The external manifestations of ancient trading networks have generally been of greater scholarly concern than the internal needs and systems of the societies which created and participated in them. Both aspects of commercial relations are, however, inextricably linked. Preliminary research supports the idea that much of the movement of luxury goods in Southwest Asia during the third millennium B.C. was generated in response to the specific and unique demands of Sumerian society, and that such commercial enterprises continued under the Akkadian rulers. This hypothesis can be used to explain the distribution of certain metals in the third millennium, notably tin and silver. The sources of the tin used in ancient Southwest Asia have, despite considerable research, remained a mystery for years (see most recently Muhly 1985).
Following is a speculative attempt, using archaeological and scientific evidence, to explain the reasons why tin bronze is of limited distribution in Southwest Asia and the eastern Mediterranean during the third millennium. Tin bronze occurs in third millennium contexts in Mesopotamia, the Troad, and central Anatolia, and rarely elsewhere until late in the millennium. Such a pattern of distribution might be explained by the presence of tin deposits in each of these areas, exploited to fill only local needs, but geological research has failed to detect tin ores in any of these places. Since some source of tin was clearly being exploited to supply these areas and because there seems to have been differential access to it, geological presence or absence of tin must not have been a determinative factor. An alternative explanation is here developed by examining the nature of the tin trade and of the entities involved in it.