Hello Group, I should have explained it better than giving a general or simplified statement in comparing Y-DNA and genealogical "closeness." If two people match 25 markers to 25 markers with the same surname the 90% possibility of a common ancestor is a bit over 250 years or 10 generations using 25 years as a generation. While it is possible, as John Chandler mentioned, for them to be first cousins, the probability of them being related within 50 years or 2 generations is less than 60%. (using FTDNATip Report) This is why the paper trail is so important. As each person documents back in time toward a common ancestor they are eliminating a missing generation. With population growth, migration patterns and by documented history this documentation or paper trail eliminates other possibilities and Carpenter Y-DNA lines. If the two closely related Y-DNA related Carpenters trace back their ancestry to a single state or county - that makes their research more concentrated and likely to document a paper trail to a common ancestor. If you check out the Carpenter Cousins Y-DNA Project web page you will see over 10 designated Carpenter lines. http://members.cox.net/johnrcarpenter/index.htm By gathering together multiple Carpenter lines that have a commonality with Y-DNA, you can triangulate or predict what the markers of the common ancestor would have been. What makes this more complicated is some thing called mutation. The difference (mutation) between the Rehoboth and the Providence branch of the Carpenter families who most likely came over from England in the 1630s plus or minus a few years - <GRIN> for Gene - is a single marker called DYS 464d, which is 16 for the Providence branch (Group 2 on the Carpenter Cousins Y-DNA web page) and 17 for the Rehoboth branch (Group 3). In comparing the 25 markers for each group the match is 24/25. The genetic distance is 1. "1" is very close in the genetic sense. These DYS 25 markers change 1 mutation about an average every 500 years. Research is being conducted on some that appear to mutate faster. The time calculations of mutations are highly dependent on both the mutation rate and model assumed. Some Carpenters have a genetic distance of over 30 and this by testing the same 25 markers. This shows the great diversity of the Carpenter family of which we are just beginning to glimpse. Those Carpenters that match 24/25 markers are closely related. I am from the Rehoboth branch of the Carpenter family with a document paper trail to William Carpenter of Rehoboth who was born in England circa 1605. Using a Carpenter from the Providence line whose paper trail goes back to William Carpenter of Providence (born about the same time period of the other William) we come up with the probability of when we had a common ancestor. The 90% probability of me and the other male Carpenter's (Providence branch) common ancestor is about 450 years ago. This using FTDNATip Report - Some researchers say that this model is too generous in probabilities. Compare this to cumulative probability listed below - See "A)". We have a paper trail of about 400 years. We have a genetic probability of about 90% that our common Carpenter ancestor was born 450 years ago. That is two generations or first cousins in genealogy. That is getting very close. That the two William Carpenters are related as first cousins is possible but less likely than being them being second cousins or third cousins. Without a paper trial we can only predict the probability. We could say that we have a Very High probability that me (Rehoboth branch) and the other Providence Carpenter have a common ancestor within the last 40 generations or 1000 years. That is still close in the genetic sense when you undestand that our "humanoid" DNA has been around for at least 60,000 years. Previous Carpenter genealogies with poor documentation and found to be in error because of misreading of wills gave the common ancestor, also named William Carpenter (of Homme), as being born circa 1440 in England. This is about 160 years or 6 generations before our two William Carpenters that came to America. It is about then, I predict or give my best guess, is where our common Carpenter ancestor lived in time. It will be because of dedicated Carpenter researchers (with documentation) who are willing to give their time, money, skills and Y-DNA who will help solve this puzzle. I challenge every Carpenter to do their part in making this possible. A Carpenter may have had an ancestor who worked with wood or wielded a battle axe. A Carpenter may have been or still is a Zimmerman(n) or even a Carpender, Carpendar, Carpentier, Charpentier, Carpentero or other Carpenter name variant. They may have been adopted or they may have taken the name because they liked it, but they are still a Carpenter. Remember, a Carpenter is a Carpenter is a Carpenter! John R. Carpenter La Mesa, CA http://members.cox.net/johnrcarpenter/index.htm PS I only get digest mode. A) FTDNA has a web page explaining genetic distance at ... http://www.familytreedna.com/trs_gendist.html and what a 24/25 marker match with a genetic distance of 1 ... http://nitro.biosci.arizona.edu/ftdna/24-1-0.html These web pages show how cumulative probability relates to TMRCA (Time to Most Recent Common Ancestor). http://nitro.biosci.arizona.edu/ftdna/TMRCA.html ----- Original Message ----- From: "John Chandler" <[email protected]> To: <[email protected]> Sent: Wednesday, October 26, 2005 2:34 PM Subject: Re: [CARPENTER] Re: Y-DNA Testing for Christmas or Thanksgiving or ... > Gene wrote: >> But to say that the DNA project has proven them to be "closely" related >> is an >> overstatement. The limitations of the DNA test are such that only a >> broad >> inference can be made as to the interval--perhaps several hundred >> years--between >> the immigrant Williams and their nearest, common Carpenter ancestor. > > Gene is correct. Mathematically, the best guess at the interval would > be 8 generations, but the range of plausible values goes from 2 to 50 > generations (based solely on the DNA comparison). Actually, 1 > generation is also *possible*, but is very unlikely, based on the DNA > alone. The shared surname obviously favors the low end of that range, > but it's wise to keep in mind that the 2-generation interval (i.e., > 1st cousins) is just at the limit of being plausible. > > John Chandler > > ______________________________