A surname itself gives us limited, general information about the origin of a family. DNA-testing can give us concrete evidence for identifying and separating family lines. Y-chromosome DNA testing is especially helpful because the male Y-chromosome is handed down, father to son, unchanged through the generations, except for rare mutations which, in themselves, can be helpful indicators of branching. The accessibility and affordability of family DNA testing is doubtless the greatest technical advance in the history of genealogical research because -- at long, long last -- we have a tool to break down those brick walls!