Stable isotope studies applied to skeletal remains of early
Stable isotope studies, applied to skeletal remains of early Pacific populations, have shown a trend toward a horticultural diet with temporal variation in response to local environmental conditions (Field et al., 2009; Kinaston and Buckley, 2013; Valentin et al., 2010, Valentin et al., 2014; Kinaston et al., 2014, Kinaston et al., 2015, Kinaston et al., 2016). As a consequence, human groups associated with the late-Lapita/immediately post-Lapita SP2509 are expected to have stable isotope ratios indicating that fewer marine resources were consumed compared with the first Lapita colonizers. We expect that post-colonization groups should have: (1) lower collagen stable carbon and nitrogen isotope ratios suggesting a higher terrestrial animal intake; (2) lower apatite stable carbon isotope ratios indicating an increased reliance on food items with a higher carbohydrate content such as taro and other cultivated plants and, (3) a lower dispersion of collagen and apatite stable isotope ratios reflecting adoption of a dietary standard based on terrestrial resources. These assumptions are examined here through multiple stable isotope analyses, including results from new human collagen and apatite bone samples (n = 21) obtained on early Polynesians people from the Talasiu site (Kingdom of Tonga) and their comparison with isotope results from other parts of the Pacific.
Talasiu site The Talasiu site (TO-Mu-2) is located on the palaeoreef-limestone shoreline of the Fanga ‘Uta Lagoon, north of Lapaha Village, only 2.5 km south of Nukuleka Village which is regarded as the place of the initial Lapita landfall in Tonga (Burley et al., 2010) (Fig. 1). The site consists of a dense shell midden deposit ~90 cm thick covering some 450 square meters. This midden contains large numbers of bivalves, mixed with pot sherds, charcoal, bone, and shell and stone artifacts, but no fishing gear except perhaps for tiger cowrie caps (Cypraea tigris) that have been considered parts of a composite octopus lure rig (Poulsen, 1987, for a critical discussion of these artifacts see Spennemann, 1993; Best, 1984: 459), and perforated Anadara sp. shells that are sometimes thought to be net weights (but see Connaughton et al., 2010). The pottery is predominantly plain with some dentate-stamped vessels bearing simple open designs typical of late Lapita ceramics. Shell artifacts include short and long shell units, broad Conus spp. rings, narrow rings made of Conus spp. and Tridacna spp., and small circular flat beads that are similar to Lapita ornaments. Lithics items comprise adzes, flakes, grinding stones and oven stones whose raw material has a distinct geographical source with obsidian from northern Tonga and lithics from ‘Eua (south Tonga), Samoa, east Fiji and volcanic islands within Tonga, suggesting significant population mobility (Reepmeyer et al., 2012; Clark et al., 2014). The deposit also includes features, such as ‘hearths, ovens, oven rake outs, and burials, placed at the base of the deposit or interstratified within the midden. The 95% probability range of radiocarbon determinations obtained on coconut endocarp, unidentified charcoal, worked shell grave goods and human bone samples fall between 2750 and 2150 cal. BP (Valentin and Clark, 2013; Clark et al., 2015; Skoglund et al., 2016) (Table 1). Calibrated charcoal and bone 14C ages between 2600 and 2300 BP are strongly influenced by curve flattening resulting in multiple curve intercepts and a substantial widening in the calibrated age range of determinations. However, a high-resolution chronology based on Uranium-Thorium (U-Th) dating of coral files and Accelerator Mass Spectrometry (AMS) dating on short-lived material demonstrates the Lapita period on Tongatapu spanned 2850–2650 cal. BP (64.2% prob) (Burley et al., 2015) and it is highly likely that the midden and burials at Talasiu date to ~2700–2600 cal. BP and are of late Lapita/immediately post-Lapita age.