Bilineal descent is system of family descent where blood links and rights of inheritance through both male and female ancestors are of equal importance.
Tracing kinship through both parents. The most common form is bilateral descent. A system of tracing descent through both the mothers and fathers sides of the family.
A cloned child has unilineal, not bilineal, descent; he
or she is genetically kin to only one progenitor. What is more, the genetic kinship is
near-total: the cloned child is not genetically unique, but shares almost completely the
genetic endowment of the "original" progenitor.
The Daughters of the American Revolution is a bilineal descent category. The descendants of Abraham Lincoln may be defined as a bilineal descent category.
The Yško of southeastern Nigeria are an example of a
society with bilineal descent. Their important portable property, including livestock and
money, are inherited matrilineally. Fixed property, such as farm plots, pass down through
the patrilinal line as do rights to trees and other forest products. It is not surprising
that they have patrilineally inherited obligations to cooperate in cultivating their
fields. Obligations to perform funerals and pay bride price for sons are inherited through
the matrilineal line.
There are several ways of tracing descents. Unilineal Descent or one-line descent is that form of descent in which a relationship is emphasised through one sex or line. It is of two types:
1. Patrilineal or Agnatic Descent is a form of unilineal descent traced through males only. It is important to remember that the person calculating descent may be either female or male. Females in a patrilineal descent trace their descent through the line of their fathers as male members do.
2. Matrilineal or Uterine Descent is a form of descent traced through females only. Both females and males trace their descent in this way.
3. There is also the form of Double or Duo lineal or Bilineal Descent. It is a form of unilineal descent which combines both patrilines and matrilines. Descent is traced separately through female and through male lines for different purposes, e.g., inheritance of immovable property through one line and inheritance of movable property through the other.
Cognatic or Bilateral Descent is non unilineal descent. Here descent is traced through all progenitors, female and male, through both the mother and the father.
In India we generally find the patrilineal and matrilineal descent systems. Of the two, patrilineal descent system is more common. Patrilineal descent is more prevalent in North India. Among the tribals, many tribes such as Santhals or Mundas have the patrilineal system. Interestingly the polyandrous Todas too have a patrilineal system.
Tribes such as the Khasis and Garos of North-East have the matrilineal descent system. The Nayars of Kerala are a good example of matrilineal descent.
Unilineal descent groups often take the form of lineages and clans. Lineage is a set of kin, whose members trace their descent from a common ancestor through known links. A clan is often composed of related lineages. A clan is a set of kins who believe that they have descended from a common ancestor but cannot specify the genealogical links with her or him. - Extract from: Amit Kumar Sharma, NCERT XII Structure Of Indian Society.
In matrilineal descent, descent is traced through mothers rather than through fathers. Matrilineal societies, property is often passed from mothers to daughters and the custom of matrilocal residence may be practiced.
Patrilineal Descent is a system in which family descent is reckoned through the blood links of males. Typically names and property follow the male line of descent. A man's descendants are his own children, and women are little recognized as ancestors.
In matrilineal societies, the descendants of men are their sister's children and not their own, who belong to their mother's matrilineage.
Matrilineage is sometimes associated with polyandry or
group marriage where women have a variety of sexual partners and lines of male descent are