Commodity market in Sumer between 4500 BC and 4000 BC. Sumerians first used clay tokens sealed in a clay vessel, then clay writing tablets to represent the amount—for example, the number of goats, to be delivered. These promises of time and date of delivery resemble futures contract. Early civilizations variously used pigs, rare seashells, or other items as commodity money. Since that time traders have sought ways to simplify and standardize trade contracts. Gold and silver markets evolved in classical civilizations. At first the precious metals were valued for their beauty and intrinsic worth and were associated with royalty. In time, they
Commodity rent, profit, labour and the costs of wear and tear on the instruments of husbandry. David Ricardo, a follower of Adam Smith, modified Smith's approach on this point by alleging that labour alone is the content of the exchange value of any good or service. While maintaining that all exchange value in commodities was derived directly from the hands of the people that made the commodity, Ricardo noted that only part of the exchange value of the commodity was paid to the worker who made the commodity. The other part of the value of this particular commodity was labour that