Descend
Etymology
descend
c.1300, from Old.French. descendre, from L. descendere, from de- "down" + scandere "to climb," from PIE base *skand- "jump." Sense of "originate from" is c.1375. Descent is attested from c.1330; descendant "offspring" is from 1600.
Description
In evolutionary biology, a group of organisms have common descent if they have a common ancestor. "There is strong quantitative support, by a formal test" for the theory that all living organisms on Earth are descended from a common ancestor.
Charles Darwin proposed the theory of universal common descent through an evolutionary process in On the Origin of Species, saying, "There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one".
The last universal ancestor (LUA) (or last universal common ancestor, LUCA), that is, the most recent common ancestor of all currently living organisms, is believed to have appeared about 3.9 billion years ago.
In The Ancestor's Tale, Richard Dawkins coined the word concestor, as a substitute for common ancestor or most recent common ancestor. This new word is very gradually entering scientific parlance.
Descent and the family
Descent, like family systems, is one of the major concepts of anthropology. Cultures worldwide possess a wide range of systems of tracing kinship and descent. Anthropologists break these down into simple concepts about what is thought to be common among many different cultures.
- Descent groups
A descent group is a social group whose members claim common ancestry. A unilineal society is one in which the descent of an individual is reckoned either from the mother's or the father's line of descent. With matrilineal descent individuals belong to their mother's descent group. Matrilineal descent includes the mother's brother, who in some societies may pass along inheritance to the sister's children or succession to a sister's son. With patrilineal descent, individuals belong to their father's descent group. Societies with the Iroquois kinship system, are typically uniliineal, while the Iroquois proper are specifically matrilineal.
In a society which reckons descent bilaterally (bilineal), descent is reckoned through both father and mother, without unilineal descent groups. Societies with the Eskimo kinship system, like the Eskimo proper, are typically bilateral. The egocentrid kindred group is also typical of bilateral societies.
Some societies reckon descent patrilineally for some purposes, and matrilineally for others. This arrangement is sometimes called double descent. For instance, certain property and titles may be inherited through the male line, and others through the female line.
Societies can also consider descent to be ambilineal (such as Hawaiian kinship) where offspring determine their lineage through the matrilineal line or the patrilineal line.
