From a biological standpoint, these two theories implied quite different genetic inheritances. In the express train model, the Austronesian people who ultimately became Polynesians sped through the intermediate region of Melanesia so fast that there was no genetic mixing. The entangled bank model, on the other hand, considered these two populations—the migrating Austronesians and the local Melanesians—so thoroughly intertwined that they were hard to tell apart, and envisioned the Polynesians as having emerged out of this tangle of cultures and peoples. At its heart, this was essentially the same problem that had vexed somatologists like Louis R. Sullivan and Te Rangi Hiroa in the 1920s and ’30s: How much of a connection was there between Polynesians and Melanesians? Were they entirely distinct groups? Or were they more like cousins? And how significant was the Asian/Austronesian component? The hope was, of course, that with the sequencing of the human genome, the matter would be settled once and for all.
THE FIRST RESEARCH into Polynesian genetics involved variations in mitochondrial DNA, a unique kind of DNA inherited exclusively from the maternal line. By the early 1990s it had become clear that virtually all Polynesians carry a distinctive combination of mitochondrial DNA mutations known as the “Polynesian motif,” which can be traced back to the islands of Indonesia and the Philippines. This discovery lent credence to the express train model, but just a few years later it was contradicted by researchers using a different genetic method.
If mitochondrial DNA is inherited exclusively from the mother, Y chromosomes, which are found only in males, are indicative of descent through the paternal line. Unlike Polynesian mitochondrial DNA, Polynesian Y chromosomes did not suggest an “out of Asia” story but instead pointed to an ancestral source inside Melanesia. (An earlier study from the 1980s had also found evidence for Melanesian input into Polynesian genes in the form of a mutation associated with malaria resistance. This mutation, which crops up with surprisingly high frequency among Polynesians, was unexpected, because Polynesia is not a malarial region. Melanesia, however, is.)
These conflicting results prompted researchers to propose yet a third migration model, sometimes known as the “slow boat.” According to this model, the ancestors of the Polynesians had originated in Asia, but instead of shooting through on their way to Remote Oceania, they had dawdled, “leaving behind their genes and incorporating many Melanesian genes,” before moving on to the wider Pacific. Incidentally, it is not immediately obvious why there should be this discrepancy between the maternal and paternal inheritances of Polynesians. But one possibility is that migrating Austronesian populations may have tolerated the incorporation of outsider males while keeping females within the community, a pattern that was also seen during the colonial period.
These early genetic studies were based on the DNA of living Polynesians, but it is important to recognize that the genes of modern populations may not tell us everything we want to know about people in the past. Over the course of many hundreds of years, Polynesians have undergone a number of genetic bottlenecks, periods when the population was suddenly and dramatically reduced. This would have happened any time a small group of people set off from one island to colonize another; it might have happened as a result of natural disasters; it definitely happened in the colonial era in places like the Marquesas, where the population crashed. As a result, the full genetic diversity of the original colonists may no longer be represented in the DNA of people now living, some strands of their genetic history having been lost along the way.
One solution to this problem is to look directly at the genes of ancient Polynesians. But this has been difficult to do in the Pacific for a variety of reasons, not least of which is that the warm, wet tropics are a bad environment for the preservation of ancient DNA. Sites containing suitable genetic material are few and far between, which is why the discovery, in 2003, of the oldest cemetery in the Pacific was such a big deal. The site, known as Teouma, was accidentally discovered by a bulldozer driver who was quarrying soil for a prawn farm in an abandoned coconut plantation on the island of Éfaté, in Vanuatu. What he saw, sticking out of the ground, was not a bone but a large piece of decorated pottery, which he passed along to a friend who had worked for the Vanuatu Cultural Centre and who immediately recognized it for what it was. Thus, Teouma revealed itself as not only one of the great repositories of Lapita ceramics—flat-bottomed dishes, cylinder stands, and large, elegantly shaped vessels—but a burial ground containing nearly seventy inhumations.
