If you go back to having 10 civilizations in the Milky Way, and yet somehow by this thoery you expect 1 of them to have passed through here, I have this to say:
1. You are far too hopeful, this is a big place, and we're on the edge
2. If they have gotten this far (look how long it took man to sail into the unknown) would we really see them?
3. Nature has an amazing way of adapting, who says our little planet here is habitable to those other 10 civilizations? (They might be alergic to water like in "signs", which btw is freaking stupid, if they have the knowledge to get here and invade, don't you think they'd realize thier death comes from the sky randomly and the planet itself is 70% kill them material)
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