This is the first time I heard this theory. Where's the source? Knowing the source of a hypothesis will help us decide whether it's reliable or not. Personally I don't think we are outcasts, as if some outside force has, through magic, thrown us on this planet. First of all, Buddhism does not believe in a God. Secondly, one's existence, whether on earth or elsewhere, is determined by our karma as long as we are not enlightened.
I know of an explanation for population explosion on earth. It comes from Lama Yeshe when asked why the population is expanding all the time. Lama Yeshe said that like modern science, Buddhism talks about the existence of billions and billions of galaxies. The consciousness of a person born on earth may have come from a galaxy far away, drawn here by the force of karma, which connects that person's mental energy to the planet. On the other hand, the consciousness of a person dying on this earth may at the time of death be karmically directed to a rebirth in another galaxy, far from here. If more minds are being drawn to earth, the population increases; if fewer, it declines. That does not mean that brand new minds are coming into existence. Each mind taking rebirth here on earth has come from its previous life - perhaps another galaxy, perhaps on earth itself, but not from nowhere - in accordance with the cyclic nature of worldly existence.
This explanation indicates that the 6 realms of existence includes all the galaxies of the universe. We could have come from other planets. Amazing yet believable. It's our karma that propels us here, not God. It also shows how interconnected all beings are, and how much we depend on each other for our existence. We exist because the other exists. Pure and simple.