Kinship and descent

Kinship and descent is one of the major concepts of cultural anthropology. Cultures worldwide possess a wide range of systems of tracking kinship and descent. Anthropologists break these down into simple concepts which are common among many different cultures.

Descent groups
A descent group is a social group whose members claim common ancestry. A unilineal society (such as the Iroquois system) is one in which the descent of an individual is reckoned either from the mother's or the father's descent group. With matrilineal descent individuals belong to their mother's descent group (Not however through the mother directly. Usually descent is counted through the mothers brother, along with inheritance). With patrilineal descent, individuals belong to their father's descent group.

In a society which reckons descent bilineally, or bilaterally (such as the Eskimo system), descent from both father and mother is equally important.

Some societies reckon descent patrilineally for some purposes, and matrilineally for others. For instance, certain property and titles may be inherited through the male line, and others through the female line. This arrangement is sometimes called double descent.

Societies can also consider descent to be ambilineal (such as Hawaiian system) where offspring determine their lineage through the matrilineal line or the patrilineal line.

Lineages, clans, phratries and moieties
A lineage is a descent group that can demonstrate their common descent from an apical ancestor. Lineages can be matrilineal or patrilineal, depending on whether they are traced through mothers or fathers, respectively. Whether matrilineal or patrilineal descent is considered most significant differs from culture to culture.

A clan is a descent group that claims common descent from an apical ancestor (but often cannot demonstrate it, or "stipulated descent"). If a clan's apical ancestor is nonhuman, it is called a totem. Examples of clans are Scottish, Irish, Tlingit, Chechen, Chinese and Japanese clans.

A phratry is a descent group containing at least two clans which have a supposed common ancestor.

If a society is divided into exactly two descent groups, each is called a moiety, after the French word for half.

The nuclear family
The Western model of a nuclear family consists of a couple and its children. The nuclear family is ego-centered and impermanent, while descent groups are permanent (lasting beyond the lifespans of individual constituents) and reckoned according to a single ancestor.

Kinship calculation is any systemic method for reckoning kin relations. Kinship terminologies are native taxonomies, not developed by anthropologists.

Beanpole family is a term used to describe expansions of the number of living generations within a family unit, but each generation has relatively few members in it.

Legal ramifications
Kinship and descent have a number of legal ramifications, which vary widely between legal and social structures.

Most human groups share a taboo against incest; relatives are forbidden from marriage but the rules tend to vary widely once one moves beyond the nuclear family. At common law, the prohibitions are typically phrased in terms of "degrees of consanguinity."

More importantly, kinship and descent enters the legal system by virtue of intestacy, the laws that at common law determine who inherits the estates of the dead in the absence of a will. In civil law countries, the doctrine of legitime plays a similar role, and makes the lineal descendants of the dead person forced heirs. Rules of kinship and descent have important public aspects, especially under monarchies, where they determine the order of succession, the Heir Apparent and the Heir Presumptive.

Kinship systems
The six major kinship systems identified by Louis Henry Morgan in his 1871 work Systems of Consanguinity and Affinity of the Human Family are:
 * Crow kinship (an expansion of Bifurcate Merging)
 * Eskimo kinship (also referred to as Lineal kinship)
 * Hawaiian kinship (also referred to as the Generational system)
 * Iroquois kinship (also known as Bifurcate merging)
 * Omaha kinship (also an expansion of Bifurcate Merging)
 * Sudanese kinship (also referred to as the Descriptive system)