@browncoat - It does say that it was a legend that they checked for the inion.
And unfortunately, looks can prove things about ancestry, just through simple genetics. You probably wouldn't have a prominent inion unless you inherited it from somewhere (genetics isn't quite that simple all the time, but close enough).
Of course, the idea of being judged on genetic material alone is foolish for a lot of reasons. Not least the fact that we still have such an incomplete understanding of it. It wasn't long ago that people thought you could divine personalities from the bumps of the head.
It's one of the reasons that human eugenics is such a terrible idea. We have no idea what we'd be tampering with, what we'd lose. And that's not even going into the ethics of it.