The “revolution of domestication,” beginning around 11,500 years ago, involved both plants and animals. People living in more favored environments were able to combine farming with animal husbandry and on this economic foundation generated powerful and impressive civilizations with substantial populations. But on the arid margins of agricultural lands, where productive farming was difficult or impossible, an alternative kind of food-producing economy emerged around 4000 B.C.E., focused on the raising of livestock. Peoples practicing such an economy learned to use the milk, blood, wool, hides, and meat of their animals to occupy lands that could not support agricultural societies. Some of those animals also provided new baggage and transportation possibilities. Horses, camels, goats, sheep, cattle, yaks, and reindeer were the primary animals that separately, or in some combination, enabled the construction of pastoral or herding societies. Such societies took shape in the vast grasslands of inner Eurasia and sub-Saharan Africa, in the Arabian and Saharan deserts, in the subarctic regions of the Northern Hemisphere, and in the high plateau of Tibet. Pastoralism emerged only in the Afro-Eurasian world, for in the Americas the absence of large animals that could be domesticated precluded a herding economy. But where such animals existed, their domestication shaped unique societies adapted to diverse environments.