When does DNA prove a relationship? When is a triangulation group sufficiently large enough to prove descent from an ancestral couple? When is a shared DNA segment large enough to prove someone is your first (or second/third/fourth, etc.) cousin? At what point does the DNA prove that I am descended from Samuel Snell? When does the DNA prove that you’ve found your great-grandmother’s biological parents?
And this is, perhaps, one of the greatest misconceptions in the post-DNA era of genealogy.
What is Proof?
Genealogy is the study of lives and relationships. Accordingly, genealogists spend much of their time identifying, hypothesizing, supporting, and sometimes rejecting, relationships.
Unless you have direct knowledge of a relationship (and even sometimes when you do), you identify relationships using evidence that you’ve gathered from multiple different sources (including DNA, census, land, tax, vital, and many other types of records).