Linda, A very valid question. >>> That you so much for that explanation ~ it really helped me see more clearly how all of this works. Would you also know why there are so many different surnames associated with my father's (and other lines in my family for that matter) DNA? And from what I am seeing with his test results, if the other tester's do not know anything about their lineage it's nearly impossible to nail down a hit! Thanks for any other light you can shed on this topic. <<< As others have pointed out, there are 2 things which impact yDNA grouping. 1. Random mutations occur over time, but the probability of a mutation occurring is known from extensive testing over many years. The number of differences between 2 men's yDNA results indicates how far back they must go to find a common ancestor. The more markers tested (say Y-37 vs Y-12) to more precise the measurement. 2. Different surnames could be the result of adoption or fostering (where a son was "given" to another family to raise in order to build ties between families). Also, some cultures used to name children based on the father's (or mother's) name - so Will's son was known as John Willson, and John's son George was known as George Johnson, etc. I have several 2-step matches to my Y-67 results - and *none* of them is surname Wilson. DNA matching is generally over long periods (20 generations or more) and most people will never be able to trace that far back because records often don't exist. Brad Wilson