Joseph Chang, a statistician at Yale, published a paper in 1999 in which he claims to demonstrate that if we go back not-so-many generations, every person then living who has *any* descendants living now has *all of us* as descendants. My take on this is that the idea that there are significantly different "blood lines" is more or less hooey. You can read a news story about this paper at: http://phenomena.nationalgeographic.com/2013/05/07/charlemagnes-dna-and-our-universal-royalty/ and the paper itself at: http://www.stat.yale.edu/~jtc5/papers/CommonAncestors/AAP_99_CommonAncestors_paper.pdf David Ewing