eli5 How are so many ancestors possible?

507 views

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

14 Answers

Anonymous 0 Comments

You are almost correct, but you are forggeting a simple fact:
The more you go back the more likely it is that some of you ancestors were “on both sides of the family”. As in, some generations ago there was a couple who is the great-great-…-grandparent of both you father and you mother. The more you go back, the more such couples there are.

You are viewing 1 out of 14 answers, click here to view all answers.