>>48920036Who says the current sneasel is the original variant. Hisuian Sneasel could be the original, and then evolved along with Hisui/Sinnoh's landscape to what is currently found in Sinnoh, then spread outward.
Even if the original variant is the one found in Sinnoh now, it isn't hard to imagine a group of the species migrating to Hisui, adapting, and then going extinct as the Hisuian landscape and pokemon populations changed. Then another group of the original species migrating to Sinnoh and establishing themselves without the need to change.