Today I tackle one of the biggest questions of the Pokémon universe; why does the Mystery Dungeon universe have no humans? As this is never explained explicitly, this has been subject to many debates. Normally, this would be simple. Different canon, no humans. But there is one case in point. The hero of the games. As that person used to BE a human, as well as the Pokémon's knowledge of the existence of humans, we know they exist. So, where are they?
One common theory is that the Mystery Dungeon universe is actually a post-apocalypse, far future version of the regular games in which all humans but one died from whatever caused, famine, war, disease, and such, but Pokémon weren't affected. Or it ended up like a Rise of the Planet of the Apes/I Am Legend scenario, which could explain the Pokémon's ability to speak and act civilized, as seen in Treasure Town.
Another, far less common theory is the co-existence theory, believing that the Mystery Dungeon planet is a separate world altogether from the regular games planet, and that Pokémon migrated there through either ancient or human technology, and the hero's presence is because he was a former astronaut or something like that. The problem is, how would the legendaries end up there?
So, why do YOU think the PMD world is free of humanity?