[wongarsu]

I don't think it says anything that no aliens destroyed us yet. If such aliens would exist and such an event would have taken place in our solar system, that would still have been a long time ago. I don't think it's fair to assume that that alien race would just go around and kill all planet with live like a child stamping on ants.

It would be far more likely that they would be at least as sophisticated as humans, with emotional and strategic reasons, complex governments that change every now and then etc. By now they would probably be entirely different people from back then, just as our ethics evolve and and human empires rise and fall over a few centuries.

I don't think it's a very likely theory, but I don't see a general problem with it.