His methodology aroused bemusement among genealogists, who usually start with themselves and work back. Doing it the other way around, picking a person and working forwards, ends leading to virtually meaningless results if you start going back too far – and 500 years is stretching it. I used the book to study the development of surnames and found it fascinating.
At this point, virtually every Jew, and probably almost every goy in Europe and the Middle East, is related to Avraham Aveinu, as well as to everyone else from that time. People were constantly moving around. Indeed, we have a mesorah, admittedly al pe kaballah, that every human had a common ancestor less than 5000 years ago (the goyim hold the common ancestor was probably more like several hundred thousand years ago).
Remember also that tools of genealogy don’t pick up converts, since we had to forge fake yichus for them since if the goyim knew someone converted they would execute them as a heretic. It also misses people who went off the derekh, whether or not they later returned, since it would have been loshon ho’ra to record such matters.
My response to someone who starts boasting of yichus is to point out I’m from the family of Adam ha-Rishon by way of Avraham Aveinu, and then ask them what they are descended from.