Morphometric analyses of Batissa violacea shells from Emo (OAC), Gulf Province, Papua New Guinea

Abstract

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.

Life on the Margins : An Archaeological Investigation of Late Holocene Economic Variability, Blue Mud Bay, Northern Australia

“…Swadling 1976Swadling , 1977Botkin 1980;Spennemann 1987;Yesner 1988;Jerardino 1997;Lightfoot and Cerrato 1998;Bourke 2000Bourke , 2002Peacock 2000;omas 2001, 2002;Bailey and Craighead 2003;Masse et al 2006;Braje et al 2007;Milner et al 2007;Antczak et al 2008;Baez and Jackson 2008;Erlandson et al 2008;Morrison and Cochrane 2008;Nielsen 2008;Parkington 2008;Peacock and Mistak 2008;Rick et al 2008;Whitaker 2008;Yamazaki and Oda 2009;Giovas et al 2010;angavelu et al 2011). In many of these studies, a reduction in average shell size and changes in the relative abundance of higher-ranked resources in the archaeological record are viewed as indicating increased pressure via human or environmental factors (e.g.…”

“…Spennemann 1987:85, 89;Claassen 1998:108;Bailey and Craighead 2003:187). e use of only complete shells for metrical analyses has the potential to introduce bias into the sample via di erential patterns of fragmentation relative to size angavelu et al 2011). In order to investigate changes in size throughout the A. granosa dominated deposits, therefore, complete and fragmented valves were measured and reconstructive morphometric equations (as outlined in Faulkner 2010) applied to the fragmentary valves for the establishment of full lengths (Figure 6.5).…”

Kumukumu 1, a hilltop site in the Aird Hills: Implications for occupational trends and dynamics in the Kikori River delta, south coast of Papua New Guinea

“…For it is clear that sustained occupation of Emo placed local protein resources under significant exploitative pressure. Residents of Emo were forced to consume smaller shellfish than their ancestors who had lived at the same site (Thangavelu et al, 2011), and wild game appears to have been relatively scarce, at least in proximity to the village. On the other hand, a stable residential base may have allowed for the mounting of hunting expeditions to more remote sites by groups of individuals, and for family groups to spend time away from the relative safety of a larger village to occupy more temporary (kombati) camps at which they could produce the all-important sago and to incidentally hunt, fish and gather other wild resources.…”

“…This hill backs and rises steeply northwest of Emo, the location of an ancient river-bordering village that includes the archaeological site of that name (PNG National Museum and Art Gallery site OAC, previously reported as the 'Samoa' site named after an early-twentieth century missionary village populated mainly by Kerewo) (cf. Rhoads, 1983;David et al, 2010;Thangavelu et al, 2011). Excavations at Emo revealed a sequence of four shortlived occupational phases dated to 1780 cal BP, 1560 cal BP, 1470 cal BP and 660 cal BP (David et al, 2010).…”

“…Excavations at Emo revealed a sequence of four shortlived occupational phases dated to 1780 cal BP, 1560 cal BP, 1470 cal BP and 660 cal BP (David et al, 2010). Morphometric analyses of the 18,096 measurable Batissa violacea shells from Emo, representing 87% of a total MNI of 20,911 excavated shells of that species, revealed evidence of rapid predation pressures on shellfish at the start of each occupation phase, indicating site abandonment and a shift to the exploitation of more distant resource locations in the intervening periods (Thangavelu et al, 2011). These patterns were interpreted as signalling settlement and subsistence responses to fluctuating headhunting raids (site abandonment) and active ancestral hiri trade partnerships (site re-establishment) during the last two millennia, a situation reminiscent of ethnographically documented patterns.…”