Final answer:
Cultural evolutionism theorizes that societies evolve from simple to complex stages, as seen in ancient Mesopotamia, which developed from hunting and gathering to a complex agricultural civilization with governance, writing, and architecture.
Step-by-step explanation:
One of the theories about why and how complex societies arose is cultural evolutionism, which was influenced by the work of Charles Darwin on biological evolution. This theory, advocated by 19th-century anthropologists like Edward Tylor and Lewis Henry Morgan, posits that human cultures evolved from simple to more complex forms over time. Tylor distinguished between savagery, barbarism, and civilization, linking these stages to technological advancement and modes of subsistence like hunting and gathering, farming, and finally the development of states with more advanced forms of trade and government.
An example of a culture that fits this theory is ancient Mesopotamia, which emerged along the Tigris and Euphrates rivers. This society transitioned from nomadic hunter-gatherer groups to an agriculturally sustained population, which led to the development of complex social structures, governments, writing systems, and significant architectural accomplishments like the famous ziggurats.
However, the concept of unilineal cultural evolution has been largely abandoned, as anthropologists like Franz Boas have argued that cultures evolve according to their own unique histories and in constant interaction with one another.