xxii AFRICAN POLITICAL SYSTEMS
Besides the development of political office, though not independent of it, we have to take account of the various forms of political inequality. The simplest example of this is afforded by differentiation on the basis of sex and age; men usually take far more part than women, not only in war, but also in maintaining internal order, and older men, as a rule, have more authority than younger ones. Gerontocracy—rule by elders—is a form of political organization that is found in some parts of Africa. In some tribes of East Africa it is systematized by means of a definite structure of age-sets and age-grades. Where a society is under a chief or king, we may find an element of gerontocracy combined with the monarchical principle.
The Banyankole described in this book are an example of a division into politically unequal classes. The political power rests with the pastoral Bahima, who thus constitute a ruling class, while the agricultural Bairu are in an inferior position. In this instance and in a number of others there is good reason to believe that this differentiation into politically superior and inferior classes is the result of conquest, but it is going far beyond the evidence to assume that political inequality has in all instances arisen in this way. In the Banyankole and similar tribes, the political inequality is associated with other differences and the class structure is maintained by the difference in the mode of life of overlords and subjects and by the absence of intermarriage.
Thus in the comparative study of political systems we are concerned with certain special aspects of a total social structure, meaning by that term both the grouping together of individuals into territorial or lineage groups and also the differentiation of individuals by their social role either as individuals or on the basis of sex and age or by distinctions of social classes.
Social structure is not to be thought of as static, but as a condition of equilibrium that only persists by being continually renewed, like the chemical-physiological homostasis of a living organism. Events occur which disturb the equilibrium in some way, and a social reaction follows which tends to restore it. Sometimes a system may persist relatively unchanged for some length of time; after each disturbance the reaction restores it to very much what it was before. But at other times a disturbance of equilibrium may be such that it and the reaction which follows result in a modification of the system; a new equilibrium is reached which differs