Prehistoric Human Impacts on Rapa, French Polynesia

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With the world's population exceeding six billion, human-induced environmental change is an acute problem confronting our increasingly inter-dependent global community. Agricultural expansion, deforestation, soil depletion, and decreasing crop yields contribute to food scarcity and world hunger (Brown 1996). In coastal and island settings, where a large percentage of the world's population resides, fisheries are being decimated at an alarming rate (Pews Ocean Commission 2003). The local effects of food scarcity, which include social fragmentation, migration, conflict, and the overall destabilisation of political systems, have far-reaching consequences and archaeologists are well positioned to provide a historical perspective on social and political responses to anthropogenic environmental change (Crumley 1994; Lentz 2000; Jackson et al. 2001; Redman et al. 2004).

Remote islands provide well-bounded microcosms for studying the ecosystem effects of human colonisation, demographic expansion, and resource intensification, along with inter-related behavioural responses promoting sociopolitical integration or fragmentation (Kirch & Hunt 1997; Kirch 2004). In this paper we report work on the remote French Polynesian island of Rapa, located in East Polynesia equidistant between New Zealand and Easter Island, and 513km from its nearest neighbour (Raivavae) on the southeastern extremity of the Austral Group (Guillin 2001). The island is small (35[km.sup2]) and horseshoe-shaped; a breeched caldera that forms a natural amphitheatre surrounding Ha'urei Bay (Chubb 1927; Figure 1). At historic contact (AD 1791), an estimated 1500 people were living on the island in a series of heavily fortified hilltop communities distributed along the ridgeline surrounding Ha'urei Bay (Vancouver 1801 I: 214-5). Here we report on the earliest colonisation phase of the island and establish a chronology for demographic expansion, fortification, and human induced environmental change.

Age of colonisation

Opinions about the age of initial human entry to East Polynesia have varied considerably, but the recent trend has been toward younger estimates. Spriggs and Anderson (1993) suggested initial colonisation in the interval AD 300-600, but additional research on sites of the colonisation era (Anderson et al. 1999; Anderson & White 2001; Anderson & Sinoto 2002; Anderson et al. 2003; Rolett & Conte 1995; Rolett 1998; Steadman et al. 1994; Tuggle & Spriggs 2000; Weisler 1996) indicates a stronger probability of arrival later in the first millennium AD. This period is also consistent with recent evaluations of the initial age of anthropogenic affects upon vegetation change (Anderson 1995, 2002; Athens et al. 1999; Burney 2002; McGlone & Wilmshurst 1999). Weisler (1996) puts the beginning of occupation in the Pitcairn Island group at about AD 800, although the earliest date is not securely tied to cultural events, and the age of colonisation on Easter Island, best recorded by radiocarbon dates from Anakena associated with bones of extinct birds, is approximately AD 1000 (Steadman et al. 1994). In the south-eastern region of East Polynesia, settlement of the Gambier Islands began about AD 1100 (Anderson et al. 2003). It is worth noting, however, that Rapa is the southernmost island in East Polynesia and that all of South Polynesia, which lies to the south-west of it, was colonised later again, about AD 1200 (Anderson 1991,2000).

Our excavations on Rapa were divided between fortifications and coastal rockshelters, the latter being expected to yield the better evidence of initial habitation on the island because they were readily accessible for habitation to the earliest colonists. Rockshelters are scarce on the island and most of them are less than 10m in maximum dimension (see Figure 1). However, the Tangarutu rockshelter in Anarua Bay (Figure 2A), on the more sheltered western coast, is so conspicuous from the sea, and so capacious (80 x 40m) that it is likely to have been used from the earliest period of settlement. …