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A comment on Rare 'goat-sheep' born on Irish farm. Parent comment

Re:Rare 'goat-sheep' born on Irish farm by pcrh on Saturday April 05, 2014 @05:51AM (#7536558)
"You are descended from almost every single human being alive 1,000 years ago."

Not exactly 1,000 years, but more like 120-135,000 years for the male line [1], and 200,000 years for the female line [2].

[1] "Sequencing Y Chromosomes Resolves Discrepancy in Time to Common Ancestor of Males Versus Females " dx.doi.org/10.1126/science.1237619

[2] https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Mitoch...

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Re:Rare 'goat-sheep' born on Irish farm by Houshalter on Saturday April 05, 2014 @01:07PM (#7537628)
No it's much closer to 1,000 years. Every generation the number of possible ancestors you have doubles. 2 parents, 4 grandparents, 8 great grandparents. Within a few generations back, you have literally millions of ancestors.
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Re:Rare 'goat-sheep' born on Irish farm by bradleyjg on Saturday April 05, 2014 @04:18PM (#7538296)
Doesn't that assume no overlap? It seems like the odds of 2^n unique ancestors would be pretty low by the time you get to 10.
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Re:Rare 'goat-sheep' born on Irish farm by maxerickson on Saturday April 05, 2014 @04:35PM (#7538347)
This seems like a reasonable discussion of the issue:

http://gcbias.org/2013/11/11/how-does-your-number-of-genetic...

After ~15 generations your genealogical ancestors aren't all that likely to have contributed much to your DNA.

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