Of course, what everyone wanted to know was what the DNA of these ancient skeletons could tell us, and the results, when they finally appeared, were somewhat surprising. The first ancient DNA results from Teouma showed that all three of the individuals tested—all women—carried the “Polynesian motif” and were genetically similar to indigenous populations from the Philippines and Taiwan. But they also showed that these early Lapita people had essentially no Melanesian ancestry. What this seemed to suggest was that the Polynesians had acquired their Melanesian inheritance at some later point. But where and when and how remains unknown.
STUDYING HUMAN DNA can be difficult, for reasons that are not purely technical. The history of biological research on indigenous communities is not a particularly happy one, and many of these communities have expressed skepticism about DNA research, feeling that they have been treated as “specimens” for quite long enough, and doubting whether any of the benefits of such work would ever flow back to them. Also, in many parts of Polynesia, there is a high degree of cultural sensitivity surrounding anything having to do with ancestors and the dead. One place where this has all come together fairly dramatically is the so-called moa-hunter site at Wairau Bar.
Much of the archaeological material uncovered by Jim Eyles and Roger Duff at Wairau Bar in the 1940s and ’50s, including moa eggs, adzes, ornaments, and kōiwi tangata, or human remains, was handed over to the Canterbury Museum for “security and long-term preservation” by the site’s owners and lease holders at the time. Duff claimed to have had the cooperation of the local Māori tribe, Rangitāne o Wairau, but over time Rangitāne came to resent the disturbance of their tūpuna, or ancestors, and the removal of taonga, or treasures. And in the late 1960s they embargoed the site, denying all further requests for excavations.
This meant that all through the 1970s, ’80s, and ’90s—a period of significant scientific advances in both genetics and radiocarbon dating—the evidence of Wairau Bar was essentially off-limits. Then, in 2008, the Rangitāne tribal authority made a deal with the University of Otago and the Canterbury Museum. In keeping with a worldwide trend toward the repatriation of artifacts, art objects, and especially human remains, the museum would return the kōiwi tangata (though not the ornaments or the tools). In exchange, Rangitāne would permit a full biological assessment of the skeletal material and the removal of small samples of bone and teeth for DNA analysis before the remains were formally reinterred. Rangitāne would recover their tūpuna and lay them to rest, and the anthropologists would get a new opportunity to see what could be discovered.
One finding that pleased local members of the Rangitāne tribe was the discovery that several of them shared a direct genetic link with some of the kōiwi tangata, including a seven-hundred-year-old woman known as “Aunty.” But another interesting revelation was that the people buried at Wairau Bar—still the oldest site ever discovered in New Zealand—were much more genetically diverse than anyone had imagined. This, in turn, suggested that New Zealand’s founding population was larger than expected—not just a few canoeloads of closely related families but perhaps hundreds of unrelated immigrants—and that the source populations in Tahiti and the Cook Islands were also large and genetically diverse. After a century of steadily shrinking expectations—the presumption of fewer and fewer voyages, smaller and smaller founding populations, more and more isolation, less and less interaction—this pushed the story back in the direction of the “heroic” narratives of the nineteenth century, with their frequent return voyage
s and their colonizing fleets.
THERE IS A clever alternative to working with human DNA, however, that obviates many of these problems. Pioneered by a University of Otago anthropologist named Elizabeth Matisoo-Smith, it involves looking at the genes of what are known as “commensal” animals, that is, animals that travel in company with humans and whose history of movement can be used as a proxy for the movement of their human hosts. Polynesians brought an assortment of such creatures with them when they sailed into the Pacific, including pigs, dogs, chickens, and rats. Of these, the ideal animal for study turns out to be Rattus exulans, the “wandering” Pacific rat.
Rattus exulans cannot get to islands except in the company of humans. It does not interbreed with the rats introduced to the Pacific by Europeans—Rattus rattus, the black rat, and Rattus norvegicus, the Norwegian. And since it dislikes wet places, it is thought unlikely to have traveled in the holds of European ships. Taken together, what this means is that the Pacific rats living on the islands today are very likely the direct descendants of rats that were brought by the first Polynesian voyagers. Best of all, there are plenty of rat bones in Polynesian archaeological sites, and no one minds if you dig them up or destroy them to extract their DNA.
