Just Who Are Your Relatives?

If we say a generation is 25 years (and for convenience we'll assume it's the year 2000 now), then the American Revolution was 9 generations ago. Someone 18 years old in 2000 could have about 512 ancestors then. What did you have in common with them?

Even accounting for physical and cultural barriers between people, everyone on earth is related to everyone else at a time depth of 2000-3000 years.