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 (Marxism) of value, product-values in an open market are regulated by the average socially necessary labour time required to produce them, and price relativities of products are ultimately governed by the law of value. Commodity-trade, Marx argues, historically begins at the boundaries of separate economic communities based otherwise on a "non-commercial" form of production. Thus, producers trade in those goods of which those producers, have episodic or permanent surpluses to their own requirements, and they aim to obtain different goods with an equal value in return. Marx refers to this as "simple exchange" which implies what Frederick Engels calls "simple commodity