Today, a history of money. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them. A bstraction is at the root of any invention. And no invention was more abstract than the idea of replacing real goods and services with a medium of exchange.
Money is the ultimate abstraction of material things.
It represents a mental leap that had to take place in stages. The first stage predated recorded history. As people from different places traded produce, they needed frames of reference to set the value of goods. They started referring all goods to such commonplace merchandise as cattle or metal. We generalized that process at least as early as 4400 years ago.