Descent
The rules a society uses to trace kinship, inheritance, and group membership across generations. Bilateral descent traces kinship roughly equally through both parents, as in most English-speaking societies; unilineal descent (matrilineal or patrilineal) traces membership through only one parent's line, producing discrete, permanent corporate groups — the basis of the segmentary lineage systems British structural-functionalists like Evans-Pritchard documented in stateless societies such as the Nuer.