That's just it.
I don't.
On Lostorum, people believe what they will and that belief can even grant them great magical power, to the point such a believer can make others believe through the manifestation of that power; but, ultimately, "proving" God's existence on Lostorum is as nebulous a concept as it is here.
Those of faith believe "The Veil" (the southern aurorae) separates the land of the Gods ("The World That Was") from the land of the Mortals ("The World That Is.") The Gods and Mortals were divided from each other long ago, and mortals pass to the other side of the veil when they die. But the Gods cannot and do not walk the lands; you can't summon angels or demons (merely shadowy "projections" of them which are easily written off as illusions or hallucinations.)
So evolution is not out the Window on Lostorum, and in fact Lostorum's Darwin is just now writing Lostorum's version of The Origin of Species, Lostorum being in the midst of the railroad boom. The "missing link" problem will be massive, though, as humans do not have a common ancestor in Lostorum's fossil record. Many theories exist concerning why that is - from "%deity% created us" to "humans came to Lostorum from another planet" (the latter being derided by the former, naturally.)