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.

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Anonymous 0 Comments

You are more closely related to strangers on the street than you think. Those 2’097’152 ancestors aren’t just your ancestors. They are likely the same ancestors for most people in your country, if not even the whole planet.

Think of it like this: You have 1 kid. Your kid has 1 kid. Your grand kid has 1 kid. Your great grandchild is now related not just to you, but to your wife, your kids wife (and all her ancestors), your grand kids wife (and all her ancestors). And this isn’t even including siblings.

Theres a good chance you and I share the same ancestors if you go back just 10 generations.

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