One thing I've noticed with regard to DNA testing, while it does prove that there is a link between two people with known DNA, there is one flaw. Unless we dig up all known named graves in say Devon and take DNA samples we are unlikely to ever know exactly who in ancient Devon we could actually be descended from. DNA will show exactly where the generations join, but not who they were. To me there is only one possible way of knowing our ancestory is down the female line. Only one person can be the mother of a child, but any male can be the father. This still depends on if the information we have is of the correct mother. Unless we invent time travel, sorting out our family pedigrees will always be one of a lot of guess work.