We watched as they destroyed themselves, had we opened our doors we would have been destroyed along with them. What they gave us by being destroyed is the key to keeping our civilization stable. Like countless other civilizations that we suspect fell in much the same way before them the signs were all there and some even suspected the end was near. Of course those who suspected are our ancestors and it is why we know so well the history of what led to the demise of the greatest civilization on Earth and why we won’t make the same mistakes.