taf wrote: "It is an monstrous overstatement to call this a marker of descent from Robert III. The mutation could have happened in any generation between Robert and Archie - it may have first arisen in Archie himself. Assuming the facts stated are true (that Archie descends from Robert, that Archie has a mutation not shared by descendants of Robert's brothers), then anyone who has it must share the same line as Archie and descend from Robert, but that doesn't mean that all descendants of Robert must have it. Any branch that split off before the mutation happened would still have the 'ancestral' Stewart subtype, even though they also descends from Robert." Well if the claim is to be taken seriously it could mean that they could actually triangulate and test several lines descended from siblings in several generations. If several sons of Robert have male lines still existing, it would show that Robert almost certainly did. If Robert also had siblings himself with surviving male lines, and these could be shown NOT to have it... that would be pretty convincing. And of course this should involve a good SNP marker that does not jump back and forth. Whether they really did that... we shall have to see. Would be a surprise to see such a thorough study, but that SHOULD be how they are done. Triangulation is often the key to really good genetic genealogy. :)