Around the time that our ancestors domesticated animals, they also began to cultivate a number of grasses, plants that grow in extensive stands and produce large numbers of nutritious seeds. This was the beginning of agriculture. With the arrival of domesticated barley and wheat, rice and maize, nomadic peoples settled down to farm the land and produce food, populations boomed—and most people ate very little meat. Grain crops are simply a far more efficient form of nourishment than animals grazing on the same land, so meat became relatively expensive, a luxury reserved for the rulers. From the prehistoric invention of agriculture to the Industrial Revolution, the great majority of people on the planet lived on cereal gruels and breads. Beginning with Europe and the Americas in the 19th century, industrialization has generally made meat less expensive and more widely available thanks to the development of managed pastures and formulated feeds, the intensive breeding of animals for efficient meat production, and improved transportation from farms to cities. But in less developed parts of the world, meat is still a luxury reserved for the wealthy few.