A number of writers have noted that for East Africa, age organization and lineage organization are structural alternatives. More precisely, Southall (1970) has argued that the full and dominant development of age organization is incompatible with that of a segmentary lineage structure. Forde (1971) has similarly concluded that the two may be alternatives, and that selection between them may be partly dependent on ecological factors. However, I would like to contend that to write of the elaboration, or non-elaboration, of age structures and descent groups or of a conflict of allegiances, may well be a sterile exercise if it is unrelated to an analysis of the mode of livelihood of the people concerned. Furthermore, in light of the modern view of social structure as the outcome, at any point in time, of continuous processes of destructuring and restructuring, the ceaseless turnover of the membership of society, which age structures attempt to reduce to order, can be seen as one of the major sources of these processes, as Bottomore has recently argued (1975). Thus a source of structural stress, and hence ultimately of change, more important, I would argue, than the conflict between age and descent, is that between the generations.