Hunter-gatherer groups migrated to rich and diversified landscapes where they settled and participated in agriculture. Agriculture transformed plants and animals through selective planting and breeding, and neighboring communities exchanged agricultural knowledge. The peoples of Southwest Asia invented a mixed farming method involving grain production and animal domestication. This style of farming spread to Europe and Africa, and civilization began to center on towns near farms. In Northern China, agriculture was dominated by rice cultivation, while sub-Saharan Africans cultivated sorghum and millet and herded cattle. In the Americas, people produced maize, beans, and squash (in Mexico); sunflowers and gourds (in the eastern US); and root crops such as manioc, potatoes, sweet potatoes, and quinoa (in South America). South American peoples domesticated llamas, alpacas, and guinea pigs. In comparison to Eurasia, however, the Americas cultivated less land and had fewer domesticable species. In addition, Eurasia had the advantage of more temperate climates.

Although humans’ success in agriculture brought positive changes, it also brought new challenges, such as vulnerability to infection, crop failure, famine, and organized warfare. Additionally, the emergence of settled communities transformed social relationships. The instabilities and challenges of expanding and tightening webs provoked the technological, religious, intellectual, political, economic, and institutional changes that accompanied the rise of civilization and urban life.