I had my dad's DNA tested last year at www.familytreedna.com.  We did the 67 marker test.  The results were interesting.   My dad is a direct descendant of David Thompson, b. 1703 Scotland, who first appears in 1732 in Guilford, CT.    From their database, he had several matches.  What was interesting was that out of those matches, the surname Macmillan kept showing up.  To our knowledge there is no Macmillan MALE blood in our line.  And, we weren't able to match up ancestors over in Scotland prior to the 18th century, because I hit a brickwall with my research.   On researcher suggested that my Thompson line once had the surname Macmillan and changed it some time back in history (maybe even when David came to the US in 1732).  Or, maybe a female ancestor had some secret.  I don't know if I'll ever figure it out.   All I can say, is that it is interesting to get the DNA tested, and periodically they run specials, so look for those.   Tracy Thompson Tomaselli Guilford, CT