Indeterminacy and approximation in Mediterranean weight systems in the third and second millennia BC

Research on weight systems used during the Bronze Age, prior to the introduction of writing, generally assumes that the widespread use of metal as ‘commodity currency’ eventually resulted in the adoption of widely shared systems of measurement. Many studies aimed at the identification of recurrent weight values as multiples and/or submultiples of theoretical standard units. This approach faces two limitations: 1) the absence of written sources, or at least statistically sound samples, makes it difficult to either validate or reject any reconstruction of prehistoric systems; 2) in the literate Ancient World, different polities usually retained distinct systems. Here an alternative analytical framework is outlined, making use of elementary statistics and crosshistorical comparisons, and relying positively on ‘indeterminacy’ and ‘approximation’ rather than on ‘exactness’. Recurrent weight measures can correspond to ‘Standard Average Quantities’, rather than representing arrays of exact multiples/submultiples of given units. By departing from a ‘fractional’ theoretical logic, one can observe that constant exchange practice may have produced the normalisation of ‘tradable quantities’ and that this can happen without necessarily implying the unification of local systems.