I made a friend twitch by asking him what the post-technological world would be like. So, wide-open question: What comes after technology for the human race? Sociological implications? Psychological implications? Will we be Markovians? Angels? House plants?
The idea that we would hit random planets with those things and destroy the extant ecology for our own purposes without considering if there are living beings there is horrifying. And very human.
We find residences nearly that old, Sterkfontein comes to mind immediately. But the technology didn't exist to building structures more complicated than wickiups until we got together to make civilizations.
The lunatic fringe will claim otherwise, of course.
Have we searched every galaxy in the Universe?
Are those two criteria the only ones that would provide signs of intelligent life?
Does the intelligent life have to be farther along technologically than we are?
If they are truly intelligent and out there why would they contact us?