Jul 12

Sidestep: How quickly was East Polynesia colonised?

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 years, 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.

Previously supported longer chronologies have relied upon radiocarbon-dated materials with large sources of error, making them unsuitable for precise dating of recent events. Dramatically shortened chronology for the colonization of East Polynesia resolves long standing 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.

During the last prehistoric expansion of modern humans, Polynesians from the Samoa-Tonga area dispersed through more than 500 remote, subtropical to subantarctic islands of East Polynesia (a cultural region encompassing the islands of New Zealand, Chathams, Auckland, Norfolk, Kermadecs, Societies, Cooks, Australs, Gambier, Tuamotu, Marquesas, Line, Rapa Nui, and Hawaii), an oceanic region the size of North America (Fig. 1). The timing and sequence of this expansion, debated vigorously since Europeans rediscovered the islands of East Polynesia (1, 2) and most intensively with the advent of radiocarbon dating (3, 4), remains unresolved. On many islands, irreconcilable long and short settlement chronologies coexist that vary by more than 400–1,000 y (4). 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.

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).

The last systematic analysis of radiocarbon dates from archaeological and paleoecological sites throughout East Polynesia, published 17 y ago, was based on 147 radiocarbon dates (5). It used a “chronometric hygiene” protocol to exclude dates with high uncertainty and to provide a chronology that proposed initial settlement A.D. 300–600 in the Marquesas, A.D. 600–950 in the central, northern, and eastern archipelagos, and no earlier than A.D. 1000 in New Zealand. This analysis shortened East Polynesian prehistory just at the time when accelerator mass spectrometry (AMS) radiocarbon dating became available for very small samples (e.g., individual seeds). Subsequent studies using precise AMS dating of short-lived materials alone have generally supported short chronologies. However, these chronologies continue to be dismissed by some scholars on hypothetical grounds of missing evidence or archaeological invisibility, and in favor of radiocarbon dates on materials (typically unidentified charcoal with high inbuilt age potential) incapable of providing a precise age for the event being dated. 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.

The distribution of calibrated age ranges for all classes of radiocarbon dates shows a clear pattern across the entire region without exception, the range for all Class 1 calibrated dates (68% probability; n = 207) is considerably narrower than it is for Class 2 and 3 dates, regardless of their individual stratigraphy or context. Class 1 calibrations range only from A.D. 1025 to 1520, in contrast to those of Class 2–3 dates, which extend back to 500 B.C. This pattern reflects the higher precision and accuracy of the reliable targets that make up Class 1 dates (i.e., short-lived materials with SEs <10%), whereas the extended ranges of Class 2 and 3 dates correspond with greater imprecision from inbuilt age and marine calibration problems associated with the unidentified charcoal and marine shell dates that dominate these classes (Fig. 2). Radiocarbon dates in Classes 2 and 3, despite providing imprecise calibrations, have formed the basis of arguments for settlement across East Polynesia in the first millennium A.D. or earlier.

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 Rattus exulans 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.D. ∼1230–1282 and A.D. ∼1200–1253, respectively) but with much larger sets of Class 1 dates. This clearly demonstrates that even a relatively small subset of precise radiocarbon dates on highly reliable samples is capable of providing a secure chronology, both from relatively small islands such as Rapa Nui, and from New Zealand, the largest and most topographically complex island group in Polynesia. More striking are the results from the Marquesas and Hawaiian archipelagos which now indicate a much shorter chronology (EAEM–LAEM range: A.D. 1200–1277. and A.D. ∼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 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). 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. 3) is desirable to further test the pattern. 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 (Dracophyllum spp. and Metrosideros umbellata), which, despite the size of twigs, may still contain inbuilt age and create an artificial tail to the probability distributions (19).

The consistent, contemporaneous nature of East Polynesian age distributions is better explained by extraordinarily rapid migration from the centrally positioned East Polynesian islands in the 13th Century.

