How Do You Define Money?

From Mesopotamian loan records which are over 4,000 years old to the cryptocurrencies of today, money has been with us for a long time. But how did we get from exchanging bits of metal or cowrie shells to the algorithmic trading of shares? Why did paper money originate in Song-dynasty China? Why was the Gold Standard adopted in the 19th Century? And what is money anyway? These are some of the questions that Bridget Kendall investigates with the help of three financial historians: Ute Wartenberg, president of the American Numismatic Society; William Goetzmann, professor of Finance and Management Studies at Yale University; and Christian de Pee, professor of History at the University of Michigan. They also answer listeners' questions about the history of finance.

(Photo: Roman gold coins found in Corbridge, UK in 1911. Credit: Universal History Archive/Universal Images Group/Getty Images)