What challenges do civilization go through as they build their empire?

Cities were at the center of all early civilizations. People from surrounding areas came to cities to live, work, and trade. This meant that large populations of individuals who did not know each other lived and interacted with one another. So, shared institutions, such as government, religion, and language helped create a sense of unity and also led to more specialized roles, such as bureaucrats, priests, and scribes.

Explanation:

Today, almost every city has a supermarket with a wide variety of available foods. We take for granted the fact that people have different types of jobs and that governments exist. But, reliable food sources, specialized work, and governments did not exist for most of human history! They are the products of historical processes that began with the first civilizations several thousand years ago.

A civilization is a complex society that creates agricultural surpluses, allowing for specialized labor, social hierarchy, and the establishment of cities. Developments such as writing, complex religious systems, monumental architecture, and centralized political power have been suggested as identifying markers of civilization, as well. When we see these changes occur, we should stop and ask, “Did people institute these practices because they were beneficial, or were they forced on them?” Historians debate this very question, trying to determine whether civilization was a bottom-up or top-down development.^1  

Some people think civilization is an advanced stage in the progression of human cultural evolution. But, when historians or anthropologists use the term civilization, they mean a society has many different, interconnected parts. So, rather than thinking about different forms of social organization as completely separate models, it’s helpful to think in terms of a spectrum of complexity. On one end, we have hunter-forager societies—which have little complexity—and on the other end, we have civilizations—which are highly complex. In between lie a wide variety of social structures of varying types and levels of complexity.

crop rotation kepy different plants in the soil instead of once constintly. when switching out plants you have different nutrients being absorbed at different speeds and different roots growing differently therfore the spoil and water flow have to adapt and carry fresh nutrients to carry the constant changes that were going on in the soil.