Adam/Eve

Y-Adam and Mitochondrial Eve

Because the rate of mitochondrial genetic mutation is slow (slower than Y), it is used to document events by comparing it to mtDNA of other populations. When mitochondrial DNA from certain populations in Africa are sampled and compared with European mtDNA, the mutation differences between the two can be compared, and produce a timeline indicating when modern Europeans first left Africa.

The concept of Mitochondrial Eve originated with the comparison of worldwide mitochondrial DNA. Basic similarities in suggested that we all contain genetic material from a single woman who was living in Africa around 200,000 years ago.

Now, a single being cannot populate the entire earth, but there have been several so-called genetic bottlenecks resulting in a severe depletion of DNA. Surviving organisms then re-populated from the stock that was left. Eve would have had many ancestors, but she is at the beginning of one of these bottlenecks and she is now referred to as our most (mitochondrial) recent common ancestor – mt MRCA. She also would have lived with others of her kind and not been The MRCA in her time.

Whatever killed off most of those people at the time may have even killed her, but at least one daughter would have survived and thus her line lived – into today.

Y-Adam, MCRA

The same scenario would apply to Y-Adam except that he and Eve would have lived thousands of years apart – much closer to present day. While Mitochondrial Eve is thought to have been living around 140,000 years ago, the patrilineal human MRCA could have been living as late as 3,000 years ago. The MCRA is the one from whom all Y chromosomes in living men are descended, and as such, he is the counterpart to Mitochondrial Eve.

Y-Chromosomal Aaron

Y-chromosomal Aaron is the term for the most recent common ancestor of the patrilineal Jewish priestly caste known as Kohanim. Research published in 1997 showed that a large proportion of contemporary Jewish Kohanim share a set of Y chromosomal genetic markers, known as the Cohen Modal Haplotype, and they may descend from this single common ancestor.
Links
On the Common Ancestors of All Living Humans