>>> Please do go in to the details about males of different surnames having identical DNA matches. This has happened to me and I even consulted a prof of genetics and am still in the dark as to how this can happen. I appreciate the chart of probabilities that you sent to the list. <<< I, too, am part of the Family Tree DNA project, although I got into it through the National Geographic "Genographic project". It so happens that they used FT for the analysis, so I got in through the "backdoor". Originally, I had the minimum 12-marker Y-chromosome test, but recently upgraded to the full 67-marker test. They keep the original sample on file, so it's just a new order. btw - the sample is a swab from the inside of each cheek - quite easy to do by oneself. My 12-marker analysis revealed that I am descended on the male side from the Celtic gene pool that populates northern Ireland and Scotland (no great surprise there), but is not much help in identifying family connections - even with the same surname (as the percentages indicate). Speaking specifically about the Celtic/Anglo-Saxon model, men with the same surname can have different lineages because surnames are a relatively recent introduction to the British Isles. However, men with the same surname who trace back to the same area, or village, are probably related. The Y-DNA test only looks at the Y-chromosome (because only that is certain to be passed from father to son). Humans have 23 chromosome pairs (one from mom & one from dad) and only 1 of those pairs determines sex - the 23rd is either XX (female) or XY (male). (There are, of course genetic anamolies that result in XXY or other such combinations, but these are rare.) Furthermore, even the 67-marker test is only looking at about half of the genes in the Y-chromosome. (The Y-chromosome is the smallest - no jokes please - with 76, 85 or 125 genes, depending on what you read - I am no geneticist.) You could have matches on all 67 with different surnames because of adoption, fostering (a common practice in ancient times), or simply by name change (remember my comment about surnames). The match on all markers indicates a 99% match in 24 generations - but 24 generations is a very, very long time - I doubt many of us can with any accuracy trace that far. Y-DNA testing is, like any other source, just one more piece in the puzzle. Use it to narrow down your search, not as an end to your search. Brad Wilson [email protected] James > David > Moses > Russell > David > me Tartaraghan, Armagh > London, Ontario (only 6 generations, sigh)