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...