My friends and colleagues know my aversion to online trees.
A first cousin of my wife's grandfather did a Family Finder test for me last year. She is as old as dirt. But even she was not yet born in the 1730s.
A week or so ago, I received a notice from FTDNA that someone added her to an online tree. There was a link which didn't work.
Eventually I found it. She was linked by name and kit as married to a man born in 1730 and they had a daughter born in 1735. (That's a good trick in itself!)
I wrote to the woman behind this tree and she insisted that although she knows this woman is My Wife (which she isn't), this tree is correct because it came up automatically. AND IT IS CONNECTED TO THE VILNA GAON!! Well then, what more can I say!
We went back and forth on this a few times. At some point she wrote "But I did assume that the link could be established back that far through MtDNA. Mother to mother, to mother."
But my wife's grandfather's cousin didn't do MtDNA!
Good luck to you. Doncha just love the fealty to technology? And the unbounded unfounded confidence.