Segmentary lineage systems are a form of decentralized and egalitarian social organization consisting of nested groups vested with the responsibility for security, defense, and welfare. Lineage systems are characterized by groups defined by descent from a common ancestor. Small groups trace their descent to close ancestors, whereas large groups (encompassing many small groups) trace their descent to distant ancestors. For groups to be discrete and not overlapping, descent is traced unilineally—through one line, either male or female. Patrilineages trace through the male line and are dominated by male and female descendants of the common male ancestor; matrilineages trace through the female line and are dominated by male and female descendants of the common female ancestor. In patrilineal systems, only males pass on group membership to their children; women’s children are members of their fathers’ groups. Conversely, in matrilineal systems, only females pass on group membership to their children; men’s children are members of their mothers’ groups.
Lineage systems are segmentary in that each group takes the same form as every other group, whether large or small, with each segment being like every other. These segments are organized in relation to one another into a balanced opposition. This organization is based on the general principle that genealogically closer groups unite in opposition to more distant groups and on the contingent nature of these groups by which they are activated only in situations of opposition to groups of structural equivalence and equal size. For example, if two men who are members of minor lineages in the same tribal section fight, only the members of each minor lineage are involved, but if members of two different tribal sections fight, all members of each section, regardless of minor lineage membership, are involved and, if mobilized, are acting as section members.
Segmentary lineage systems are important because in many tribal societies lineage groups based on descent through the male line are vested with important economic and political responsibilities. In segmentary lineage systems, patrilineages commonly have collective ownership of, or particular claims on, important resources such as land and water sources. In general, lineages are responsible for security, providing the defense force and undertaking collective responsibility for gaining restitution or taking vengeance for losses and injuries. The original and most famous description of these systems, The Nuer, described a pastoral tribal people living in the southern Sudan. Edward Evan Evans-Pritchard recounted the correspondence between the lineage system and the territorial system that made possible their functioning as a decentralized, egalitarian, and expansionist political system. These systems are widespread in Africa (Somali, Libyan Bedouin) and in the Middle East (Turkmen, Arabian Bedouin, Baluch).
Segmentary lineage systems are best understood as means of defense and social control. The balanced opposition serves as a deterrent to aggressive adventurism. Collective responsibility of group members for each other guarantees that no individual or small group is a free target. Loyalty to one’s lineage is not so much a sentimental attachment to blood kin as it is a hardheaded recognition of who one can count on when one gets into trouble.
Segmentary lineage systems are found where tribal political organization is possible. These systems provide security for life and property where important property, such as livestock and wells, need constant protection. They are also found where nonterritorial means of relating people are useful such as among pastoral nomads, where people are frequently moving around and mixing. Under strong states, segmentary lineage systems are suppressed as competing powers.
- Evans-Pritchard, E. E. (1940). The Nuer: A description of the modes of livelihood and political institutions of a Nilotic people. Oxford, UK: Clarendon.
- Evans-Pritchard, E. E. (1949). The Sanusi of Cyrenaica. Oxford, UK: Clarendon.
- Irons, W. (1975). The Yomut Turkmen: A study of social organization among a Central Asian Turkic-speaking population (Anthropology Paper No. 58). Ann Arbor: University Michigan, Museum of Anthropology.
- Lancaster, W. (1997). The Rwala Bedouin today (2nd ed.). Prospect Heights, IL: Waveland.
- Lewis, I. M. (1961). A pastoral democracy: A study of pastoralism and politics among the Northern Somali of the Horn ofAfrica. Oxford, UK: Oxford University Press.
- Salzman, P. C. (2000). Black tents of Baluchistan. Washington, DC: Smithsonian Institution.
- Salzman, P. C. (2004). Pastoralists: Equality, hierarchy, and the state. Boulder, CO: Westview.