Mcra

Mcra

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 large set of individuals, but an estimate of the time at which the MRCA lived can often be given. Such time to MRCA (TMRCA) estimates can be given based on DNA test results and established mutation rates as practiced in genetic genealogy, or by reference to a non-genetic, mathematical model or computer simulation.

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. The TMRCA in the case of gene pathways will be different depending on how restrictive the choice of genes is. Choosing a very restrictive gene such as mtDNA which is only inherited along the female lineage Mitochondrial Eve or the male equivalent Y-chromosomal Adam are examples of such MRCAs which yields TMRCA estimates orders of magnitude further back in time than TMRCA if any possible line of descendancy is allowed. Such genealogies in reality trace ancestry of individual genes, not organisms. As a result, TMRCA estimates for genetic MRCAs are necessarily greater than those for MRCAs of organisms.