The Greek civilization originated in the Balkan Peninsula in the 8th century BC. They lived in independent city-states called polis, with Athens and Sparta being two important ones. Polis were initially governed by aristocracies but some later transitioned to democracies. Due to overpopulation, many Greeks migrated and founded colonies around the Mediterranean, spreading Greek culture. Greek society was divided between citizens, who had rights, and non-citizens like foreigners, slaves, and women who had few to no rights. The Greeks made important contributions to philosophy, science, theatre, and architecture.