So I can't help but wonder whether I'm missing something: 23andMe's "new experience" provides, at the bottom of a match page's left-hand pane, "relatives in common." As I understand it, anyone for whom "yes" is marked is part of a "triangulated group" consisting of "me," my 23andMe "DNA cousin," and all the other "yes"-marked folks in this RiC list. Correct? So, why does this list include anyone marked as "no"? Aren't those "no"s just chaff? In which case, why's 23andMe include them (thus forcing us to click through page after page of RiCs in order to find the few "yes"s)? Best, Eric

Dear Eric, The answer to your first question is "yes". The reason that 23andMe includes the people in the "no" category is that this information can be helpful if you are trying to organize clusters of related people. Let's say that you are one of 4 people who have tested at 23andMe and that these 4 people are all 4th cousins to each other on different lines of descent from a shared ancestral couple. Let's call these 3 cousins of yours A, B, and C to keep them straight. Let's say that you share the same segment of DNA with A and B and thus the 3 of you form a triangulated group. Let's say that C shares a different segment of DNA with you than the one you share with A and B and that C also shares a DNA segment with both A and B. It is helpful for you to know if A and/or B share DNA with C. In such situations 23andMe will enter a "no" in the Shared DNA column under C's name on the rows for A and B when you pull up C on your match list in DNA Relatives. A secondary question has to do with the probability that a small percentage in the column under C's name is genealogically significant when A and B share an HIR with C. There are several possibilities here: 1. The HIR that C shares with A or B is a false match. 2. The HIR that C shares with A or B represents a true shared segment (IBD) passed down through the same ancestral line that you share in common with A, B, and C. 3. The HIR that C shares with A or B represents a true shared segment (IBD) passed down through a different ancestral line than the one you know you share in common with A, B, and C. It is up to you to sort out which of the above the possibilities is the correct one. Chromosome mapping and using phased data can help you sort these issues out. I have often wondered what the probability is that cousins such as A, B, and C will have either option #1 above occur or option #3 occur. The probability of option #3 will of course depend to a significant extent on the degree of endogamy among A, B, and C. The higher the degree of endogamy, the higher the probability of option #3 occurring. The probability of option #1 is probably reasonably high if the shared percentage is 10% or less. So there is definitely some degree of "chaff" in the "no" column. It is up to you to sort the wheat from the chaff. I would like it if 23andMe would allow us to sort the Shared DNA column and the column next to it, but they haven't created that option yet. Sincerely, Tim Janzen -----Original Message----- From: GENEALOGY-DNA [mailto:[email protected]] On Behalf Of Eric S Johnson Sent: Sunday, November 26, 2017 4:38 PM To: [email protected] Subject: [DNA] 23andMe TGs So I can't help but wonder whether I'm missing something: 23andMe's "new experience" provides, at the bottom of a match page's left-hand pane, "relatives in common." As I understand it, anyone for whom "yes" is marked is part of a "triangulated group" consisting of "me," my 23andMe "DNA cousin," and all the other "yes"-marked folks in this RiC list. Correct? So, why does this list include anyone marked as "no"? Aren't those "no"s just chaff? In which case, why's 23andMe include them (thus forcing us to click through page after page of RiCs in order to find the few "yes"s)? Best, Eric