Back up. According to statistical geneology, everyone living today is probably a decendent of every person living just 1,500 years ago (except for those people living 1,500 years ago who have no decendents today living). Have people live apart from others for a few hundred years, and the separated groups will soon having distinctive language, appearance, etc. Appearance will be related to predominent genetic backgrounds. But to say that today's this or that group of people is descended from some group living thousands of years ago is way overstated.
I don't believe this statement...