TRIBE. A tribe is defined by Dr. Rivers as "a social group of a simple kind, the members of which speak a common dialect, have a single government, and act together for such common pur poses as warfare." In this definition it is necessary to understand by single government a political unity of a very simple kind, which may not imply the existence of any obvious mechanism of government, such as an hereditary monarchy or an elected coun cil, with which we are familiar amongst civilized peoples.
Although it is usual to regard primitive peoples as always or ganized in definite tribes (Carveth Read, The Origin of Man and his Superstitions, 1925), the tribe as a definite group is often en tirely lacking. In the case of pastoral peoples, definite groups with a political function, transcending families and clans, are likely to occur, but a settled population needs no such unification, unless the special demands of industry or the need for united action in warfare necessitate central control or the delimitation of groups. Thus it is often difficult in Melanesia to find any division of the people into distinct political units. One district usually shades into another politically, unless there is established enmity between the groups; and the names of groups, which might be thought to be tribal names, are found to be of indefinite ex tension. In these cases the social and political organization is com
prised in the family, clan and local relations ; the political soli darity of any given district depends on the sum-total of family, clan, local and personal relationships in that district (W. E. Arm strong, Rossel Island, 1928). There is tribal organization but there are no distinct tribes. In other places, however, in which social organization is of the same general kind, but in which conditions, such as isolation on a small island, or historical circumstances, have unified a district, on account of economic or other conditions, we can speak of definite tribes. In so far as the political unity of such a district becomes dependent on locality, rather than on kin ship and other relationships between the members of the district, the tribe passes into a simple form of state. For Indian tribes, see NORTH AMERICA, Ethnology.