The collapse of the civilization that once spanned the world marks the end of the old world and the beginning of the Fifth World.
Oral histories across the Fifth World cite many reasons why civilization came to an end. Ecological collapse, financial collapse, terrorism, war, new epidemics, the depletion of fossil fuels, and political turmoil and unrest appear most often. They all played their part, and yet none of them can adequately explain why civilization failed. After all, we build civilizations expressly to deal with crises like these. If a civilization fails to do so, we must ask why this particular civilization failed to meet this particular challenge.
Like all other civilizations before it, the global civilization that preceded the Fifth World collapsed, ultimately, because complexity remains subject to diminishing marginal returns. A society’s first investments in complexity often offer significant gains for relatively little input. Later on it takes more and more time, effort, and/or resources to continue increasing society’s complexity, even though it offers relatively less in return. The space program offered many benefits on earth, but not nearly as much as the invention of fire, even though spacecraft require far greater investments than bow drills.
At some point along this curve, the members of a complex society begin to wonder if they might not enjoy all the benefits that their current society affords at a lower cost by simply living more simply. Collapse unfolds as an economizing process, initiated precisely at the moment when most people would benefit from it.
Civilization did not collapse everywhere or all at once. It showed itself first in growing discontent and economic hardship. Recessions became deeper, more frequent, and longer-lasting. In between, the economy would recover, but each time less fully than the last, and each time would see the gains of that recovery more and more unequally distributed, with the divide between rich and poor growing.
The basic necessities of life — food, water, and shelter — became increasingly expensive, and increasingly beyond the reach of the poor. Such desperation led to rising political tension, and eventually to violent clashes, first in the form of crime and violent political protests, but then in more pitched confrontations. As always nation-states failed to meet the needs of their people, smaller, more local organizations, from charities to churches to street gangs, tried to fill that void, eventually claiming greater allegiance and identity. At no point did any of the old nation-states declare themselves dissolved, of course. They simply became irrelevant, often sinking deeper and deeper into authoritarianism and fascism, even as their power waned to little more than city-states.
In the areas where civilization brought prosperity, like Europe and North America, many remember the collapse of civilization as a terrible ordeal with names like the Great Purification or the Apocalypse. Other parts of the world reserve names like those for the era preceding it, when those richer areas exploited them. In those parts of the world, the basic necessities had become forbiddingly expensive long before. They had, of necessity, developed means of surviving. The collapse of civilization did not leave them unaffected, but its difficulties often seemed in line with the difficulties they had already become accustomed to. For example, one country might lose its food shipments, but at the same time the meddling international bank that had required them to plant cash crops instead of food became powerless to dictate terms to them any more, such that their difficulties overall did not change dramatically. Navigating the rapidly-changing situation posed a distinct challenge, of course, but not an impossible one.
The era of collapse gave way to a period often called the Rusting Age.