Comment: Your logic

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In reply to comment: The odds are really good (see in situ)

Your logic

is flawed.

You can't say he has 2^32 direct ancestors. It doesn't work like that.

Say John Plantagent had two kids, Bob and Dave. Bob falls over a cliff, leaving only Dave. Dave has two kids Sally and Keith. Keith is sterile, incapable of having kids and Sally becomes a devout nun vowing chastity, never having kids. That's the end of John Plantagent's blood line. Period.

To do things correctly you have to actually trace which offspring continued to have offspring down through time, but still have a common blood link. That's real genealogy.

Your number of over 4 billion people being directly related to John P. is absurd. There are only 7 billion on earth, and over 1 billion of those are Chinese alone.