Studies of rat DNA confirm that the Societies, the Australs, and the Cooks were a “general homeland region” for the islanders of the central and eastern Pacific—the Hawaiki from which the Māori, Marquesans, Rapa Nui, and Hawaiians set out on the final legs of their great journeys. They also show that rats in New Zealand were—like the kōiwi tangata from Wairau Bar—surprisingly genetically diverse, meaning that they were likely to have been introduced multiple times, by lots of different canoes carrying lots of different rat populations. On Easter Island, however, the rat story is quite different. Easter Island rats show so little genetic variation that they might have been introduced to the island just once—perhaps even by a single canoeload of people who then became effectively marooned.
So far, genetics has in some cases confirmed what we thought we already knew; in others it has begun to alter narratives that had seemed settled. But we are just at the very dawn of these discoveries, and the one thing that seems irrefutable at this point is the enormous potential of this research. As one DNA researcher recently put it, “It’s like turning on an electric light in a dark cave where before there were only small wavering candles.”
THE OTHER AREA that has attracted quite a bit of attention in recent years is the question of when the islands of Remote Oceania were first settled. When radiocarbon dating was first developed, in the late 1940s and ’50s, it was a spectacular breakthrough: the first objective, verifiable means of establishing chronologies for periods of human history for which there was no written record. But, as with any technology, there was room for improvement, and significant technological advances have been made in the decades since. It is now possible to date something as small as an individual seed, which means that the process is much less destructive. The new methods are also increasingly precise, with error ranges a mere fraction of what they once were, and there is a much better understanding of the potential sources of error. All these improvements—but particularly the last—have led to a major shift in thinking about when the islands of Polynesia were first settled.
Back in the 1950s, when the first radiocarbon results were coming in from Polynesia, a number of very early dates were obtained for archipelagoes in the central and eastern Pacific. These included Suggs’s tantalizing date of 150 B.C. from charcoal in a Marquesan hearth and Emory’s A.D. 124 from a dune on the Big Island of Hawai‘i. Early dates are inherently exciting—lighting up the dimmest recesses of the past—and these findings were doubly significant, representing, as they did, the first scientific answers to the question of when human beings had first colonized the remote Pacific. Together with a cluster of later dates, they formed the basis of an orthodox chronology that went something like this: the arrival of the Lapita people in the Tonga/Samoa region, around 1000 B.C., followed by a roughly one-thousand-year pause, and the gradual expansion into the Polynesian Triangle in the first few centuries A.D. It was a narrative that seemed to make sense, allowing plenty of time for Polynesian culture to “set” in the Samoa/Tonga region—that is, for the Lapita people to become Polynesians—as well as sufficient time for the Polynesians to explore the widest, emptiest, and most navigationally challenging reaches of the Pacific Ocean.
But then, in the early 1990s, a group of revisionist archaeologists began to question this timeline. By this point, a large number of radiocarbon dates from Polynesia had accumulated, but they had been produced under widely varying conditions—at different times and in different places, by different researchers using different standards and employing different laboratories, which also used different protocols. The moment had come, these archaeologists argued, to reassess this corpus of dates, “to weed out” those that could not be relied upon, and “to build a secure chronology with those that remain.” They referred to this plan, with dry archaeological humor, as a program of “chronometric hygiene.”
They began by suggesting that all the radiocarbon dates from the 1950s and ’60s should be treated with “considerable caution.” They rejected any date for fish, human, or animal bone, sea urchin spines, land snails, freshwater shells, and anything else that could be “grossly affected by the uptake of old carbon.” They rejected dates based on charcoal from long-lived species of trees, as well as all the early run dates from the Gakushuin University radiocarbon laboratory in Japan (on the grounds that they were weirdly inconsistent, both too early and too late). They rejected samples made up of more than one substance, like charcoal and burnt earth, or sugarcane, ti tree, and reeds; as well as samples without any clear cultural context, such as random chunks of charcoal not associated with any human activity. They also tossed out dates that did not overlap at two standard deviations with other dates from the same context; stratigraphically inverted dates; and dates that were anomalous in some other way.
