That's my opinion too, thanks for saying it so concisely .I'm with the theory that it's almost statistically impossible for there not to be life elsewhere, and probably lots of it! I don't think there's any evidence that we've been visited though.
The South American tribes, especially---North Anerican tribes tended to be more nomadic and built less infrastructure---had a really impressive civilization going. It would be interesting to know how different things would be now if they hadn't all died out. Too bad we don't have an an Alternate Reality machine so we could see that!But the reality is that many indigenous populations had advanced cities and technology while Europe was experiencing the dark ages.