Many societies construct kinship groupings, roles, and relationships by tracing descent exclusively through the male - patrilineal - or female - matrilineal - line. The resulting units are called unilineal descent groups, either patrilineages or matrilineages according to the prevailing descent rule. Unilineal kinship institutions occur at over twice the incidence of cognatic ones among the world's cultures. In many societies, unilineal descent groups assume important corporate functions such as land ownership, political representation and mutual aid and support.
Patrilineal societies are much more common than matrilineal ones, occurring at roughly twice the incidence and accounting for 60% of all unilineal systems and 40% descent systems (unilineal and cognatic) thoughout the world. They may be familiar to you from the Bible, (the "tribes" of Israel were patrilineages) and ancient Greek and Roman family organization. Matrilineal systems are less frequent but are still ethnographically important. The powerful West African Ashanti kingdom developed within a matrilineal society. Accordingly, the heir to the throne is not the king's (Asantehene's) own child but his sister's son. Early British emissaries to Ashanti learned about this family system the hard way. They supported several of the Asantehene's sons to be educated in England only to realize that the allies they had so carefully cultivated were not in line to assume the throne.
A third unilineal form, dual descent, involves the presence of significant patrilineal and matrilineal groupings in single society. Their occurance is relatively rare.
Incidence of Descent Rules among Unilineal Societies
Source: Murdock 1949:59.