The rapid spread of Islam into three continents in the seventh and eighth centuries was followed by the diffusion of an equally remarkable but less well documented agricultural revolution. Originating mainly in India, where heat, moisture and available crops all favored its development and where it had been practiced for some centuries before the rise of Islam, the new agriculture was carried by the Arabs or those they conquered into lands which, because they were colder and drier, were much less hospitable to it and where it could be introduced only with difficulty. It appeared first in the eastern reaches of the early-Islamic world—in parts of Persia, Mesopotamia and perhaps Arabia Felix—which had close contacts with India and where a few components of the revolution were already in place in the century before the rise of Islam. By the end of the eleventh century it had been transmitted across the length and breadth of the Islamic world and had altered, often radically, the economies of many regions: Transoxania, Persia, Mesopotamia, the Levant, Egypt, the Maghrib, Spain, Sicily, the savannah lands on either side of the Sahara, parts of West Africa and the coastlands of East Africa. It had very far-reaching consequences, affecting not only agricultural production and incomes but also population levels, urban growth, the distribution of the labor force, linked industries, cooking and diet, clothing, and other spheres of life too numerous and too elusive to be investigated here.