In The Book of the New Sun there are many variations of humans and other life forms. There are regular humans, ape-men and Zoanthrops, and probably some other variations. However while the autochthons are vaguely described as tribal and primitive, they are not necessarily described as human or sub-human. I believe at one point in the novel its alluded to that the autochthons are cacogens (extra-solar aliens).
What or who are they exactly?