The Iranian plateau is an ideal area for investigating the relationship be? tween ecological and sociological factors because of its stark aridity, on the one hand, and its historical role as a meeting place of ethnic and cultural movements on the other. The part of the plateau which forms the southeast corner of Persia is particularly interesting from this point of view. Over an area of some 200,000 square kilometers the great majority of the population, which numbers about half a million and includes both peasants and nomads, call themselves Baluch. Most, but not all of them, speak a dialect of Baluchi as their native tongue, and practically all adults speak it as a lingua franca. However, their political and social organization shows important variations, and there are striking geographical variations in the country they inhabit. It is unusual to find such wide variations among people who consider themselves one society. This paper shows how the variations in political and social organization in the area may be related to variations in human ecology. I wish to demonstrate that in this area of Persia, where political leadership relies on an income from settled agriculture, there is a definite social differentiation into classes and cognatic values are given to kin relationships, whereas leadership which relies primarily on nomadic pastoralism works through a structure of agnatic kin relationships without class differentiation.