Wait... What if humans were on Roshar (be it pre- or post-Shattering), had access to Surgebindings, fought wars with the Singers and got their Heralds and maybe even Knights Radiant, and then a sizable part of them was for one reason or another (a loss against the Parshendi?) forced to go to Ashyn (assuming that's the world they destroyed with Surgebinding), then on Ashyn they got to know Odium but also destroyed the world, then they returned to Roshar, starting the wars that we know as the Desolations?
Yes, it's very much out there, just throwing it in when it's late and, judging from the quality of the theory, I should really go to bed.