eli5 How are so many ancestors possible?

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Posted elsewhere but would like explained like I’m 5.

What I can’t get my head around is: I had 2 parents, they had 4 (in total) who would have had 8 in a geometric progression, so going back even 1000 years or 20 generations (assuming an average lifespan of 50 years) is 2,097,152 ancestors for just me, and given that there is a reported 7.9 billion people on earth alive today it seems mathematically impossible that all those people could have existed.

In: 7

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Anonymous 0 Comments

You get to many of the same ancestors via various roots, so the same person may both be your mothers great great grandfather and also your fathers great great great grandfather.

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