What would happen to planet earth if the human race were to suddenly disappear forever? Would ecosystems thrive? What remnants of our industrialized world would survive? What would crumble fastest? From the ruins of ancient civilizations to present day cities devastated by natural disasters, history gives us clues to these questions and many more.
The upshot of Life After People is that, with the exception of some domesticated animals, our planet would be better off without us. Waaaay better off. Like if Mother Nature sat us down for a talk and said, "listen, you're really shitting on the rest of the planet, its residents, its ecosystems, etc. and, by the way, you're killing me slowly and painfully" and the only honorable thing to do would be to jump in a rocketship to colonize Mars or commit mass suicide so everything else could live in peace.
The other interesting thing about the show is how little is left of humans after a few thousand years of absence. Roads, buildings, cars, bridges; they all break down. Ashes to ashes, dust to dust. The Great Pyramid at Giza might still be around in another ten thousand years, but it may be covered in sand. The Great Wall of China and Hoover Dam could survive for awhile longer. Mount Rushmore, caved out of solid granite, may last for 200,000 years or more. They didn't mention anything about cut & diamonds or objects made from platimun or titanium, but I imagine that they would last millions of years, if not practically forever.
Which leads you to wonder: if the Earth supported an advanced civilization that died out over 500,000 years ago, would we have any way of knowing they even existed? Small cut gemstones and platinum artifacts left behind by such a civilization would be difficult to discover unless they were of sufficient size. Fossils would certainly survive in some form and we could perhaps make some guesses as to their intelligence based on morphology. Would that be enough to detect them?
Update: Two other possible advanced civilization detectors: chemical and geological changes caused might show up in mineral layers and long-lasting nuclear waste. (thx, jordan & leonard)