In educating business students on the ways of the commercial activity awaiting them after graduation, I have illustrated the barter system as broken down to essentially consist of Exchange and Communication, or in more modern terms, the Economy and Media. Once you know what you are here to contribute, it is your job to professionally offer it, and publicly communicate that you are available for this product or service. 

What was once sustainable as the direct trading of goods between ancient populations, has required the medium of exchange we call money, since pre Pythagoras 430-450 BC (6). Marketing over mass media of communication appeared in China circa 1040 AD with “Movable Type,” and was reinvented by Johannes Gutenberg in Europe around 1440 in what led to introduce the printing press (7).