I think the answer depends on who you have to test and what information you have on the ancestors of your test subjects.  Those of us in the Green group can be quite certain we are related, but exactly how is still an open question.  Seven of us match on 37 markers.  Below are the known most ancient ancestors for our group:   James Powell b. 1759 - 36 marker match, 1 different James Powell b. ca1787 - 36 marker match, 1 different William M. Powell b. ca1805 - 1 exact match, 1 36 marker match, 1 different Josiah S. Powell b. ca1817-1820 - exact match Allen Powell b. 1822 - exact match James Dyson Powell b. 1824 - exact match on 25 markers, 1 36 marker match, 1 different Cyrus Powell b. 1825 - exact match William Powell b. ca 1830-1835 - exact match John Clay Powell b. 1841 - exact match James William Powell b. ca1856 - 36 marker match, 1 different   There's also a Dock McClelland who is a 36 marker match, 1 different but may be a Powell descendant(I think, the exact details aren't coming to mind at the moment).    There are several other groups that are clearly groups of related people.  It helps narrow the search, and if you are and exact match to someone who descends from a man who may be your ancestor, then that dramatically improves the odds that he is, or perhaps even makes it conclusive.  The problem is that you don't absolutes, you get percentages.  A 37 marker match with another person gives you these percentages:   83.49% that you share a common ancestor in the last 4 generations.   97.28% that you share a common ancestor in the last 8 generations.   99.55% that you share a common ancestor in the last 12 generations.   99.93% that you share a common ancestor in the last 16 generations.   99.99% that you share a common ancestor in the last 20 generations.   100% that you share a common ancestor in the last 24 generations.   I'm very interested, particularly after going over these percentages again, to see what we're looking at once we get our upgrades to 67 markers that we recently ordered.   Chris --- On Tue, 7/15/08, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: Re: [POWELL-DNA] Our Website To: [email protected] Date: Tuesday, July 15, 2008, 9:36 PM what i would really like to know is how "recent" in time it is or the "least" amount of generations i.e. mid 1800's ? maybe 4 generations ? for sylvia's "missing" unknown great grd f ?? Sylvia, I believe that any time back to at least 1700 would be a good time frame. Jim Barrett - Timpson, TX jim, my researcher wants to know how far back a 67 marker might go back.i told her perhaps as far as 1700s.is this about correct or is it much closer in time line?still learning,sylvia ferriter kit number 36906 james jones. Markers 13 - 25 and markers 38 - 60 have been added to kit 123778. Thanks. Jim Barrett - Timpson, TX - [email protected] Barrett Surname DNA - http://www.flash.net/~parino/barrett-family-dna-project.htm Powell Surname DNA - http://www.flash.net/~parino/powell-surname-dna-project.htm ------------------------------- To unsubscribe from the list, please send an email to POWELL-DNA- [email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message ------------------------------- To unsubscribe from the list, please send an email to [email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message ------------------------------- To unsubscribe from the list, please send an email to [email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message **************Get the scoop on last night's hottest shows and the live music scene in your area - Check out TourTracker.com! (http://www.tourtracker.com?NCID=aolmus00050000000112) ------------------------------- To unsubscribe from the list, please send an email to [email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message