Yeah because of genealogy records and they reverse engineer the results.
I'm not sure what you mean by that. But I did the ancestry.com thing a few years ago and it accurately connected me with many relatives across America that I'm familiar with.
I've worked though the family tree a bit and found that ancestry.com correctly sorted out some family history that wasn't common knowledge even within many members of the family.
It's been very accurate in the way that it linked things together.
