Advanced alien civilizations, have we already found some?

Lots of scientists think our Galaxy should be full of advanced alien civilizations (see the Drake Equation and Fermi Paradox posts). But when they’ve looked the Galaxy appears to be quiet and lonely. Where are all the alien civilizations they ask?

Many insane people would of course argue with this, pointing out that aliens have visited us; that they created the pyramids, Atlantis and humankind itself. That they regularly abduct and probe drunk Americans, that the government knows and is covering it up, and that the government itself may even by aliens, alien communists, sent here to steal freedom from God-loving Americans. But then they’re insane. None of this is true.

In a previous post I argued that alien life might be common, but that simple life rarely evolves into intelligent life, and that even if it does, intelligent life may not exist for very long. However I may be wrong, I’m wrong about things all the time, especially as some astronomers may have discovered evidence for vast alien structures in space, I shit you not.