That is, to accept only those dates that () are capable of providing a calibration that is close to the “true” age of the actual target event (i.e., human activity).
The reliable Class 1 dates consistently reveal a short chronology for each island or archipelago where data are available. Our LAEM and our EAEM for initial colonization are listed below each island group and are represented by the yellow band.
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.(A) Estimates for the timing of colonization for East Polynesian archipelagos or islands. (B) Distinct separation between colonization ages for the Society Islands (and possibly Gambier) vs. Our LAEM and our EAEM for initial colonization are listed below each island group and are represented by the yellow band.
Our main objective is to establish the most accurate age, or ages, for initial colonization in East Polynesia.
To accomplish this, it is necessary to be conservative in evaluating the usefulness of data.
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.
This is an important result that has implications for colonizing process (discussed below).We first categorized all radiocarbon-dated materials into one of six sample material types: short-lived plant, long-lived plant, unidentified charcoal, terrestrial bird eggshell, bone, and marine shell (Fig. Dates on these materials were then sorted into reliability classes, according to whether there was potential for any disparity between the age of the radiocarbon event (i.e., Fig. Calibration probabilities were then calculated for the subset of reliable dates to derive the most precise (within radiocarbon calibration error) estimate for the age of initial colonization on all East Polynesian island groups (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.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.The narrow age distribution of colonization through remote East Polynesia is not explained as merely a function of analyzing smaller subsets formed by Class 1 dates.