MRCA26 March 2020
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 exact 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 most recent common ancestor (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.
In organisms using sexual reproduction, the matrilinear MRCA and patrilinear MRCA are the MRCAs of a given population considering only matrilineal and patrilineal descent, respectively. The MRCA of a population by definition cannot be older than either its matrilinear or its patrilinear MRCA. In the case of Homo sapiens, the matrilinear and patrilinear MRCA are also known as “Mitochondrial Eve” (mt-MRCA) and “Y-chromosomal Adam” (Y-MRCA) respectively.
The age of the human MRCA is unknown. It is necessarily younger than the age of both Y-MRCA and mt-MRCA, estimated at around 200,000 years.
The Last Universal Common Ancestor (LUCA) is the most recent common ancestor of all current life on Earth, estimated to have lived some 3.5 to 3.8 billion years ago (in the Paleoarchean)
Dawkins lists “concestors” of the human lineage in order of increasing age, including hominin (human-chimpanzee), hominine (human-gorilla), hominid (human-orangutan), hominoid (human-gibbon), and so on in 40 stages in total, down to the last universal ancestor (human-bacteria).