I think we don't exist at all, it's not our future or past, just another universe.
Of course it's another universe. So is every other TV show, movie, book, short story, fantasy sports team, etc. ever created. BSG isn't "more" another universe than any of those. That's the very nature of speculative fiction.
I think we are in BSG's distant past. Kobol is a colony of Earth. All of these people are our descendants.