Academic journal article Archaeology in Oceania

Morphometric Analyses of Batissa Violacea Shells from Emo (OAC), Gulf Province, Papua New Guinea

Academic journal article Archaeology in Oceania

Morphometric Analyses of Batissa Violacea Shells from Emo (OAC), Gulf Province, Papua New Guinea

Article excerpt


Archaeological investigations of human predation pressures on shellfish usually rely on measurements of complete shell specimens. However, most archaeological shell assemblages consist predominantly of broken shells, limiting measurable sample sizes, and thus potentially biasing results in cases where shell fragmentation is biased towards particular size classes (due to shell size--fragility correspondences). This paper presents a recent application of morphometric analyses on the Batissa violacea assemblage from Emo, an early ceramic site from the Gulf Province, Papua New Guinea. Our method enabled most shell valves, fragmented or not, to be accurately and comparably measured for size. The results reveal a close match between the commencement of occupation and maximum shell sizes in a sequence of occupational phases, each separated by many decades to hundreds of years of site abandonment. While each occupational phase begins with peak mean shell sizes, the later peaks never again attain the mean shell size of the initial phase. As each phase progresses, shell sizes diminish until abandonment, and then the same pattern starts again with the next phase. Identical trends were obtained from two separate excavation squares. We interpret these results to indicate that while people may have abandoned the site of Emo between the occupational phases, they did not abandon the region, continuing to exploit local shellfish beds, albeit less frequently than during the site's occupation. These results highlight the ability of local (site-specific) archaeological shell data to shed light on regional demographic and occupational trends.

Keywords: Batissa violacea, morphometric analysis, Papua New Guinea, predation pressures, shellfish exploitation


In 2008, excavations were undertaken at the archaeological site of Emo, (also known as 'Samoa' or site OAC), situated in the Aird Hills, Gulf Province, Papua New Guinea (PNG) (David et al. 2010) (Figures 1 and 2). The site is located on flat ground, 30m west of the Komo River, 15m above high tide mark. Previous archaeological excavations at Emo were conducted by Bowdler in 1971 and subsequently by Rhoads in 1976 (Rhoads 1983). These excavations unearthed ancient pottery, the apparent antiquity of which would make it amongst the oldest dated ceramics of the south coast of mainland PNG (see also Allen 1972; Bulmer 1978; McNiven et al. 2006:69-70; Rhoads 1983:99; Summerhayes and Allen 2007:102; Vanderwal 1973).


Two juxtaposed squares (A and B), each measuring 50 x 50cm, were excavated in 2008. Excavation was undertaken in Excavation Units (XUs) of average 2.4cm thickness following the stratigraphy (where observed in situ) which comprised of 24 major and sub-Stratigraphic Units (SUs) (David et al. 2010:43). Ten AMS radiocarbon dates on charcoal were obtained, four from Square A and six from Square B (David et al. 2010:44). All of the charcoal samples were in good stratigraphic order and the radiocarbon dates revealed four distinctive occupational phases with the following commencement dates:

* Phase 1:1780 cal. BP (= approximately 1840 years ago, XU33-34);

* Phase 2:1560 cal. BP (= approximately 1620 years ago, XU23-32);

* Phase 3:1470 cal. BP (= approximately 1530 years ago, XU7-22);

* Phase 4:660 cal. BP (= approximately 720 years ago, XU1-6).


However, since individual XUs cross through SUs or sub-SUs, the XUs at the start of each occupational phase contain a combination of mixed sediments and cultural material from more than one phase (David et al. 2010:44). Excavation of Squares A and B unearthed a wide range of other archaeological material that included stone artefacts, pottery, bone artefacts, hearth stones, charcoal, plant remains and vertebrate faunal remains, with non-marine shell representing the largest faunal component and general bulk of sediments at the site. …

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