Pollution a Sign of Intelligence ?

This article has me cracking up ! So , a green and verdant world must be inhabited by stupid aliens ? I hope you all see the humor here !

http://www.npr.org/blogs/thetwo-way/2014/08/22/342448208/scientists-searching-for-alien-air-pollution

I think there is humor to that article, though I think pollution is more of a sign of mildly advanced civilizations. I think they were looking for aliens equal to our civilization's advancement, not greater. As I view it, I think civilization and intelligence (looking at humans) follows a parabolic curve or sine/cosine wave: at first, there is no to minimal pollution, half-way there is a lot of pollution until a threshold level is reached where everyone is faced with the choice of changing ideas and advancing, and then, the civilization either dies back completely, goes back to phase one, or makes the necessary changes and advances.

Kinda like this movie: The Day the Earth Stood Still

If I remember correctly, I think there is more dark matter and dark energy in the universe than the matter and energy we see and use. Therefore, I think advanced civilizations and evolved organisms display their intelligence and usefulness through energy/material efficiency. Likewise, I find it to be self-evident in nature that only the most efficient organisms survive, because there is only so much to go around that wastefulness could result in extinction.