Oh, so the writer of "Smile" is the same person who wrote "In the Forest of the Night"! That explains a lot. I thought it was a new guy.

Bill asks about the evacuation of Earth and if this is the last remnant of humans, and the Doctor says many ships were sent out and that he'd encountered a few before, and yet later, the Doctor is screaming about saving these people, because if he doesn't, then the human race would be extinct.
Fair point. I'd say it wasn't the only place, because seriously, if the Doctor was that close to committing genocide again and there was no further comment on it, it'd be ridiculous.