Lobos said:
Does anyone know if civilizational theory is a thing? In other words, creating solutions for how large populations can prosper in a particular structure.
Or would that be a philosophy of some kind?
It's not clear what you mean by "creating solutions for how large populations can prosper in a particular structure."
The study of civilizations, or more broadly, "cultures", falls under anthropology:
http://en.wikipedia.org/wiki/Anthropology
In general, civilizations are not built ready made in one fell-swoop, but evolve over time. If a civilization grows too large or too complex for its population to continue to thrive, then, over time or all of a sudden, that civilization will begin to decline, until it is either replaced with something more tractable for people to thrive, it is absorbed into a rival culture, which functions more efficiently, or it disappears altogether, as a result of some natural or man-made catastrophe, like being conquered or having a volcano blow up.
One of the best known early works on the study of civilizations is, of course, Gibbon's
Decline and Fall of the Roman Empire (1776).
A popular author of more recent vintage is Jared Diamond:
http://en.wikipedia.org/wiki/Jared_Diamond
Several of his books have studied why various cultures (including our own) thrive and why others fail abjectly, in spite of apparently having a wealth of resources on which to draw.