Extended Family Kinship
Although the extended family household as a cultural idea has been characterized in the majority of documented human history, it would be a mistake to believe that extended family households were characteristic of all historical societies or that all contemporary societies are dominated by the nuclear family. In truth, extended family households, even in societies where they were the ideal, may still have actually constituted only a minority of households; furthermore, the average amount of time the extended family spends under one roof is highly variable and often depends on factors such as economic need and the age of family members. Household formation is a cycle in which both nuclear and extended family households may appear and that these forms are not mutually exclusive. Contemporary Western models that herald the nuclear family household as ideal and minimize the importance of the extended family are relatively recent and have resulted from a number of factors, including: the Industrial Revolution, the associated rise of class influences in social networks, the increasing importance of individualism brought about by Western political change and education, the decline of kinship in defining social networks, and the replacement of government services for those traditionally associated with the family. Yet in the face of otherwise pervasive economic and social change toward Western cultural models, extended family households in non-Western societies have proved remarkably resilient.
Descent systems. Extended family ties that reach across households provide important social and economic advantages in terms of shared labor, socialization of children, and support for the elderly. In preindustrial societies, labor cooperation is often essential, and kinship is the primary means of defining the composition of groups. Extended family ties spread both risks and benefits— important especially in settings with scarce resources. In societies emphasizing descent as an organizing principle, extended family groups often form corporations of individuals who function in concert as a single social and economic unit. One traditional example is in contemporary hunter-gatherer societies, where resources are often uncertain, and individuals have minimal success in obtaining these resources. In these settings, highly elaborate rules, based on concepts of extended family, often govern the distribution of food and other resources. In this way, the success of an individual benefits the group.
Societies in which the extended family network is defined primarily through relationships between males are patrilineal. This type of descent system, where membership is passed from father to son, is most common cross-culturally. The Tiv of Nigeria, for example, live in extended polygynous family compounds consisting of the household head, several wives, and perhaps the household head's married brother, wives, and children. However, several such compounds linked by blood ties between males occupy a common contiguous territory and form a corporate economic unit more important than the household (Bohannan and Bohannan 1968). Patrilineal descent systems have dominated European and Chinese societies. Additional examples of these systems include the Juang of central India and Bedouin in Egypt (Stone 2001).
In matrilineal systems, membership in an extended family group is defined through women, and it is usually the son who moves to his wife's household. Matrilineal descent systems are most often found in sedentary agricultural societies where women perform the majority of agricultural tasks. Both the Hopi Indians of North America and the Trobriand Islanders off eastern New Guinea are prominent examples of cultures with matrilineal systems. Matrilineal societies also occur in small pockets in lacustrine central Africa, parts of northeast and southeast India, and south-central Vietnam (Parkin 1997). Matrilineal systems, not usually definable as matriarchies, nonetheless provide women with a degree of control over property and politics that is not found elsewhere.
In cognatic, or bilateral, descent systems, any combination of male and female kin may be used to define who constitutes the extended family network. This type of descent system is the most flexible in allowing individuals to define their own universe of extended family members. One example of this system is the Maori of New Zealand. Still other systems exist that do not consider blood relations as the basis of decent such as the Zumbagua of Ecuador, who believe kinship is established through food.
If the extended family network relationships can all be traced through a common known ancestor, this network may be said to constitute a lineage, particularly if the members function together as a single corporate unit. For example, all the members of a Tiv patrilineage can trace their relationship to a single known ancestor. If such links are not exactly known, or if they are based less in fact than in myth, the extended family network constitutes a clan.
Household composition. The importance of extended family ties is most easily seen in settings where family members share a common residence. Extended family households may be constituted by affinals, collaterals, or people of common descent. Extended family households based on common descent continue to exist in Western culture and remain prevalent throughout Europe, Asia, and the Americas. Descent-based households may be extended in several ways. The stem household form, made up of at least two generations of related nuclear families, is sometimes considered a class by itself. Stem family households are common in agricultural societies in which the elderly control the resources, and inheritance is based on primogeniture, meaning that all land is passed from father to first-born son. One popular theory, although widely contested, is that stem family households resulted from land scarcity and were an adaptation for keeping landholdings intact (Verdon 1979). An alternative view is that stem family households provide secure retirement environments for the elderly. In much of Asia, the stem family household still represents an important cultural norm (De Vos and Lee 1993: Foster 1978; Tsui 1989).
Households may also be extended either lineally (e.g., containing grandparents or grandchildren), collaterally (e.g., aunts or uncles, nephews, and nieces), or affinially (e.g., marriage). Collaterals are people of the same generation tied by kinship, such as joint families of India in which all brothers along with their wives and children share a common household. Affinial relationships are premised on marriage or cohabitation; examples include polygynous households and group marriages. Despite lack of acceptance in the Western world, such households are extremely common elsewhere, particularly in Africa and India.
Although there is no steadfast rule, contemporary extended family households based on common descent tend to show more lineal than collateral extension. Research indicates that African and Asian Americans are more likely to participate in lineally extended family households, with the former emphasizing the inclusion of children and the latter emphasizing inclusion of the elderly.