For this MH RP that may come up, I'm featuring two actual concepts that allow for such a Pre-dominant Monster environment to be a thing.

1). My original plan. This is a monster-only environment, but you start out as a Great/Drome creature. Through completing quests and killing large monsters, you earn evolution spheres, and when you reach enough you can evolve into a new creature. Progression info and branch is explained above.

2). Have a tiny human cast in a pre-dominant monster environment. A group of hunters battle against a mysterious elder dragon, which somehow teleports them into the future, where humans are extinct and monsters live in a hierarchical system akin to Planet of the Apes trilogy. There's Monster Kingdoms and the creatures can talk, and they reaaaaaaally dislike the humans. The hunters must earn their trust as they attempt to figure out how to get home.

Any other suggestions on what may pop out of this are most welcomed!