It was a lot to get rid of, and many of the dates on which the orthodox chronology had been built were summarily swept away. Of the one hundred nine Hawaiian dates, only twenty-one were thought good enough to keep; from the Marquesas and Easter Island, just ten from a total of twenty-three survived. Out went Suggs’s groundbreaking early dates from the Marquesas; out went Duff’s dates from Wairau Bar; out went Emory’s early dates from Hawai‘i; out went Heyerdahl’s Easter Island dates. When they surveyed what was left, the story looked quite different. The Lapita people were still envisioned as having reached Samoa and Tonga in the neighborhood of 900 B.C., but the initial settlement of central and eastern Polynesia had moved much closer to the present. According to the new orthodoxy, none of the archipelagoes of central and eastern Polynesia (the Society Islands, Hawai‘i, the Marquesas, Easter Island, the Cooks) is thought to have been settled before the end of the first millennium A.D., while the discovery and settlement of New Zealand was pushed as far forward as A.D. 1200.
The implication of these much later dates is curious. Coming hard on the heels of the lightning-fast Lapita expansion, the long pause in Tonga/Samoa now seems even more mysterious. Having reached so far out into the Pacific, what kept them sitting there for nearly two thousand years? While it is certainly true that the ocean gets emptier east of Samoa, the voyages they had already made were far from trivial. Clearly, they had the technology; what they do not seem to have had is the desire or the need. And then, as though they had been suddenly pricked into action, what made them set out and conquer the ten million square miles of the Polynesian Triangle? And how did they do that in just a few hundred years?
There have been some intriguing attempts to explain this new timeline in terms of climatic variation—changes in weather that might have enabled or impeded voyaging during different spans of time. One computer simulation investigates the role that the El Niño/Southern Oscillation might have played in Polynesian voyaging: warmer El Niño conditions reduce precipita
tion in the western Pacific, making it easier to travel eastward (say, from Samoa to Tahiti), while cooler La Niña years favor movement from the central Pacific southwest toward New Zealand. A second study suggests that there may have been “climate windows,” lasting a century or more, during which the weather in the Pacific shifted in such a way as to facilitate sailing over certain notoriously difficult routes.
Another implication of this shorter chronology is that much less time must have elapsed between the Polynesian discovery of some of these islands and the arrival of the first European eyewitnesses—in the case of New Zealand, perhaps as little as four hundred years. But is this long enough to fully populate the islands, alter their landscapes (in some cases dramatically), extirpate a wide variety of creatures, adapt horticultural practices to local conditions (drought-prone Easter Island, chilly New Zealand), develop a distinct range of customs and languages, give up long-distance voyaging, lose geographic knowledge, and become the homebodies they appeared to be when the Europeans first arrived? One does not feel, reading the accounts of the early European explorers, as though the people they discovered in the islands of Polynesia had only just gotten there. But the math can be made to work: a founding population of 250 people (say, five canoes) with a growth rate of 1.5 percent per year would reach a population of nearly 100,000 in four hundred years.
But perhaps the single most interesting thing about the new orthodoxy is the way it appears to corroborate the chronologies extracted from Polynesian oral traditions. Both Abraham Fornander and S. Percy Smith developed timelines for the settlement of Oceania based on Polynesian genealogies recorded in the nineteenth century. Both describe a two-step settlement scenario, with a vague and poorly substantiated early discovery phase followed by a well-defined period of colonization around the end of the first millennium A.D. Fornander specifically noted an efflorescence of tales about “bold expeditions, stirring adventures, and voyages undertaken to far-off lands,” from which he deduced an era of “national unrest” and “tribal commotion” right around the year 1000. Smith similarly proposed a muddled early settlement phase for New Zealand, but his dates for the arrival of the first named Māori ancestors were 1150 and 1350, exactly straddling the date proposed for the settlement of New Zealand in the cleaned-up radiocarbon chronology. Thus, you might say, the new science, having displaced the old science, agrees surprisingly well with the pre-science.
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