I found this poster on the internet the other day. If human beings were to revert to a primalistic state or go extinct completely it would take over 200,000 years for all traces of human civilization to disappear. (It would take over two million years for nuclear waste to lose its potency, but everything else would take about 200,000 years.) That just makes me so impressed and proud of our species. No matter what happens to us as creatures the world will have no choice but to remember us for eons. And that's not to mention the satellites we have in space that are safe from degredation in the embrace of a vacuum! Here's the poster: