Final answer:
A special group of relatives descended from a single ancestor is called a lineage. Unilineal descent traces kinship through one gender line, forming clans of related lineages.
Step-by-step explanation:
A special group of relatives who are all descended from a single ancestor is called a lineage. In social studies, particularly anthropology, unilineal descent traces an individual's kinship through a single gendered line as a social rule for all families within a society. This could be either a patrilineal descent (through the male line) or a matrilineal descent (through the female line). Lineages that are believed to be closely related are sometimes organized into clans, which are larger groups denoting a symbolic kinship. These lineages and clans display the interconnected nature of kinship bonds within societies, which play a role in the structure and governance of communities, as well as in the resolution of disputes and in maintaining social cohesion.