I remember that when I was reading "The boat of a million years" there was a description on the different types of civilization taking into account how the civilization was able to use the resources of the planet, galaxy, etc. Now I know this is based on the so called Kardashev Scale and that even Carl Sagan calculated where we, humans, are: in our infancy. We still don't know how to get the best use of the resources from our planet Earth.
Are there others there? If any of those civilizations is far more advanced than us, why haven't we heard from them?
I suggest you enjoy the reading in UFO Evidence HERE and HERE and, for a very complete and exhaustive summary, just click on the picture below.
What do YOU think??