In genetics, the most recent common ancestor (MRCA) of any set of organisms is the most recent individual from which all organisms in the group are directly descended. The term is often applied to human genealogy.
The MRCA of a set of individuals can sometimes be determined by referring to an established pedigree. However, in general, it is impossible to identify the specific MRCA of a set of individuals, but an estimate of the time at which the MRCA lived can often be given; such estimates can be given based on DNA test results and established mutation rates, or by reference to a non-genetic genealogical model. This time estimate is referred to as TMRCA in scientific papers.
The term MRCA is usually used to describe a common ancestor of individuals within a species. It can also be used to describe a common ancestor between species. To avoid confusion, last common ancestor (LCA) or the equivalent term concestor is sometimes used in place of MRCA when discussing ancestry between species.
The term MRCA may also be used to identify a common ancestor between a set of organisms via specific gene pathways. Mitochondrial Eve and Y-chromosomal Adam are examples of such MRCAs.
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Subject: Most recent common ancestor 
Tue Dec 14, 2010 9:08 am