Again, not to put too fine an edge, and all that -
But, was the "knowledge of good and bad" inherited from the ancient parents (& only them) eating from that one tree?
Why do some people have more knowledge of good and bad than others in that case? I.E. - Cain versus Abel.
If sin is inherited, why do some seem to have inherited more sin than others? I.E. - Hitler versus Pope John Paul?