Comment by ice_man

On a related note, I have always found this fascinating: How many n * "great" grand parents do you have? Up to 2^(n+2) (Assuming an ancestral tree (as opposed to a graph) (i.e. no inbreeding). Assuming a 20-year generation length, that means that you have somewhere on the order of 10^6 great great great great great great great great great great great great great great great great great great great great grand parents, all of whom were frolicking all over the world in the 1600s.