A glance at the topographical and meteorological characteristics of the Iberian Peninsula is the first prerequisite of the study of Spanish economic history. The differentiation of social and economic phenomena of Spain arising from isolation and separatism, accentuated by the varied and shifting patterns of political control, present serious obstacles to a comprehensive survey of agrarian conditions. Information on the study of the character, efficiency, and well-being of agricultural workers topics appears as byproducts of work primarily concerned with medieval property rights, land tenure, and legal institutions. The various arrangements for appropriating land were in large part products of Spain's unique role in making Europe safe for Christianity. An important chapter in Spanish agrarian history is the relation between agriculture and grazing. The merino sheep, Spain's great contribution to international trade and to the pastoral industry of the world, were probably introduced from Africa in the twelfth century.