Love to know the answer to that question also.
From: azores@googlegroups.com [mailto:azores@googlegroups.com] On Behalf Of p...@dholmes.com Sent: Saturday, May 11, 2013 8:25 PM To: azores@googlegroups.com Subject: RE: [AZORES-Genealogy] Chromosome Browser for Family Finder DNA results I was just looking again at the Chromosome Browser for Family Finder and picked someone I believe is on this list - Vivian Christy. For my father, there are 11 shared segments between us. Some are slivers only maybe 2 or 3 cM wide. And if it weren't for the fact there is at least one larger than 7 cM wide, she wouldn't even show as a match. So we know that the larger the block, the closer the relative. So here's my question: Is there any reason to think that each of these 11 shared segments isn't representing 11 separate ancestors between us? The narrow ones might be common ancestors from 800 years ago, while the largest one might be 400 years ago. In other words, I think each separate segment is a separate ancestor. Can anyone explain why not? Am I right? For the benefit of anyone unable to follow this conversation with their own Family Finder kit, I am pasting in this graphic. Each of the orange bars is a segment marking where we match. I hope it shows up: Obrigado. Doug da Rocha Holmes Sacramento, California Pico & Terceira Genealogist 916-550-1618 www.dholmes.com -------- Original Message -------- Subject: RE: [AZORES-Genealogy] Chromosome Browser for Family Finder DNA results From: <p...@dholmes.com> Date: Wed, May 08, 2013 4:26 pm To: azores@googlegroups.com Here is my theory on how to understand the results of the Family Finder DNA test from ftdna.com. Feel free to add your own comments and punch holes in my theory. I would appreciate anything that helps me understand it better. What they abbreviate as cM are called "centiMorgan" and they define it as this: A centiMorgan (cM) is a measurement of how likely a segment of DNA is to recombine from one generation to the next. A single centiMorgan is considered equivalent to a 1% (1/100) chance that a segment of DNA will crossover or recombine within one generation. For humans, one million base pairs (bp) average about one centiMorgan. However, the rate of recombination is highly variable. I don't fully understand that, but what I think is that we can look at them as a representation of a person. When using the Chromosome browser, you will notice that you can choose the size of the cM block as either 1+ or 5+ or 10+ and this simply let's you decide how close or remote the matches you have and want to look at. If I choose people with only a 10+ cM block of DNA, that will eliminate a lot of the entire list of matches I can view. If I view a person who matches me in any way, most of the time there are more than one block of cM. It is my theory that this DNA came from one of my ancestors and so each tiny bit of cM is representing one ancestor. The larger the block, the closer the ancestor to present time. It's a closer relation to the person I match. The closest match other than a sibling would be to a parent. I have a total of 3382.22 shared cM with my father and the longest solid block of this cM is 267.21. I would love to hear from anyone who has tested a parent/child combo to see if my exact number is the same as yours. I suspect that if it were possible for me to test my mother, I would have slightly more or slightly less than for my father. If anyone has tested both parents and child, that would answer that question. My next closest match is as a 2nd cousin and I have 204.60 total cM in common with 23.64 as the longest block. If I had a first cousin tested, I would guess that I might share about 500-1000 shared cM and the longest block about 50-100 cM. If anyone has a match with a 1st cousin, I would love to hear what the numbers really are. After that, my next match is to a 5th cousin. We share a total of 50.96 cM and our longest block is 10.48. The next are a couple of relatives (father/son) which we have decided to list as 6th cousins, since there is nothing more remote to choose from. I believe they are actually 8th cousins. We share ancestors from Terceira and both of us have done extensive research and know all ancestors back to the 1500s on most lines. For the father, I have 46.35 total shared cM and for the son I have 47.94 cM. I can't explain why I have more from the son than the father, but that's what the results say. It might have to do with the above definition of cM in which there are variables in how it's formed. But for each of them I have exactly 19.53 as my longest block. I didn't realize until now that Mike Gilfilian doesn't show as my cousin - only for my father, despite the fact we are 5th cousins. I suppose it means I didn't inherit enough of our common ancestor's DNA for this to show. Maybe if I were to test one of my siblings, they would have that DNA I didn't get. If anyone has tested siblings and can comment on the results, I would be very interested. So I jump over to my father's results and find he and Mike share 28.82 total cM with the longest block of 10.83. They are 4th cousins, once removed. My above 5th cousin match in which I have 50.96 cM and our longest block is 10.48 is quite different for my father and this same person. Like Mike, this person is a 4th cousin, once removed and he shares a whopping 134.74 cM and longest block of 24.35. FTDNA says this falls into the range of a 2nd-3rd cousin. And that leads me to the next part of my theory. We have all noticed how these estimated relationships by FTDNA is simply wrong for our Azores ancestry. They always estimate a closer link than reality. Sometimes it's much closer. The reason for this seems to