Shannara Lore: Elves not descended from humans? (minor spoilers)

I read about half of Sword of Shannara, I think, over twenty years ago. I remember having the impression that all the races in the book were descended via mutation from human beings.

Now I happen to be reading through some lore wikis about the Shannara universe, and they are saying that Elves were always around, that they didn’t turn up as mutations from humanity after the apocalyptic war.

My question is: Does this fact about the Elves appear to be something Brookes came up with later in the series, or was it made clear from the very beginning?

I think it was mentioned in the first book that the Elves were different, but not explained. Allanon, IIRC, said something to that effect. As I recall, it was spelled out in the second, The Elfstones of Sannara.

I’ll second that recollection. I rather liked the second book when I was a youngster. Now that thought makes me feel dirty, much like recollecting how I used to like Piers Anthony :D.