During this Dark Age, the Greeks, living on a rocky peninsula where large-scale agriculture was impossible, invented a new economic system based on olive oil, which was almost the petroleum of the ancient world. They sent out colonies to Anatolia and all around the Black Sea, as well as to Italy, all of which grew olives and exported olive oil. By about 800 B.C., a new, non-aristocratic merchant class dominated Greek-speaking society, and it was their pragmatism and relative freedom from the ˘dead hand of the past÷ that apparently enabled them to think new thoughts and begin to develop philosophy. It is said that Thales, considered the first philosopher, was in the import-export business, invented the concept of the mathematical proof in order not to be short-changed in overseas transactions, and began thinking up naturalistic explanations for such phenomena as eclipses and fossils.
Greek culture evolved a system of independent city states that were usually at war with one another, and despite Athenian culture and political dominance, Athens was overthrown by the conservative and militaristic Spartans, and never regained its former dominance. Greece and much of the rest of the known world was first unified under the short-lived empire created by Alexander of Macedon, but then fell apart into six different provinces ruled by his generals. The Mediterranean world was not permanently unified until it was all conqu