According to Guns, Germs, and Steel, how does society change over time?
Diamond breaks human societies down into four basic groups: Band, Tribe, Chiefdom, State. This allows for variations on societal norms, and the eventual creation of the "kleptocracy," where the rulers deliberately exploit their workers for personal gain.
Bands tend to be nomadic, moving around as the environment and other factors change. This society is based in survival, and puts little time and effort into political maneuvering.
Tribes are the first fixed society, and as their population increases they begin the steps necessary to create a top-down, class-oriented society. However, their day-to-day life is still based in hunting/gathering and survival, and so political issues are relegated to clan or territory disputes.
Chiefdoms are the first explicitly kleptocratic societies; the chief and his men rule over the lower class, claiming a portion of their work as "owed" and organizing rules and laws. Chiefdoms as they existed in history are extinct; they were too numerous and powerful for European society to ignore, and so they were wiped out by advancing "civilization."
States are the current mode of society; a group of people, united by a common religion, heritage, or landmass isolation form a government body and use it to rule over workers. Despite the claims of equality, even democratic and representative governments are kleptocracies; the government takes an undue share of the working-class's production, ostensibly for the upkeep of government or protection of the people, but more often for personal enrichment.