Y-chromosomal Adam
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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 (the mt-MRCA), the matrilineal human most recent common ancestor, from whom all mitochondrial DNA in living humans is descended, although they lived at different times.

By analyzing DNA from people in all regions of the world, geneticist Spencer Wells has concluded that all humans alive today are descended from a single man who lived in Africa around 60,000 years ago.^[1]

However, because the earliest Homo sapiens sapiens is thought to have lived around 200,000 years ago, some doubt the validity of this assertion. Possibly there was a genetic isolation and remixing of early ancestral groups within Africa, with one group having been relatively more isolated and therefore having a higher predominance of an ancient Y-chromosome haplotype extant in their culture.^[2]

Naming

Y-chromosomal Adam is named after the Adam of the Genesis account of creation as a metaphor only. The name may seem to imply that Y-chromosomal Adam was the only living male of his time, but he probably co-existed with a large population of human males. None of Y-chromosomal Adam's contemporaries, however, have a direct male line to the present day. Either their lines died out, or they had at least one generation within each line that did not produce sons.

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 at least 30,000 years, or possibly a thousand generations. This is due to the differences found in male and female reproductive strategies.

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 was first pointed out, in the number of descendants of male vs. female fruit flies, by Bateman, 1948.)

Y-chromosomal Adam was not the same individual at all points in human history; 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, patrilineal lines are less likely to die out than during a population bottleneck.

References

1. ^ Documentary Redraws Humans' Family Tree
2. ^ "Human line 'nearly split in two'".

See also

• Paternal mtDNA transmission
• Y chromosome
• Human Y-chromosome DNA haplogroups
• Single-origin hypothesis
• Adam's Curse (book by Bryan Sykes)
• Genetic genealogy
• Mitochondrial Eve
• Most recent common ancestor
• Y-chromosomal Aaron
• San people
• Genealogical DNA test
• Genographic project
• Identical ancestors point

External links

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