Quoted By:
"In the same way humans in our world are a type of animal, are humans in the Pokémon world a form of Pokémon?
Masuda: Humans are definitely separate from Pokémon. The way you think about it is different than how we think about animals in relation to humans on Earth. For example, on Earth we have mammals and reptiles all these different categories. In the world of Pokémon, they are all Pokémon. We don’t really categorize them in exactly that way. It’s kind of a different way of looking at it. So yeah, humans are definitely separate from Pokémon. For example, humans can’t learn four different moves like a Pokémon can."
So, if Humans AREN'T a type of Pokémon, that pretty much leaves two options...
1. They were created by Arceus after he saw us in our universe and how we interact with animals.
2. They were brought to the Pokémon world FROM Earth, by Arceus, in prehistoric times and evolved separately in a universe with new physics.
Humans, like actual plants, are life, but they aren't Pokémon...
But they couldn't have evolved from nothing in the Pokémon world...