A cloned child has unilineal descent, not bilineal descent; he or she is genetically kin to only one progenitor. What is more, in unilineal descent, the genetic kinship is near-total. The cloned child is not genetically unique, but shares almost completely the genetic endowment of the original progenitor. Many societies construct kinship groupings exclusively through the patrilineal line or matrilineal line and are called unilineal descent groups. Unilineal descent groups also assume important corporate functions such as land ownership, political representation and mutual aid and support. Unilineal descent is found in societies that construct kinship groupings, roles, and relationships by tracing descent exclusively through the patrilineal, or matrilineal line. Such units are called unilineal descent groups, either patrilineages or matrilineages according to the prevailing descent rule.
Unilineal kinship institutions occur at over twice the incidence of cognatic ones among the world's cultures. The ubiquity of unilineal descent systems may appear inconsistent with the predictions of kin selection. Bilateral kinship systems closely follow biological genealogies and would appear to be more consistent with individuals' inclusive fitness interests. Unilineal descent systems exclude half of one's biological kin, those related through either one's mother or one's father.
The powerful West African Ashanti kingdom developed within a matrilineal society. Accordingly, the heir to the throne is not the king's (Asantehene's) own child but his sister's son. A third unilineal form, dual descent, involves the presence of significant patrilineal and matrilineal groupings in single society. Their occurance is relatively rare. Conditions favoring unilineal descent Most commonly found among materially rich foragers, small-scale farmers, and nomadic pastoralists. Until early 20th century, approximately 60% of all societies traced descent unilineally. Many of these societies have disappeared or have been absorbed by larger societies that follow other descent rules.
Most cultures limit range of people through whom descent is traced by using principle of unilineal descent. Both males & females are members of a unilineal grouping, but descent links only recognized through relatives of one sex. The two basic forms of unilineal descent are referred to as the Patrilineal Descent and Matrilineal Descent systems.
Descent concerns the tracing of relationships through succeeding generations, i.e., who has descended from whom. There are several ways of tracing descents. In India we generally find the Patrilineal Descent and Matrilineal Descent systems. Of the two, patrilineal descent system is more common. Patrilineal descent is more prevalent in North India. 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.
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 Descent 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.
2. Matrilineal Descent or Uterine Descent is a form of descent traced through females only. Both females and males trace their descent in this way.
There is also the form of Double or Duo Lineal Descent or Bilineal Descent. It is a form of unilineal descent which combines both patrilines and matrilines.
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. Evans-Pritchard and Meyer Fortes argued that the Tallensi and the Nuer were primarily organised around unilineal descent groups. Such groups function are characterised by common purposes, such as administering property or defending against attacks.
Bilineal descent is system of family descent where blood links and rights of inheritance through both male and female ancestors are given equal importance. The most common form is bilateral descent.
The structure of
unilineal descent groups. Fortes, M. (1953).
positive contributions resulting from the study of African social organization
is summarized. Norms of critical value in social organization, marriage
regulations, incest prohibitions, the laws of homicide and warfare, are not
"absolute rules of conduct" but "are relatively obligatory in accordance with
the structural relations of the parties."
Double Unilineal Descent and Triple Kinship Terminology : The Case of the Kwanja of Cameroon. / Gausset, Quentin. Journal of the Royal Anthropological Society, Vol. 4, No. 2, 1998, p. 309-323..
Unlineal and Bilineal Descent: How Various Cultures Trace Their Heritage. Joe Norton.