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 <[email protected]> > Subject: Re: [AUTOSOMAL-DNA] Our atDNA matches are our cousins > To: [email protected] > Message-ID: > <[email protected]om> > 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 >