The Origins of Money
Local but extremely valuable trade was, this essay argues, made possible among many cultures by the advent of collectibles, by the time of the Upper Paleolithic. Collectibles substituted for otherwise necessary but non-existent trusting long term relationships. If there had existed a high degree of sustained interaction and trust between tribes, or individuals of different tribes, so that they gave each other unsecured credit, this would have stimulated time-lagged barter trade. However, such a high degree of trust then is highly implausible
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