Research Highlight - Professor Glenn Summerhayes

 
The signature of identity: obsidian exchange in late Lapita Society of the western Pacific as an indicator for regional breakdown and the beginnings of local identity
 

Identifying and quantifying where the obsdian found in archaeological sites originated from is important in identifying ancient trade and exchange patterns and modelling the social and economic nature of prehistoric societies from the western Pacific. In this study, PIXE-PIGME was used characterise and source obsidian found from sites on the island of Watom, East New Britain, Pappua New Guinea, dated from 3,000 to 1600 years ago. This period of time is crucial in understanding changes to Lapita society and its subsequent transformation. To model chronological differences in source selection 89 flakes of obsidian was sourced from the sites of Kainapirina (SAC), Vunaburigai (SAB), Vunavaung (SDI) and Vunatambun (SDI) which were excavated by Dr. Dimitri Anson on Watom in 2008-09. Any shift of the relative proportion of the major obsidian sources are taken as indicators of changing exchange relationship and changing “social distance” between Lapita communities.
 
The overall results confirms the regional pattern of obsidian source selections where the West New Britain obsidian sources round Talasea were the predominant utilised sources at Watom throughout the sequence, with the relative proportion of them increasing over time. In comparison, obsidian from the Admiralty Islands composed only a small, although in some sites a significant portion of the assemblage. Of importance is identification of obsidian at SDI layer 4 from the Mopir source which had been covered and made inaccessible by the devastating volcanic eruption of nearby Mt Witori dated to 3400 years ago. The re-emergence of Mopir obsidian informs us of opening of social ties with exchange partners to the west and its increase over time may be related the development of a more or less down the line exchange pattern. To sum up, the intra-site study of the chronological differences in obsidian source selections at Watom are providing new insights to the understanding of local Lapita sequences and its successors.
 
Professor Summerhayes is an expert on the archaeology of New Guinea and has been working with AINSE in solving archaeological problems for the last 30 years. He is currently based in the Department of Anthropology & Archaeology at the University of Otago. Ms Elaine Chen is a student of Prof Summerhayes at Otago, has just submitted her MA dissertation on the obsidian from Watom. Dr Dimitri Anson, a Visiting Fellow at Otago, undertook excavations at Watom over a twenty five year period.