Pokemon and Dragon Ball share the same universe If both franchises are set in the very far future, Humans could have evolved into the Saiyans before (or after) migrating (or relocating) to the planet Sadala. The Saiyans then conquered a new planet and named it "Vegeta", before Sadala was destroyed. The original Earth may actually be Sadala. In any case, as far as the inhabitants of the Pokemon World and Dragon World are concerned their world is still Earth. Someone at some point in the past of both franchises used the Dragon Balls to create two worlds filled with humans and magical creatures. Or three: why not the world of A Song of Ice and Fire too?