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
There are two parts to the answer:
People share ancestors. Sibling have the same parents. They have parents who may have had siblings. People breed with cousins of various levels of remove. Some people didn’t breed at all. It’s not just a simply forever dividing tree.
Secondly, there are ~8 billion people alive today. There have been ***~100 billion*** homo sapiens since the species arrived.
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