Of course, the opposite of the "aliens just stayed home" hypothesis is the hypothesis that we're the first species in the universe to acquire technology, and th

Of course, the opposite of the "aliens just stayed home" hypothesis is the hypothesis that we're the first species in the universe to acquire technology, and that we'll spread throughout it within a few more decades, eliminating any possibility for any other species to do the same. Personally I doubt it's possible to exceed the speed of light. I think it's more likely that we'll slowly spread throughout the Milky Way, and that while simple life and complex-but-unintelligent life are likely to be pretty common, the average distribution of technological species is probably something on the order of one per galaxy. Just a hunch.