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, although they lived at different times, approximately 100,000 years apart.

[edit] 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.^[1]

“

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]

Wells says his evidence based on DNA in the Y-chromosome indicates that the exodus began between 60,000 and 50,000 years ago. In his view, the early travelers followed the southern coastline of Asia, crossed about 250 kilometers [155 miles] of sea, and colonized Australia by around 50,000 years ago. The Aborigines of Australia, Wells says, are the descendants of the first wave of migration out of Africa. ^[3]

”

The same article just below side 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 parental 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 ^[8]

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

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

[edit] 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.

[edit] Time frame

Y-chromosomal Adam probably lived between 60,000 and 90,000 years ago^{[citation needed]}, 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.

[edit] References

^ [http://news.nationalgeographic.com/news/2002 /12/1212_021213_journeyofman.html Documentary Redraws Humans' Family Tree]
^ "Human line 'nearly split in two'". April 24, 2008. http://news.bbc.co.uk/2/hi/science/nature/7358868.stm.
^ [http://news.nationalgeographic.com/news/2002 /12/1212_021213_journeyofman.html Documentary Redraws Humans' Family Tree]
^ Dorit, R. (1995). "Absence of polymorphism at the ZFY locus on the human Y chromosome". Science 268: 1183. doi:10.1126/science.7761836.
^ Paabo, S (1995). "The Y chromosome and the origin of all of us (men)". Science 268: 1141. doi:10.1126/science.7761828.
^ ^a ^b Deknijff, P (2000). "Messages through Bottlenecks: on the Combined Use of Slow and Fast Evolving Polymorphic Markers on the Human Y Chromosome". The American Journal of Human Genetics 67: 1055. doi:10.1016/S0002-9297(07)62935-8. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B8JDD-4RDBM6J-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=937048156&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=b19377a646d4cbf3dea4cde99e4bd6bf.
^ Weiss, G. (1996). "Estimating the Age of the Common Ancestor of Men from the ZFY Intron". Science 272: 1359. doi:10.1126/science.272.5266.1359.
^ Weiss, G. (1996). "Estimating the Age of the Common Ancestor of Men from the ZFY Intron". Science 272: 1359. doi:10.1126/science.272.5266.1359.

"Modern Men Trace Ancestry to African Migrants", A Gibbons, Volume 292, Number 5519, Issue of 11 May 2001, pp. 1051–1052.
"African Origin of Modern Humans in East Asia: A Tale of 12,000 Y Chromosomes", Yuehai Ke et al., Science 2001 292: 1151-1153
Bateman, A. J. 1948 Intra-sexual selection in Drosophila. Heredity2, 349-368.