[malakhi]

The theory I heard was that while the rest of the Sethites had intermarried with the Nephilim and Cain's line of descent that Noah's line of descent was pure Sethite. Is this a Jewish understanding?

Some Jews have advanced this view, but it is not a universally held belief.

[lockeliberty]

Some Jews have advanced this view, but it is not a universally held belief.

I take it that you are not one of those who hold to this view. It seems to me, from a Jewish perspective, this would make a lot of sense since genealogy is so important to the Jews.