Definition radiocarbon dating

New Zealand's well-established short colonization chronology (11), which was further shortened and refined by dates from nonarchaeological sites on short-lived woody seed cases gnawed by the Polynesian-introduced and compared with terrestrial avian eggshell from an early human cemetery (4, 15), and the short colonization chronology for Rapa Nui (6), are both confirmed here (EAEM–LAEM range: A. More striking are the results from the Marquesas and Hawaiian archipelagos which now indicate a much shorter chronology (EAEM–LAEM range: A. The consistent age ranges on short-lived samples for colonization on islands in the far reaches of East Polynesia imply reliable measurement of the same dispersal and colonization event over this vast region.

definition radiocarbon dating-35definition radiocarbon dating-18definition radiocarbon dating-67

For each graph, individual ranges (68% probability) of Class 1 calibrated radiocarbon dates are shown as black horizontal lines; circles represent median (bottom axis). other eastern Polynesian islands.) Estimates for the timing of colonization for East Polynesian archipelagos or islands. (The proportion of radiocarbon-dated sample materials in each overall reliability class is shown in Fig. Class 1 dates are dominated by short-lived plant materials (such as small twigs, leaves, and seeds) in contrast to Class 2 and 3 dates, which are dominated by long-lived plant remains and unidentified charcoal, sample types that are often unreliable, as they can introduce substantial error through in-built age.

Red dashed line indicates sum of probability distributions (left axis). 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. For each graph, individual ranges (68% probability) of Class 1 calibrated radiocarbon dates are shown as black horizontal lines; circles represent median (bottom axis). The high proportion of unidentified charcoal in Class 3 shows this category of dated materials in the dataset also tends to have large measurement errors. Age estimates for initial colonization of the Gambier archipelago are unusually broad (167-y difference between the EAEM and LAEM, i.e., between A. ∼11) compared with all other islands (average difference of 55 y between earliest and latest estimates). ∼1219–1266, respectively), some 200–500 y later than widely accepted (16, 17), placing them in close agreement with both New Zealand and Rapa Nui.

More radiocarbon dating of short-lived materials from islands lacking enough Class 1 dates for robust chronologies (Gambier, Tuamotus, Australs, Northern Cooks, Kermadec, Norfolk, and Chathams; Fig. In addition, closer scrutiny of dates at the older end of the Class 1 age ranges may also increase the precision of estimates for initial colonization.

For example, some of the oldest dates for the Auckland Islands are based on small-diameter (2-cm) wood from long-lived trees (), which, despite the size of twigs, may still contain inbuilt age and create an artificial tail to the probability distributions (19).

Here accuracy is defined based on those samples that can provide a date that is the “true” age of the sample within the statistical limits of the date.

Precision is controlled by small laboratory measurement and calibration errors.

This might be explained, in cultural terms, by rapid population growth on relatively small islands, purposeful exploration, and technical innovation in sailing vessels, such as the advent of the double canoe that effectively erased distance as a barrier to long-range voyaging (c.f.

European voyaging in the Atlantic and Indian Ocean in the 15th century).

These conflicting chronologies preclude establishment of a regional pattern of settlement and hinder our understanding of cultural change and ecological impacts on these island ecosystems. 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. ∼10 (orange shading), and second to the remote islands between A. It used a “chronometric hygiene” protocol to exclude dates with high uncertainty and to provide a chronology that proposed initial settlement A. Conflicting estimates for initial colonization in East Polynesia create great uncertainty about the historical framework within which human mobility and colonization, variations in human biology and demography, and the rates and types of human-induced ecological impacts to island ecosystems must be explained.

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