Y-chromosomal Adam

Y-Chromosome of a Human male

In human genetics, Y-chromosomal Adam (Y-MRCA) is the patrilineal human most recent common ancestor (MRCA) from whom all Y chromosomes in living men are descended. Y-chromosomal Adam is thus the male counterpart of Mitochondrial Eve, although they lived at different times, approximately 50,000 to 80,000 years apart.^[1]

Y-MRCA date

By analyzing the Y-chromosome DNA from males in all regions of the world, geneticist Spencer Wells has concluded that all humans alive today are patrilinealy descended from a single man who lived in Africa around 60,000 years ago.^[2]

The same article just below said that: "many archaeologists disagree, saying the fossil record shows that a first wave of migration occurred around 100,000 years ago".

In scholarly literature first "Adam" or rather first paternal ancestor date was estimated at 270,000 years ago.^[4][5] Later new set of markers was chosen and the age was adjusted to mostly cited value.^[6] The dates calculated on new markers was 37,000–49,000 years ago.^[7] to 51,000–411,000 years ago^[7]

The dates are calculated from present day distribution with assumption for unique mutation events (UMEs):

1. "no strange Y lineages were introduced into this population by means of migration
2. each UME occurred for the first time within our population
3. each UME occurred only once
4. detected all UMEs present in the male subjects studied"^[6]

Naming

Y-chromosomal Adam is named after the Biblical Adam. While the name implies that Y-chromosomal Adam was the only living male of his time, it is important to understand that he probably co-existed with a large population of human males. None of Y-chromosomal Adam's male contemporaries, however, have a direct unbroken male line to the present day. Either their lines died out entirely, or at least one generation within each line produced only daughters, who could not pass their male parents' and ancestors' Y-chromosomes to their own children.

Time frame

Y-chromosomal Adam probably lived between 60,000 and 90,000 years ago, judging from molecular clock and genetic marker studies. While their descendants certainly became close intimates, Y-chromosomal Adam and mitochondrial Eve are separated by tens of thousands of years.

The more recent age of the Y-MRCA compared to the mt-MRCA corresponds to a larger statistical dispersion of the probability distribution for a Paleolithic man to have living descendants compared to that of a Paleolithic woman. While fertile women had more or less equally distributed chances of giving birth to a certain number of fertile descendants, chances for fertile men varied more widely, with some fathering no children and others fathering many, with multiple women. (This difference in variance^{[citation needed]} was first pointed out, in the number of descendants of male versus female fruit flies, by Bateman, 1948.)

Genetics states^{[citation needed]} that in the ancient past, our Y-chromosomal Adam was not the common ancestor of the entire population, and in the future one of his descendants may take over. The Y-MRCA of all humans alive today is different from the one for humans alive at some point in the remote past or future: as male lines die out, a more recent individual becomes the new Y-MRCA. In times of rapid population growth such as the present, patrilineal lines are less likely to die out than during a population bottleneck.

See also

References

External links

• Documentary Redraws Humans' Family Tree (from National Geographic)
• Mitochondrial Eve and Y-chromosomal Adam Diagrams
• Y-Chromosome Biallelic Haplogroups