David, I don't want to make light of your point as it is certainly correct, at least in some aspects. The need for testing does depend on the goal or goals you have. If all you are trying to do is confirm a cousin or 2nd cousin relationship of someone with the same surname/genealogical records; getting a match at 35 to 37 of 37 or of 24 to 25 of 25 is pretty convincing evidence. However, if you are trying to build an R1b1b2 based family tree and ascertain the various lineages going back several hundred years (where the genealogical records are unreliable or at least strained) then deeper testing is very important. Deeper testing is also very helpful for determining relationships between different families or surname variants, or within a purported clan, or in the case of potential NPE's. Also, deeper testing is very important if you are interested in deep ancestry and ties to ancient cultural expansions or movements. Regards, Mike On Sat, Jun 12, 2010 at 8:49 PM, David Willis <dwillis1@san.rr.com> wrote: > > I have a minority view: that testing beyond 37, or even 25, markers is > usually not helpful. > > I am the administrator of the Willis project at FTDNA. We have about 115 > members. About 70% of us match someone else in the project. We have about a > dozen groups of Willises (the name is derived from the name William and > originated in many different locations in Great Britain). > > By far the biggest benefit of Y-DNA testing for members of the Willis > project is that they find out which group of Willises they belong to. There > is no instance where testing beyond 25 markers would have been needed to > figure out which group to assign the member to. > > Interestingly, out of the dozen groups in the Willis project, only a couple > of them know who their common ancestor is. Solving this problem by > analyzing mismatched markers has not helped much, at least for me. When, > and > in whose line, did the mismatch occur? > > Dave Willis >