The Demihuman Origin Theory

There are multiple species of demihumans and beastmen in Raphtalia World, even the 2 Heroes World have precursors of their base form races exist in the Era. So where does Demihumans and Beastmen come from?

I have an theory called the Forced Evolution Theory, basically the first world phase where the world have 1 Legendary Hero and its only inhabitants are humans. But the Legendary Heroes began to make companions from animals as combat pets to boost their party fighting capabilities. But the first evolution would be like pets because its in the Heroes games knowledge.

But as soon they become human, the first demihuman exist. But, I think something happened that someone noticed that the effect could worked in other animals and decided to make animal girls Harem, and that's why their are multiple Demihumans.

The 2 Heroes world would be the crossbreeding and magical experiments that created more monsters and demihumans if they could helped the Heroes in their quest. Because the normal leveling animals propably dissapear or removed in the world system. That's where the Hakuno was created, and probably the Aquatic Demihumans and peculiar ones.

The evidence is that Demihuman acted like Pokemon, where they grow faster in leveling up, and can reverted in original animal form upon having the Beast Form Skill.