High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia

Abstract

The 15 archipelagos of East Polynesia, including New Zealand, Hawaii, and Rapa Nui, were the last habitable places on earth colonized by prehistoric humans. The timing and pattern of this colonization event has been poorly resolved, with chronologies varying by >1000 y, precluding understanding of cultural change and ecological impacts on these pristine ecosystems. In a meta-analysis of 1,434 radiocarbon dates from the region, reliable short-lived samples reveal that the colonization of East Polynesia occurred in two distinct phases: earliest in the Society Islands A.D. ∼1025-1120, four centuries later than previously assumed; then after 70-265 y, dispersal continued in one major pulse to all remaining islands A.D. ∼1190-1290. We show that previously supported longer chronologies have relied upon radiocarbon-dated materials with large sources of error, making them unsuitable for precise dating of recent events. Our empirically based and dramatically shortened chronology for the colonization of East Polynesia resolves longstanding paradoxes and offers a robust explanation for the remarkable uniformity of East Polynesian culture, human biology, and language. Models of human colonization, ecological change and historical linguistics for the region now require substantial revision.

Fig. 1.

Islands of East Polynesia, summarizing the two phases of migration out of West Polynesia (blue shading): first to the Society Islands (and possibly as far as Gambier) between A.D. ∼1025 and 1121 (orange shading), and second to the remote islands between A.D. ∼1200 and 1290 (yellow shading).

Fig. 2.

Proportion of radiocarbon-dated sample materials making up each overall reliability class (data from Table S1). Diameter proportional to square root of n.

Fig. 3.

Chronometric range (68% probability) of calibrated radiocarbon dates for East Polynesian islands, for reliability Classes 1–3 as defined in Materials and Methods. Boxes show minimum and maximum calibrated ages for dates within each class. The reliable Class 1 dates consistently reveal a short chronology for each island or archipelago where data are available. In contrast, Class 2–3 dates, which are based on materials that have a high risk of imprecision and/or inaccuracy, have a larger spread of ages, and these are often used to support longer chronologies in the region.

Fig. 4.

(A) Estimates for the timing of colonization for East Polynesian archipelagos or islands. For each graph, individual ranges (68% probability) of Class 1 calibrated radiocarbon dates are shown as black horizontal lines; circles represent median (bottom axis). Red dashed line indicates sum of probability distributions (left axis). Solid blue line = cumulative probability (right axis) which provides a means of assessing our confidence that colonization occurred no later than a particular date. For the Society Island dates, this was set to A.D. 1200 based on the assumption that we have 100% confidence that colonization had occurred by this time; and for the remaining islands with Class 1 dates, this was set to A.D. 1300. Blue dashed line represents LAEM in years A.D. Our LAEM and our EAEM for initial colonization are listed below each island group and are represented by the yellow band. (B) Distinct separation between colonization ages for the Society Islands (and possibly Gambier) vs. other eastern Polynesian islands.