I've been looking into Zoroastrianism, and have been fascinated by how it seemingly very strongly influenced the Abrahamics. It sort of leads me to a weird sense of "this religion is more authentic because it didn't take from another like those did." Clearly that's not the most brilliant idea, I know. But aside from the fact that it may have actually done the reverse and taken some from Islam in later years, what about what came before? What inspired it? How far back can we go in this chain to a reasonable knowledge of a precursor faith?