Sheep and goats were among the earliest animals to be domesticated, following only dogs, which were most useful to hunter-gatherer humans. In fact, sheep have been domesticated so long, they are unable to return to a feral, or wild, state. Domestic sheep require human involvement for their survival. Like several other important early agricultural milestones, sheep domestication occurred in Mesopotamia, the fertile crescent, also known as the Cradle of Civilization. Wild sheep were fine candidates for domestication because they didn’t exhibit aggression, their size was ideal for human management, and they had high reproduction rates, ensuring herd growth and health.