Thursday, March 16, 2006

One Love

We are all descended from everyone. Everyone who has descendants.

Now think about your direct ancestors living 40 generations in the past, in
about the year A.D. 1000. The size of that group is harder to estimate. But as
two co-authors and I explained in Nature in 2004, that group included many millions
of people. Forty generations ago, almost everyone living today had ancestors in
Europe, Asia, and Africa, and many present-day Asians, Europeans, and Africans
had ancestors in the Americas because of the continual exchange of mates across
the Bering Strait.
It gets even stranger. Say you go back 120 generations,
to about the year 1000 B.C. According to the results presented in our Nature
paper, your ancestors then included everyone in the world who has descendants
living today. And if you compared a list of your ancestors with a list of anyone
else's ancestors, the names on the two lists would be identical.

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