[Bube]

Ok, so think about this:

Remember when Daniel told Desmond the coordinates (or something) back in the 4th season, and wanted him to pass it on to the past-Daniel? Then Daniel uses those coordinates to come to the island. But how could he have learned the coordinates without ever going to the island in the first place? And how could he have got to the island without knowing the coordinates?

And there was also something about the rat in Dan's lab as well, but can't remember it right now..

Time travel sucks.