Amy, One atDNA process I'm using now might help you - it starts to pay off as you confirm some Common Ancestors. Download your atMatches (yes 5 at a time) from the Chr Browser, and collect them all into one spreadsheet. Next I sort on Longest cM and delete the shortest ones (every atMatch at FTDNA has at least one segment that is 7.7cM or larger, so this might be a good cufoff). Then sort the remaining records by Chr and Start Loc. This arrays all of your large segments from the beginning of Chr 1 to the last one on Chr 22. You can easily scan down this list to see overlapping segments. At any one place on a chromosome, you can only have a segment from a paternal ancestor and a maternal ancestor - no more. So if you already know a segment is attributed to a particular ancestor, then you have a 50/50 chance that any overlapping segments will go back to the same ancestor. You can easily query the atMatch with that segment and see if he/she also has your known cousin as a match. If they match, you can be pretty sure the 3 of you descend from the same ancestor; if they don't match, then it might be that they still have the same ancestor, but not enough matching atDNA to make the cut, OR they share an ancestor that comes from your other parent. In actual practice with overlapping segments, you can make a judgement call - segments which look very close to each other (or one is twice the other) are probably from the same ancestor. If the segments are really staggered (visualize two courses of bricks - one course representing paternal segments, one for maternal segments), they are probably from different ancestors. The dividing places between segments (think brick joints) are random and may or may not line up (comparing maternal and paternal segments) - except, of course, at the beginning and end of a chromosome. It was hard for me to work this concept out in my head, but once I understood it, it has been a powerful new tool with atDNA. Jim Bartlett On 05/16/12, Amy Martin<[email protected]> wrote: I thought it might be helpful to know the following, in response to Karen's question: My 87 year old Mom has deep roots to colonial VA and NC in each of her known lines. She has about 240 cousin matches as of today (FT DNA). She tested 10 months ago. (18) are estimated 3rd cousin matches, (3) of which we have positively confirmed through our paper trails. Of these 3rd cousins, the longest cM segments range from 58-16. She has (30) estimated 4th cousin matches, one positively confirmed through paper trail. Of these 4th cousins, the longest cM segments range from 25-12. We've also positively confirmed a few others more 'distant' as well. In addition, there are dozens more oh so close, but just beyond the evil brick wall. I'm convinced the success of more confirmations lies with 'trench research' and communication. Amy > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 16 May 2012 19:07:05 +1000 > From: Karen Hodges <[1][email protected]> > Subject: Re: [AUTOSOMAL-DNA] Our atDNA matches are our cousins > To: [2][email protected] > Message-ID: > <CANvDYaVDBFojMt_-iYcJCLb3XjYz2E[3][email protected]> > Content-Type: text/plain; charset=ISO-8859-1 > >>> Parents and 1st cousins - virtually 100 percent >>> 2nd cousins about 99 percent >>> 3rd cousins about 90 percent >>> 4th cousins about 50 percent >>> declining percentages beyond that >> > > Hi Ann > > Can you tell me what size segments are typical of a fourth cousin, 50% ? > > Karen > > Dr Turner, > > I once constructed a spreadsheet specifically for atDNA. Empirically I found the number to be closer to 10,000 than 1,000,000. I got into a discussion with someone(Tim Jansen?) about a related subject. The thing that we both agreed on was that the order of magnitude of the number should be around 10,000. > > I abandoned the effort as trying to keep the trees synchronized required more effort than the small, 10,000 tree benefit. So, if both parties have all 10,000 ancestors and descendants of those ancestors in both of their trees with no errors, the chances of find 3rd or even 4th cousin matches should be quite good. My main tree is 40,000 plus names and includes numerous tree fragments attached to various DNA and other potential matches. A periodic "janitorial" that resolves duplicate entries finds most of my matches. > > > > Sam > ______________________________ For answers to Frequently Asked Questions about mailing lists, please see: [4]http://dgmweb.net/MailingListFAQs.html ------------------------------- To unsubscribe from the list, please send an email to A[5][email protected] with the word 'unsubscribe' without the quotes in the subject and the body of the message References 1. mailto:[email protected] 2. mailto:[email protected] 3. mailto:[email protected] 4. http://dgmweb.net/MailingListFAQs.html 5. mailto:[email protected]