The Shallow Roots of the Human Family Tree

Yahoo News has a very interesting article called Roots of human family tree are shallow. It's essence is this: Not too long ago, say 2000 to 5000 years, there lived a person which is an ancestor to all now living people. And a little longer while back, between 5000 and 7000 years ago, every person living then either an ancestor to all people living today or their line died out.

It's pretty amazing and sounds ridiculous until you read the article. The math needed to get an intuition for this is dead simple. I won't spoil the fun here, I recommend instead that you read the article. It's a lot of fun!