten a food that was a lot like sweet potatoes, which in Africa was called “nyami” or “anyinam“. They aren’t really the same plant, but they look and taste a lot alike, so the African people called sweet potatoes “yams.” African-American people cooked sweet potatoes the way they had cooked yams back home, and ate a lot of them.
In the United States, people cooked sweet potatoes by just putting them in the coals from the fire, so they would roast and be like baked potatoes. Or they cut sweet potatoes into chunks and boiled them, and then mashed them with eggs to bake into sweet potato pie. But in China, people made sweet potatoes into noodles, or into stew with soy milk.
Bread Comes to Life: A Garden of Wheat and a Loaf to Eat, by George Levenson (2004). From wheat to bread, lavishly illustrated, for kids.
Ancient Agriculture: From Foraging to Farming, by Michael and Mary Woods (2000). For middle schoolers, with plenty of information about how farming got started, and how it worked.