Thank you very much! I read your site with pleasure. I wish you success in your search!Thank you. I am the author of the shissem site. It is a purely amateur attempt to explain the science to myself. I am happy if someone else finds this of use. BTW, I am G2a-Z726 and trace my most distant known ancestor to West Yorkshire, in England c1550 and perhaps to the village of Heysham, in Lancashire, where my family first earned their surname.