2 parents, 4 grand parents 8 ggp 16 gggp.....pretty soon, more grandparants then the number of humans that ever lived. How the heck does that work?
Yeah, that's true. Working backward is an exercise in the powers of twos. However, if you want to get really interesting, work forward. At minimum, the power is 4. It is actually far more when you consider siblings. If you figure that each family had six children, then you end up with more people than are on the earth today.
Well, if you go back in your family tree in all branches, you will see the same individual popping up in several times different places within the same family tree.