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==Description==
==Description==
'''''Ascending and Descending''''' is a [[Prints|lithograph]] print by the Dutch artist [http://en.wikipedia.org/wiki/M.C.Escher M.C. Escher] which was first printed in March 1960.
In [http://en.wikipedia.org/wiki/Evolutionary_biology 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.
[http://en.wikipedia.org/wiki/Charles_Darwin Charles Darwin] proposed the [[theory]] of universal common descent through an [[evolutionary]] [[process]] in [http://en.wikipedia.org/wiki/On_the_Origin_of_Species ''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 [http://en.wikipedia.org/wiki/The_Ancestor%27s_Tale ''The Ancestor's Tale''], [http://en.wikipedia.org/wiki/Richard_Dawkins 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 [http://en.wikipedia.org/wiki/Iroquois 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 [http://en.wikipedia.org/wiki/Eskimo 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.
[[Category: Biology]]
[[Category: Anthropology]]
[[Category: General Reference]]
[[Category: General Reference]]