Kinship is an adaptive mechanism. As a sociocultural construction, it is defined differently across cultures to adapt to the specific needs of a society. While most of us think of kinship as a biological relationship, it is, in fact, a relationship defined by culture. Historically, anthropology approached the study of kinship as a collection of terms and relationships. Lewis Henry Morgan did early research on the diversity of kinship across societies. Bronislaw Malinowski and A. R. Radcliffe-Brown revealed kinship’s institutional nature and how it connects to other aspects of social life, such as politics, economics, and subsistence. Today, anthropologists view kinship as one of the foundational social structures and institutions within a society. It defines the way an individual (EGO) fits within a larger kindred (depicted by terms of reference) and the rights and obligations that EGO has to these individuals (depicted by terms of address).
Embedded within the larger kinship structure is the family, those believed to be related to each other and who have distinct rights and responsibilities to the family unit. Some families live together with mutual goals while others are disperse, claiming ancestral kinship ties. Families also include individuals who share ties of descent (consanguineal ties) and ties of marriage (affinal ties). A household is a group of individuals who live within the same residence and share socioeconomic needs. This may or may not include more than one family. There are various types of families across cultures, including the nuclear family, extended family, and blended family. Many families also include fictive kin, individuals who are included within the intimate family and perceived to have relationships as close as those of blood or marriage. Godparenthood, called compadrazgo in Latin American, is an example of fictive kin.
Kinship is graphically depicted by means of a kinship chart, which shows the kindred connected by consanguineal and affinal ties. All kinship charts use a point of reference referred to as EGO, the individual whose relationships are traced on the chart. There are three major types of kinship structure: lineal kinship, which highlights the nuclear family; bifurcate merging kinship, which distinguishes between parallel and cross cousins; and generational kinship, which greatly expands the family of orientation to include all kindred within the same generation. Ties of descent, whether unilineal, ambilineal, or bilateral, drive connections within a kinship chart. In some families, descent (and inheritance) is traced through only one of EGO’s parents (unilineal or ambilineal), and in others descent is traced through both parental lines (bilateral).
EGO’s family of orientation is ideally created through a marriage (affinal tie), but what constitutes marriage varies greatly across cultures. In short, marriage is best defined as the formation of a new, socially sanctioned family. Some societies practice monogamy, the marriage of only two adults at a time. Where individuals can and do change partners during their lifetimes, they may practice serial monogamy. In other societies, polygamy is the marriage ideal. While polygamous unions usually begin as two adults, polygamy sanctions a marriage of more than two adults. When there is an ideal of one man with multiple wives, it is known as polygyny, and where there is one woman with more than one husband, it is called polyandry. How and who one marries is also regulated by rules of postmarital residence, including neolocal, patrilocal, matrilocal, avunculocal, and ambilocal types. Each of these is adapted to the descent rule utilized by the society in reckoning kinship.
Unilineal descent, with the creation of lineages distinguishing the husband from the wife, also involves marriage compensations, such as bride wealth, bride service, and dowry. Marriage compensation formalizes the alliance between the two lineages involved in the marriage and compensates one lineage for the loss of a young person and their offspring (as residence rules will require them to live with the lineage of their spouse). Remarriage obligations are also common in unilineal societies where the marriage is structured to endure even beyond death.