tribe [Lat., tribus : the tripartite division of Romans into Latins, Sabines, and Etruscans], a social group bound by common ancestry and ties of consanguinity and affinity; a common language and territory; and characterized by a political and economic organization intermediate between small, family-based bands, and larger chiefdoms. Some anthropologists believe that tribes developed when more stable and increased economic productivity, brought on by the domestication of plants and animals, allowed more people to live together in a smaller area. A tribe may consist of several villages, which may be cross-cut by clans, age grade associations, and secret societies; each of these cross-cutting institutions may, at different times and in different ways, perform economic, political, legal, and religious functions. Tribes are popularly believed to be close-knit and parochial, but some anthropologists now argue that they are flexibly defined communities of convenience. They have observed that there has been as much marriage between tribes as within, that members of many tribes may speak the same language and that members of any one tribe may speak different languages, and finally that all members of a given tribe rarely—if ever—unite in any important political or economic activity. Anthropologists have noted that every known tribe has been in contact with states, and suggest that tribal institutions may be adaptations to the greater state power, or direct consequences of the activities of states.