How accurate are ancestory tests like 23andMe? Specfically, how accurate are ancestory.com's tests? So. My grandfather is a third generation Italian immigrant, he has a (apparently) very common Italian name, and we've always been told we were Sicilian.

However, he recently got his results back and it said we have no Italian in us at all.

In effort to keep a identity crisis from happening, how accurate are these tests?