DNA Triangulation is the method of identifying blood relationships within the recent genealogical time frame by identifying a minimum of three non-closely related DNA matches who share an overlapping DNA segment on the same chromosome.
Let's break this down:
Not all DNA matches are blood-related within the recent genealogical timeframe. Eventually, we all are related to each other but we don't need to figure out how we are related to a DNA match that doesn't triangulate. That's why understanding this process is so important as well as the fact that having a blood match with someone doesn't always mean you're triangulating. We want to concentrate only on DNA cousins.
What is a non closely related DNA match?
"Your DNA Family" defines closely related DNA matches as 2nd cousins and closer (so that includes 1st cousins, Aunt/Uncle, Great-Aunt/Uncle, Half Siblings/Niece/Nephews/Uncle/Aunt/1st cousins).
If a DNA match is most probable (based on the amount of shared DNA) to be a 2nd cousin once removed or more distant, they qualify for triangulation. This rule is based on our experience gained from more than 1.5 million DNA matches.
Share an overlapping DNA segment on the same chromosome
Let's take a look at a real example, from one of my own triangulated groups:
Green marks the matching segments start/end position between two people. You can see that Simone and I share a DNA segment from start position 201.6 to end position 216.9. The orange part of this triangulated group is the DNA we inherited from our unknown common ancestor.
The green portion to the left or right of the orange portion is likely to be of the same common ancestor. You can see that Simone, Marco, and I inherited a larger part of DNA for this specific area of chromosome 2 than Robert shares with the three of us. With such smaller segments, this exhibits the randomness of DNA recombination rather than how closely we are to each other!
At Your DNA Family, triangulation occurs automatically by clicking on a "possible triangulation" card. (The app automatically organizes all your DNA matches per chromosome and overlapping locus and side.)
Within almost no time you have your first triangulated groups and then you can work with your DNA cousins on identifying the common ancestor from whom you all inherited this piece of ancestral DNA.