Abstract
The timing of human colonization of East Polynesia, a vast area lying between Hawai'i, Rapa Nui, and New Zealand, is much debated and the underlying causes of this great migration have been enigmatic. Our study generates evidence for human dispersal into eastern Polynesia from islands to the west from around AD 900 and contemporaneous paleoclimate data from the likely source region. Lake cores from Atiu, Southern Cook Islands (SCIs) register evidence of pig and/or human occupation on a virgin landscape at this time, followed by changes in lake carbon around AD 1000 and significant anthropogenic disturbance from c. AD 1100. The broader paleoclimate context of these early voyages of exploration are derived from the Atiu lake core and complemented by additional lake cores from Samoa (directly west) and Vanuatu (southwest) and published hydroclimate proxies from the Society Islands (northeast) and Kiribati (north). Algal lipid and leaf wax biomarkers allow for comparisons of changing hydroclimate conditions across the region before, during, and after human arrival in the SCIs. The evidence indicates a prolonged drought in the likely western source region for these colonists, lasting c. 200 to 400 y, contemporaneous with the phasing of human dispersal into the Pacific. We propose that drying climate, coupled with documented social pressures and societal developments, instigated initial eastward exploration, resulting in SCI landfall(s) and return voyaging, with colonization a century or two later. This incremental settlement process likely involved the accumulation of critical maritime knowledge over several generations.
Highlights
We propose that drying climate, coupled with documented social pressures and societal developments, instigated initial eastward exploration, resulting in Southern Cook Islands (SCIs) landfall(s) and return voyaging, with colonization a century or two later
Those using short-lived materials (SLMs; ≤10 y) with little in-built age [1, 2], along with U-Th dating [3], have gone some way toward resolving the chronology of human settlement in East Polynesia, a region distinguished by a high degree of cultural, biological, and linguistic similarity [4]
High-precision chronologies are available for several central archipelagos, including the Cook [3, 5], Society [6], and Marquesas islands [7], along with Mangareva [8], unambiguously placing Polynesians in the central East Polynesian core by the 12th century AD
Summary
Lake Emoatul (17°43′57.48′′S, 168°24′53.58′′E), Efate Island, Vanuatu is a closed, 0.3-km freshwater body at an altitude of 119 metres above sea level (m.a.s.l.) within a relatively small catchment (0.98 km2) surrounded by moist montane forest with limited subsistence gardening and arboriculture. The age measurements obtained for SLMs drive the Bayesian modeling and constrain the depth interval for initial fecal markers to AD 800 to 1004 (2σ) These unequivocal indicators of mammalian feces (pig and/or human) predate changes in lake productivity and major catchment disturbance, suggesting early humans and/or pigs associated with human arrival visited this significant water source but had negligible impacts on the immediate lake environment. Seven other proxies recovered from distinct lamina between 215 and 188.5 cm inform on subsequent changes in lake productivity and the onset of consequential catchment disturbances (Fig. 2 and Table 1) These include C/N ratios and δ13C of organic carbon, which indicate the organic matter is from a terrestrial carbon source, and total organic carbon, which is a measure of lake productivity [22, 23]. Local hydroclimate on Atiu became increasingly wet toward the end of phase 3 (colonization) and leading into phase 4 (establishment)
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