THE NUER OF THE SOUTHERN SUDAN 287
sections X and Y; major lineages D and E correspond to secondary section X1 and X2; major lineages F and G correspond to secondary sections Y1 and Y2; and minor lineages J and K correspond to tertiary sections Z1 and Z2.
We speak of a clan which is dominant in a tribe as the aristocratic clan, although, except on the periphery of Nuer expansion eastwards, its predominance gives prestige rather than privilege. Its members are in a minority—often a very small minority—in the tribe. Not all members of the aristocratic clan live in the tribe where it is dominant, but many are also found in other tribes. Not all clans are associated with a tribe in this manner. A man is only an aristocrat in the one tribe in which his clan is dominant. If he lives in another tribe, he is not an aristocrat there.
There is consequently in every tribe some social differentiation. There are aristocrats, Nuer of other clans, and Dinka, but these strata are not classes and the second and third are properly to be regarded as categories rather than as groups. The Dinka who have been absorbed into Nuer society have been for the most part incorporated into their kinship system by adoption and marriage, and conquest has not led to the development of classes or castes. This is, perhaps, to be attributed, in part at any rate, to the fact that the Dinka, like the Nuer, are chiefly pastoralists and that in other respects their ways of life are very similar.
Without presenting all the evidence and without making every qualification, we attempt an explanation of why Nuer clans, especially the dominant clans, are segmented into lineages to a far greater degree than is usual among African peoples. In our view, they are segmented because the political structure to which they correspond is ^segmented in the way we have described. Social obligations among the Nuer are expressed chiefly in a kinship idiom and the interrelations of local communities within a tribe are defined in terms of agnatic relationship. Therefore, as the tribe segments the clan segments with it and the point of separation between the tribal sections becomes the point of divergence in the clan structure of the lineages associated with each section. For, as we have seen, clans and their lineages are not distinct corporate groups, but are embodied in local communities, through which they function structurally. Such being the case, it is not surprising that they take the form of the State which gives them corporate substance.