I feel it has been discussed before on Westeros as well, though I can't remember any specifics.
As for the concept of evolution, I actually do believe that the life in the Bakkerverse evolved, or at the very least, all the life on planets other than Earwa evolved. I say this because I think it fits into the idea of the Inchoroi being a race "born for damnation". Plus I'm pretty sure there are quotes from Bakker stating that lifeforms reaching a certain level of intelligence eventually develop a soul, which implies the movement from a lower to higher order, or a progression, rather than just snapping into existence.
As for how the Nonmen could exist in an evolutionary system -- they were rather segregated from the better part of Earwa for most of their history, and they do display features that could theoretically be consistent with humans that moved underground, and thus adapted to that lifestyle (pale skin, hairless, dark eyes, etc.).