Hundreds of iconic moai statues stand testament to the vibrant civilization that once inhabited Easter Island, but there are far fewer clues about why this civilization mysteriously vanished. Did they shortsightedly exhaust the island's resources? Were they decimated by European illnesses and slave trade? Or did stow-away rats devastate the native ecosystem? Such theories have spread widely, but recent evidence shows that the truth is not as simple as any one of these alone.
"These different interpretations may be complementary, rather than incompatible," said Dr. Valentí Rull. "In the last decade, there's been a burst in new studies, including additional research sites and novel techniques, which demand that we reconsider the climatic, ecological and cultural developments that occurred." Rull is a senior researcher of the Spanish National Research Council in Barcelona, Spain, and the lead author of an overview on the holistic reassessment of Easter Island history.
Until recently, the evidence has been limited. Prior sedimentary samples--commonly used as historical records of environmental change--were incomplete, with gaps and inconsistencies in the timeline. Furthermore, past interpretations relied heavily on pollen alone, without incorporating more faithful indicators of climate change. Due to this uncertainty, many fundamental questions remain, not only about why the culture disappeared, but also precisely when these events occurred and how this civilization developed in the first place.
Using the latest analytical methods, Rull and his collaborators are beginning to shed light on many of these questions. Complete sedimentary samples now show a continuous record of the last 3000 years, showing how droughts and wet seasons may have influenced the island's population. Sea travel depended on such weather patterns, resulting in periods of cultural exchange or isolation. Rainfall also impacted native palm forests, with droughts potentially contributing to the island's eventual deforestation. Radiocarbon dating and DNA analysis of artifacts and human remains are also showing where the inhabitants lived on the island, what they farmed and ate, and the influence of cultures beyond their Polynesian ancestors.
"These findings challenge classical collapse theories and the new picture shows a long and gradual process due to both ecological and cultural changes. In particular, the evidence suggests that there was not an island-wide abrupt ecological and cultural collapse before the European arrival in 1722," said Rull.
A University of Otago, New Zealand, PhD student analysing dental calculus (hardened plaque) from ancient teeth is helping resolve the question of what plant foods Easter Islanders relied on before European contact.
Known to its Polynesian inhabitants as Rapa Nui, Easter Island is thought to have been colonized around the 13th Century and is famed for its mysterious large stone statues or moai.
Otago Anatomy PhD student Monica Tromp and Idaho State University's Dr John Dudgeon have just published new research clearing up their previous puzzling finding that suggested palm may have been a staple plant food for Rapa Nui's population over several centuries.
However, no other line of archaeological or ethnohistoric evidence supports palm having a dietary role on Easter Island; in fact evidence points to the palm becoming extinct soon after colonization.
Nevertheless, the researchers had found that the vast majority of phytoliths (plant microfossils) embedded within the calculus were from palm trees.
The teeth were from burials excavated in the early 1980s from multiple coastal archaeological sites around the island.
They lived on a remote dot of land in the middle of the Pacific, 2,300 miles (3,700 km) west of South America and 1,100 miles (1,770 km) from the closest island, erecting huge stone figures that still stare enigmatically from the hillsides.
But the ancient Polynesian people who populated Easter Island, or Rapa Nui, were not as isolated as long believed. Scientists who conducted a genetic study, published on Thursday in the journal Current Biology, found these ancient people had significant contact with Native American populations hundreds of years before the first Westerners reached the island in 1722.
The Rapa Nui people created a unique culture best known for the 900 monumental head-and-torso stone statues known as moai erected around Easter Island. The culture flourished starting around 1200 until falling into decline by the 16th century.
Genetic data on 27 Easter Island natives indicated that interbreeding between the Rapa Nui and native people in South America occurred roughly between 1300 and 1500.
"We found evidence of gene flow between this population and Native American populations, suggesting an ancient ocean migration route between Polynesia and the Americas," said geneticist Anna-Sapfo Malaspinas of the Center for GeoGenetics at the University of Copenhagen, who led the study.
The genetic evidence indicates either that Rapa Nui people traveled to South America or that Native Americans journeyed to Easter Island. The researchers said it probably was the Rapa Nui people making the arduous ocean round trips.
"It seems most likely that they voyaged from Rapa Nui to South America and brought South Americans back to Rapa Nui and admixed with them," said Mark Stoneking, a geneticist with Germany's Max Planck Institute for Evolutionary Anthropology who collaborated on a related study of Brazil's indigenous Botocudo people. "So it will be interesting to see if in further studies any signal of Polynesian, Rapa Nui ancestry can be found in South Americans."
Climate windows for Polynesian voyaging to New Zealand and Easter Island
Authors:
Goodwin et al
Abstract:
Debate about initial human migration across the immense area of East Polynesia has focused upon seafaring technology, both of navigation and canoe capabilities, while temporal variation in sailing conditions, notably through climate change, has received less attention. One model of Polynesian voyaging observes that as tradewind easterlies are currently dominant in the central Pacific, prehistoric colonization canoes voyaging eastward to and through central East Polynesia (CEP: Society, Tuamotu, Marquesas, Gambier, Southern Cook, and Austral Islands) and to Easter Island probably had a windward capacity. Similar arguments have been applied to voyaging from CEP to New Zealand against prevailing westerlies. An alternative view is that migration required reliable off-wind sailing routes. We investigate the marine climate and potential voyaging routes during the Medieval Climate Anomaly (MCA), A.D. 800–1300, when the initial colonization of CEP and New Zealand occurred. Paleoclimate data assimilation is used to reconstruct Pacific sea level pressure and wind field patterns at bidecadal resolution during the MCA. We argue here that changing wind field patterns associated with the MCA provided conditions in which voyaging to and from the most isolated East Polynesian islands, New Zealand, and Easter Island was readily possible by off-wind sailing. The intensification and poleward expansion of the Pacific subtropical anticyclone culminating in A.D. 1140–1260 opened an anomalous climate window for off-wind sailing routes to New Zealand from the Southern Austral Islands, the Southern Cook Islands, and Tonga/Fiji Islands.
