Interesting video on money, quite a different take than I hear from bitcoiners: https://www.youtube.com/watch?v=X-D5FERQzU4

My summary of the video: There were never any barter economies. Money predates writing (the oldest writing cuniform on clay tablets were accounting records). Money is always tightly tied up with state power, primarily because states can enforce payment for debts owned which originated from people accidently harming other people.. the governmental power steps in and says "A owes B X amount of state-approved money to make this right." Thus, the value of a currency without intrinsic value is imparted to it by the power of the state that controls that money. Taxes just tie it even tighter to the governmental power. Every central power (state) has it's own money, with few exceptions (e.g. the Euro experiment, which is failing).