Triangulation/14/en
From ISOGG Wiki
The basics of triangulation for Y-DNA testing
Genetic genealogical triangulation is rather simple. Think of a triangle. /_\
Person A & B match genetically and that forms the base of the triangle. _
Person A has a paper trail (genealogy) that goes back in time. /
Person B has a paper trail that goes back in time. \
The top of the triangle is the MRCA or most recent common ancestor.
For Y-DNA testing: Person A is who you are testing. Some living biological male 2nd, 3rd or better cousin could be Person B. The most common shared ancestor is the MRCA.
For other DNA testing: Person A is who you are testing. Another person is Person B. The most common shared ancestor is the MRCA.