The following few paragraphs from an article in ZDnet I thought were quite interesting:
Consider the theories of David Keys, an archaeology correspondent for the London daily, The Independent. To demonstrate the inherent weaknesses that lie within a structure with too many internal interdependencies, he chronicled a turbulent period within the middle of the first millennium, in which a series of climatic calamities and pandemics brought down every major established civilization within a century’s time. The era’s most modern societies had become too complex to adjust to the changes around them. Yet, their less sophisticated rivals thrived. Simplicity dramatically won out over complexity in a high stakes battle for survival.