Migration into eastern Polynesia began after a 1,800-y pause since the first settlement of Samoa, ∼800 B.C. (12), which implies a relatively sudden onset of whichever environmental or cultural factors were involved. Our results show that, quite soon after reaching the central islands, Polynesian seafarers discovered nearly every other island of the eastern Pacific within about one century, a rate of dispersal unprecedented in oceanic prehistory. 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). However, environmental factors or disaster could also have been influential. Our data have narrowed the coincidence of dispersal throughout East Polynesia (A.D. ∼1200–1300) to a period of peak El Niño occurrence during the last millennium, when increased frequencies of tropical westerly and subtropical easterly winds favored access to the more remote islands.

The substantially shorter chronologies may now resolve existing paradoxes or challenge alternative views about the prehistory of East Polynesia. For example, the earliest presence of sweet potato (Ipomoea batatas) in Mangaia, Cook Islands, dated to A.D. 1210–1400 and was regarded as a late occurrence (21), and similarly late dates on sweet potato from Hawaii (22) could now actually represent an initial introduction of sweet potato to these islands with colonization, and to East Polynesia more generally, regardless of whether Polynesians reached South America or Amerindians reached Polynesia (23). Conversely, linguistic similarity, often used to trace phylogenetic relationships of populations in East Polynesia according to a longstanding model of relatively slow, incremental expansion (24), now needs to be reconsidered in terms of specific founder effects and isolation, especially in the case of Rapa Nui. Similarly, the rise of monumental, ceremonial architecture within a much shorter regional chronology (25) implies a different kind of historical development as well as likely continuity with comparable structures in western Polynesia (12, 26). Finally, the remarkable artifact similarities documented in the “archaic East Polynesian” assemblages of the Societies, Marquesas, New Zealand, and other islands reflect homology of forms (e.g., in fishhooks, adzes, and ornaments) with late and rapid dispersals over the region (27, 28). Indeed, similarities of form attributed to continuing interarchipelagic contacts may actually reflect sharing that occurred in mobility associated with colonization and not a later phase of long-distance interactions.

Later colonization also condenses the timeframes of human impacts on island ecosystems, particularly deforestation, and plant and animal extinctions. The remarkable speed of environmental transformations is now measured perhaps in decades rather than centuries and includes impacts on both terrestrial and marine biota caused by human hunting; predation by introduced animals such as the Polynesian rat (Rattus exulans), dog (Canis familiaris), and pig (Sus scrofa); as well as the human use of fire within the short occupational chronology that we propose. All of these demand major revision of previously held assumptions regarding the rate, causes, and consequences of extinctions with human impacts on pristine island ecosystems. For example, populations of at-risk species that are sensitive to predators introduced at the time of initial Polynesian colonization may be declining at much faster rates than previously believed (4, 30, 31). Abbreviating the duration of human settlement impacts by more than 50% on some islands makes a great difference to interpreting the decline of indigenous biota. Whereas these declines were thought to have occurred over a thousand years or more, it now appears that, in most cases, several hundred years was all it took. Furthermore, previously supported implications that there was a long period of relatively benign interaction among humans, rats, dogs, pigs, and indigenous vertebrates now need revision, as our refined model of colonization chronology suggests that impacts had to have been immediate, severe, and continuous.

The results show that, after a relatively brief period of establishment in central East Polynesia, there was a remarkably rapid and extensive dispersal in the thirteenth century A.D. to the remaining uninhabited islands. This rate of human expansion is unprecedented in oceanic prehistory. Our model, although falsifiable, is likely to prove robust with further high precision radiocarbon dating of short-lived materials from those East Polynesian islands that currently lack secure chronologies based on such materials.

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The above was gleaned from the following in 2010 - https://www.pnas.org/content/108/5/1815

This information as with other articles produced by those who wrote the above, advise that Polynesians did not come from Taiwan or Asia. Seems weird seeing as that is the path of migration. But the articles were written and accepted as correct..... until proved wrong.

UNTIL PROVED WRONG...

Not all of what we as human beings currently accept as correct, is correct. Yet we do accept it as correct until it is proved wrong, and then wonder why we didn't see it before given the evidence or suggestive evidence. Once again...