be because we have so many more remote ancestors in common than other countries they have tested for their entire database. These tiny 1+ cM segments that are just a sliver on the Chromosome browser all add up and up. They combine to form larger blocks and if the block is large enough, FTDNA will list them as a possible relative. In our case, the shortest block for any of my father's matches is 7.71. I suppose someone with a shorter block will not fall within the range of finding a relative within the last 200 years or so. It gets to the point that you're looking at what the sound professionals call "white noise" which is like listening to static from a radio station too far away to pick out any words or sounds. I would guess that 100% of the people who tested with Family Finder would all share at least a 1+ cM DNA segment. It might be from an ancestor 1000-2000 years ago, or more. Maybe it's the Celt with green eyes or the Frank with a hook nose. :-) In the above case of my father's 4th cousin, once removed, we both have Sao Roque do Pico ancestors. If we go back to the beginning of the records, we probably are related in 15-20 different ways. That shows up in the 134.74 total cM, not in the longest block of cM. Compare that to the 28.82 total cM of our other 4th cousin, once removed (Mike) in which we have 7 different ways we're related. In short, the total number of common ancestors who passed on their DNA (this supposes some didn't pass on their DNA - like with me and Mike not showing as related) will determine how close we appear to be related, but will not be the true relationship. It would have to be modified for Azores genealogy and many of those distant matches will fall off because they might be representing common ancestors from the 1400s, or something. Sure, I would love to learn that relationship as much as anyone else, but the reality is we can't learn it through church records alone. To further illustrate this false impression we get with the Family Finder test for us with Azores ancestry, I turn to another example coming from someone with a whole lot of Terceira ancestry and I don't think is on this list. For my father, this person shares a total of about 36 cM with the longest block of about 12 cM. We have ancestors from the part of Terceira of Santa Barbara, Sao Bartolomeu, Sao Mateus, and Doze Ribeiras. The closest actual relationship is 8th cousins, once removed. The common ancestors were married in 1646. But there are 14 different ways in which we are related. Another is 9th cousins, there are some 10th, 11th and more. Due to all these common ancestors, the predicted relation is as 4th cousin. Our 8th cousin link is to an ancestor born about 1620 and my father was born in 1919, so that's 300 years before. So much for the 200 year limit shown by Family Finder testing! If that were our only link, the total shared cM would surely be much lower and the projected relation be much further. So I think Family Finder really shows ancestors back to about 400-500 years ago, at least. It's just that you won't find the links in most cases. All our common ancestors added up and up and gave the false impression of a much closer connection. If we take it upon ourselves to come up with our own projections of relationship, we might have to say that the largest block be at least 10cM (up from the 7 cM threshold we now see). The projected relationship with someone sharing a 10 cM block might be 8th or 9th cousin. Another example comes from a 7th cousin, twice removed, who is projected to be a 4th cousin. We share 38 cM of DNA and the longest block is 12.75 cM. The common ancestor was born in 1629. But once again, because we have so many other more remote relationships, we get this false impression of a closer link. Another example comes from a 5th cousin, once removed, projected to be a 4th cousin. It's the most accurate estimate FTDNA made. The total shared cM is 27 and longest block is 13 cM. I believe this person is on this list (Kathleen Allen). Our common male ancestor was born very close to the 200 year estimate for Family Finder results. But we then come to another person on this list, Rosemary Capodicci, who manages her relative, Kenneth A. Silva's account. He has almost precisely the same numbers as Kathleen above - 28.96 cM and 13.03 longest block. Maybe it's not such a great example, because I don't know every branch of his ancestry. He has lots of Norte Grande ancestors and maybe one came from Pico and connects to me. If it goes as usual, we're 8th or 9th cousins, rather than the projected 4th. Sorry this turned out to be so long. You can imagine how much time it took to write! I hope some others will be willing to comment and compare findings. Doug da Rocha Holmes Sacramento, California Pico & Terceira Genealogist 916-550-1618 www.dholmes.com -- -- For options, such as changing to List, Digest, Abridged, or No Mail (vacation) mode, log into your Google account and visit this group at http://groups.google.com/group/Azores. Click in the blue area on the right that says "Join this group" and it will take you to "Edit my membership." --- You received this message because you are subscribed to the Google Groups "Azores Genealogy" group. To unsubscribe from this group and stop receiving emails from it, send an email to azores+unsubscr...@googlegroups.com. To post to this group, send email to azores@googlegroups.com. Visit this group at http://groups.google.com/group/azores?hl=en. -- For options, such as changing to List, Digest, Abridged, or No Mail (vacation) mode, log into your Google account and visit this group at http://groups.google.com/group/Azores. 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