http://europe.theoildrum.com/node/5528
An interesting (if long) article comparing the fall of Rome to other civilizations, including our own. He quotes Marcus Aurelius, “Nature which governs the whole will soon change all things which thou seest, and out of their substance will make other things, and again other things from the substance of them, in order that the world may be ever new.”
Or, as Heraclitus put it, more succinctly, “the only constant is change.”