Bilateral Kinship – Tracing Descent through both the Maternal and Paternal Line

The term bilateral kinship is used by anthropologists to refer to the system of descent in which an individual is related to both their mother and father’s side of the family. This is in contrast to unilateral kinship, where an individual is only related to one side of the family.

There are three main ways of tracing descent:

1. Unilineal descent – tracing descent through one line only, for example matrilineally or patrilineally. In a patrilineal society, for example, a woman’s children belong to her husband’s patrilineage, and so they have kinship ties to his relatives rather than to her own. On the other hand, in a matrilineal society (such as the Na of China and the Mosuo of Tibet) the kinship group traces its descent through the mother’s line. In these societies, a man’s children belong to his wife’s matrilineage, and so they have kinship ties to her relatives rather than to his own.

2. Ambilineal descent – tracing descent through either the mother’s or the father’s lines, depending on circumstances and what is in the best interest of the individual or clan.

3. Bilateral descent (also called Cognatic kinship)– tracing descent through both the mother’s and father’s lines, without needing to choose between the two.

The vast majority of societies are bilateral. This means that they trace descent through both the mother’s and father’s lines. This system is also known as cognatic descent.

Bilateral kinship descent can create complexity but are more flexible

Bilateral kinship systems are far more complex than unilineal ones, as they involve a larger number of kin relationships. In a unilineal system, everyone is related to one another in the same way (e.g. as cousins or second cousins), but in a bilateral system, people can be related to one another in many different ways (e.g. as mother’s brother’s daughter, father’s sister’s son, etc.).

Bilateral kinship makes it possible for a member of a tribe to be part of two different clans (or lineages), which gives them a sense of belonging to both groups. It is thus more flexible than unilineal descent, enabling people to maintain relations with both lineages, while still making it possible for them to focus on one side of the family (or clan) should they choose to do so.

Bilateral Kinship Systems tend to be Exogamous

Bilateral kinship systems are more common in societies that practice exogamy (marriage to someone outside of one’s own social group) than in those that practice endogamy (marriage to someone within one’s own social group). This is because exogamous relationships create a need for people to have multiple kinship ties to different groups of people, which can only be accomplished through a bilateral system.

Endogamous relationships, on the other hand, do not require people to have multiple kinship ties to different groups of people, and so a unilineal system is sufficient.

Related Terms:

Unilineal descent – tracing descent through one line only, e.g. matrilineally or patrilineally.

Ambilineal descent – tracing descent through either the mother’s or the father’s lines, depending on what is in the best interest of the individual or group of people.

Cognatic descent (aka bilateral descent) – tracing descent through both the mother’s and father’s lines, without needing to choose between the two.

Kin relationships – the relationships between people who are connected to one another by blood or marriage.

Family tree – a diagram that shows the kinship relationships between people in a family.

Patrilineal descent – tracing descent through the father’s line only.

Matrilineal descent – tracing descent through the mother’s line only.

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