Impact of early Polynesian occupation on the land snail fauna of Henderson Island, Pitcairn group (South Pacific)

Henderson Island, an uninhabited raised coral atoll in the Pitcairn group, has recently been designated a World Heritage Site because of its unique and relatively undisturbed ecosystem. The island is believed to have been uplifted and subaerially exposed during the last 275 kyr. This therefore provides the maximum age for the terrestrial biota that includes several endemic taxa. Henderson today supports 16 strictly terrestrial species of snails, about half of which are endemic. Analyses of sediments beneath Polynesian occupation horizons dated between the 11th and 17th centuries AD, have yielded 11 species of land snail present in the modern fauna, together with at least six (and possibly as many as eight) further species that no longer occur on the island. These extinct taxa are illustrated and formal descriptions provided for five (Pleuropoma hendersoni, Orobophana carinacosta, Minidonta macromphalus, Philonesia pyramidalis, P. weisleri); a sixth, known only from broken shells, appears to belong to the genus Hiona. The two remaining taxa are 'tornatellinids' that have not been recognized among the modern fauna. Radiocarbon dates from bones of associated extinct land birds confirm their occurrence on Henderson before the first signs of Polynesian settlement. The extinction of these taxa seems to coincide with the Polynesian occupation and evidence for large-scale burning, at least around parts of the plateau margin, suggests that their demise can be linked with habitat destruction. At least three species, Gastrocopta pediculus, Lamellidea oblonga and Pupisoma orcula, first appear in Polynesian occupation horizons. Their status as prehistoric introductions is therefore confirmed but G. pediculus no longer lives on Henderson. Pacificella variabilis, Tornatellides oblongus parvulus and Elasmias sp., all previously thought to have been other prehistoric introductions to Henderson, were recovered from pre-Polynesian levels and are therefore native

Advances in Polynesian prehistory: A review and assessment of the past decade (1993-2004)

The pace of archaeological research in Polynesia has intensified in recent years, resulting in more than 500 new literature citations over the past decade. Fieldwork has continued in such previously well-studied archipelagoes as Tonga and Samoa in Western Polynesia, and Hawai'i and New Zealand in Eastern Polynesia, and has expanded into previously neglected islands including Niue, the Equatorial Islands, the Austral Islands, and Mangareva. The emergence of Ancestral Polynesian culture out of its Eastern Lapita predecessor is increasingly well understood, and the chronology of Polynesian dispersal and expansion into Eastern Polynesia has engaged several researchers. Aside from these fundamental issues of origins and chronology, major research themes over the past decade include (1) defining the nature, extent, and timing of long-distance interaction spheres, particularly in Eastern Polynesia; (2) the impacts of human colonization and settlement on island ecosystems; (3) variation in Polynesian economic systems and their transformations over time; and (4) sociopolitical change, especially as viewed through the lens of household or microscale archaeology. Also noteworthy is the rapidly evolving nature of interactions between archaeologists and native communities, a critical aspect of archaeological practice in the region

Inferring population histories using cultural data

The question as to whether cultures evolve in a manner analogous to that of genetic evolution can be addressed by attempting to reconstruct population histories using cultural data. As others have argued, this can only succeed if cultures are isolated enough to maintain and pass on a central core of traditions that can be modified over time. In this study we used a set of cultural data (canoe design traits from Polynesia) to look for the kinds of patterns and relationships normally found in population genetic studies. After developing new techniques to accommodate the peculiarities of cultural data, we were able to infer an ancestral region (Fiji) and a sequence of cultural origins for these Polynesian societies. In addition, we found evidence of cultural exchange, migration and a serial founder effect. Results were stronger when analyses were based on functional traits (presumably subject to natural selection and convergence) rather than symbolic or stylistic traits (probably subject to cultural selection for rapid divergence). These patterns strongly suggest that cultural evolution, while clearly affected by cultural exchange, is also subject to some of the same processes and constraints as genetic evolution