Importance of soure availability and accessibility: a case study from Papua New Guinea

The study of ancient trade and exchange would benefit from detailed analyses conducted at the level of the individual obsidian exposures. A useful method is to evaluate the null hypothesis thai all potential sources were equally favourable to those who exploited, exchanged, and used the obsidian Before deviations from the null hypothesis can be inferred as social behaviour, the physical characteristics of the obsidian exposures and their history in time and space should he studied. These points are illustrated by a case study from Papua New Guinea where volcanic activity during the time of occupa tion radically altered the availability and accessibility of obsidian sources. Having accounted for environmental factors, changes in the abundance of obsidian from various chemical groups is interpreted in terms of a highly flexible system of exchange that may have been adopted lo help cope with the high risks created by volcanic activity.