A person's ancestry is interesting stuff.
And while ancestry is a topic, https://phys.org/news/2013-08-dna-earth.html
August 8, 2013
Researcher uses DNA to demonstrate just how closely everyone on Earth is related to everyone else
by Susan Bell, University of Southern California
Quote:
... "The fact that everyone has two parents means that the number of ancestors for each individual doubles every generation," Ralph said. "By using basic mathematics, we can calculate that ten generations ago each individual had a thousand ancestors, and 20 generations ago they had a million and so on.
"But when we get to 40 generations ago, in the time of Charlemagne, we arrive at a trillion ancestors and that is a problem because we now have more ancestors than there were people. Thus one can deduce that a lot of those ancestors must be the same person." ...
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