The following is a Plus Edition article written by and copyright by Dick Eastman.
How many ancestors do you have?
It is a simple question and would appear to have a simple answer: Any of us can count the number of our ancestors by performing a very obvious mathematical progression: two parents, four grandparents, eight great-grandparents, and so forth. In the past twenty generations, you have a mathematical chance of having more than one million ancestors. Thirty generations produces more than a billion ancestors, and forty generations results in more than one trillion.
The numbers are correct from a mathematical viewpoint but deliberately ignore one obvious fact: there have never been that many humans on the face of the earth since the dawn of evolution! The reality is that it is impossible to have one trillion unique ancestors, regardless of the mathematics involved.