Marxism
Marxists think that all of written human history has been divided by economic classes. One example is feudal society (a medieval society controlled by feudal lords and nobles). The ruling class got their power and wealth from the labor of peasants (farmers). But as peasants demanded more and more for themselves, small shopkeepers and tradespeople began to appear. Many of these people formed guilds and eventually began to employ workers.  These workers were able to gain wealth for themselves at these jobs. These historical events created capitalism.