Until the later 20th century, clans were a phenomenon of great interest to anthropologists (anthropology), but since then they have generally become less important in analyses of cultural organization. From a functional perspective, clans help to unify groups by cross-cutting other forms of social organization, such as the settlement, postmarital residence patterns, or age sets (age set). Allied clans generally have reciprocal relations, providing each other with mutual support and defense and with emotionally or financially taxing services such as funerals. Some clans express their unity in terms of the possession of a common emblem, which may represent the ancestral being or common origin of the members and, as such, is often an object of reverence.