![]() ![]() ![]() This group excludes the red person because their beginning point is not the same, or even close. Group 2 – However, if you look just at the blue and orange triangulated matches bracketed in green, I triangulate on slightly more. Group 1 – On the left group of matches, above, I triangulate with the blue, red and orange person on the amount of DNA that is common between all of them, shown in the black box. I triangulate with these matches in different ways, forming multiple triangulation groups that I’ve discussed individually, below. “I” am the grey background against which everyone else is being compared. ![]() You can see that I match 5 different cousins who I know descend from my father’s side on chromosome 15 above. However, what you’re likely to see is that some people don’t match on the entire segment, meaning more or less than others as demonstrated in the following examples. Triangulation means that all three, or more, people much match on a common segment. Reasonably sized segments are generally considered to be 7cM or above on chromosomes 1-22 and 15cM or above for the X chromosome. ![]() You can confirm mathematical triangulation, numbers 1 and 2, above, without knowing the identity of the common ancestor. Without triangulation, you might just have a match to someone else by chance. Triangulation is the foundation of confirming descent from a common ancestor, and thereby assigning a specific segment to that ancestor. On the same reasonably sized segment of DNA and.At least three (not closely related) people must match.Think of triangulation as a three-legged stool – a triangle. If you don’t need the tutorial, skip to the “Triangulation at 23andMe” section. This first section, “What is Triangulation” is a generic tutorial. You may want to read the introductory article first. This article, and the rest in the “Triangulation in Action” series introduces triangulation at FamilyTreeDNA, MyHeritage, 23andMe, GedMatch and DNAPainter, explaining how to use triangulation to confirm descent from a common ancestor. The “Home Run” article explains why you want to use a chromosome browser, what you’re seeing and what it means to you. Recently, I published the article, Hitting a Genealogy Home Run Using Your Double-Sided Two-Faced Chromosomes While Avoiding Imposters. ![]()
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