Outstanding article on the history of money, and how Bitcoin is the obvious organic evolution of payment systems.. Well worth your time to read.
A long time ago on the island of Yap in Micronesia people used stones as money. Back then some African communities used sea shells as money, people in Asia used salt as money, and people in North America used beads as money, but on the island of Yap, you used stones as a way of saving, making payments and keeping track of prices. A lot of small stones would get you a really big stone; some were the size of an elephant and weighed more than 8,000 pounds. Obviously, you didn’t take the big stones home – you left them where they lay – but everyone knew the big stone was yours.
The people of Yap knew that stones did not need to be valuable to be useful. The stones became valuable precisely because they served as an effective way to save, pay, and price things.