I agree with Alan.  It doesn't make sense to me for people to have the wrong idea either.   Look at his statement - "By *definition*, all males whose Y-DNA is in a particular Haplogroup have a common male ancestor!"    The definition doesn't tell us if we are talking about the Haplogroup defined by the high order SNP or by the terminal SNP.  Look at http://www.isogg.org/tree/ISOGG_YDNATreeTrunk.html    One of the high order SNPs is P305 and it is a defining SNP for Haplogroup A0, everyone should have P305, which would mean we all have the same common ancestor..  Sorry, I don't think that is what any of us mean by "common male ancestor".   If the definition doesn't mean the high order SNP it must mean the low order or terminal SNP.  Please look at the SNP names in red, they have all been added this year. Click on any of the Haplogroup names in the blue boxes. Try R.  See all of those red SNP names.  They have been added this year.  Just a wild guess on my part, but I'll bet we haven't found all of the terminal SNPs yet, thus we don't know all of the Haplogroup names, thus we can't define the group of men in the same terminally named SNP Haplogroup.   When I started this FTDNA said I was in Haplogroup R1b1.  Today, based on my 23andMe SNP list, FTDNA would call me a R1b1a2a1a1b3 and look at all on the new Haplogroups below that.   The point of my original post was to say that if you were an I1, for example, you would not share a common paternal line ancestor with a R1, for example.  I stand by that statement with no modification.  I did go on to say that if you share the same deepclade test with another person, that did not prove you shared a common paternal line ancestor.  I stand by that statement with the modification that you must know your terminal SNP and I doubt that any of us really know it.  In most cases FTNDA doesn't report the currently known terminal SNPs because they are too new.   Alan and I disagree and that is good.  You have his point of view and you have mine.  You can believe either of us or neither of us.  You'll be hard put to believe both of us.   If you wish to comment further on this topic please send your messages to me at parino@flash.net or to Alan at apowell@nycap.rr.com  Please, no more post on this topic on the list.   Thanks. Jim Barrett - Timpson, TX Powell Surname DNA Project http://jpbdna.com/powell-surname-dna-project.htm --- On Sat, 9/15/12, Alan Powell <apowell@nycap.rr.com> wrote: From: Alan Powell <apowell@nycap.rr.com> Subject: [POWELL-DNA] Haplogroup Definition - yes, again To: POWELL-DNA@rootsweb.com Date: Saturday, September 15, 2012, 12:04 AM I apologize for rehashing this subject, and perhaps I have missed some of the conversation, but I can't let it go because it doesn't make sense to me for people to have the wrong idea. Please look at the following articles: http://www.familytreedna.com/understanding-haplogroups.aspx >From the FTDNA website: "A Y-DNA haplogroup is defined as all of the male descendants of the single person who first showed a particular SNP mutation. A SNP mutation identifies a group who share a common ancestor far back in time, since SNPs rarely mutate. Each member of a particular haplogroup has the same SNP mutation." http://en.wikipedia.org/wiki/Haplogroup >From wikipedia:  "In molecular evolution, a haplogroup is a group of similar haplotypes that share a common ancestor having the same single nucleotide polymorphism (SNP) mutation in both haplotypes. " By *definition*, all males whose Y-DNA is in a particular haplogroup have a common male ancestor! Does this mean that because two Powells are in the same haplogroup that they share a RECENT ancestor? NO!  Many of the people in the Powell surname project are listed as R1b1a2, for example. The estimates I found suggest that the common ancestor for this haplogroup was about 7000 years ago.  That's a lot of generations. I would be amazed if most of us can go back 400 years in our genealogy.  This where the STR mutations or "markers" come in. These markers are also part of the Y-DNA but are a separate concept from the SNP mutations. These markers mutate more frequently, on average from the SNP mutations. Different markers also mutate with different frequencies, on average. The studies that I have seen suggest that some of them see mutations every 10 generations while others only see mutations every 100 generations. Over 7000 years, these markers mutate enough on average such that two individuals in the same haplogroup may end up varying by a large number of markers (15+). For genealogical purposes, you need to be in the same haplogroup and have markers that are pretty similar. Out of 37 markers, for example, I start losing interest in other Powells if they are further than a 34/37 match. If you are interested and do some research, you will find that the current theory is that there is a common male ancestor to ALL living humans, but we are talking 140,000 years ago. You will also find somewhat of a similar scenario with females and mitochondrial DNA (which a mother passes on to all of her children). I also have to point out that I am specifically talking about genetic relations, not necessarily family relationships. There are non paternal events which occur which can make for exceptions when you are trying and determine family lines. If, for example, I adopt a male child and he takes on my Family name, if he has children if may be confusing  to future researches of my line, because, since he is not my genetic offspring, he could be in a different haplogroup and/or have entirely different markers...