Interesting Science

Contents:

1) New Theory: "Rats, not men, to blame for death of Easter Island"
2) Video clip from the BBC series "State of the Planet"
3) NASA image and caption
4) Papers by Terry Hunt

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1) New Theory: "Rats, not men, to blame for death of Easter Island"

The Independent UK, January 2007: It was the first and most extreme ecological disaster. Easter Island, in the south Pacific, once lush with subtropical broadleaf forest, was left barren and vast seabird colonies were destroyed after the arrival of man.

But now there is new evidence that human beings may not have been responsible for the destruction after all. Although Easter Island has long been held to be the most important example of a traditional society destroying itself, it appears that the real culprits were rats - up to three million of them.

..."A theme of self-inflicted, pre-European contact ecocide is common in published accounts," says the anthropologist Dr Terry Hunt, who led the research at the University of Hawaii's Department of Anthropology.

Continued at "Rats, not men, to blame for death of Easter Island"

The above news report is based on the paper:

Rethinking Easter Island’s ecological catastrophe
Journal of Archaeological Science, Volume 34 (2007) 485 - 502
Terry L. Hunt
doi:10.1016/j.jas.2006.10.003

Abstract

Rapa Nui (Easter Island) has become a paragon for prehistoric human induced ecological catastrophe and cultural collapse. A popular narrative recounts an obsession for monumental statuary that led to the island's ecological devastation and the collapse of the ancient civilization. Scholars offer this story as a parable of today’s global environmental problems. In this paper, I review new and emerging Rapa Nui evidence, compare ecological and recently acquired palaeo-environmental data from the Hawaiian and other Pacific Islands, and offer some perspectives for the island's prehistoric ecological transformation and its consequences. The evidence points to a complex historical ecology for the island; one best explained by a synergy of impacts, particularly the devastating effects of introduced rats (Rattus exulans). This perspective questions the simplistic notion of reckless over-exploitation by prehistoric Polynesians and points to the need for additional research. [Archaeology]

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2) Video clip from the BBC series "State of the Planet"

The clip begins with Edward O. Wilson ("We have to learn a new ethic that allows us to care as much about the Brazilian rainforest as our own local reserve..") and continues with David Attenborough ("A warning on what the future could hold..") narrating the 'current opinion' on the causes of Easter Island's ecological disaster:

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3) NASA image and caption (Large Image)

Landsat 7's Enhanced Thematic Mapper Plus (ETM+) instrument collected this image of the island on January 3, 2001 and is titled "Easter Island (Rapa Nui)"

Accompanying text:

On Easter Sunday in 1722, a Dutch explorer sailing in the vast and nearly landless waters of the South Pacific Ocean came upon a small island, alone in more than 8.5 million square miles of sea. In honor of the religious holiday, the explorer, Jacob Roggeveen, called the lonely spot Easter Island. Today, the native people call the island Rapa Nui, but the oldest known name appears to be Te Pito o Te Henua, or "The Center (or Navel) of the World."

When the Dutch sailors arrived, the isolated island had already been inhabited for more than one thousand years, most likely settled by Polynesian sailors in canoes between 400 and 700 A.D. The most amazing cultural artifacts on display were giant stone statues, called moai, resting on ahu, a raised platform of expertly fitted stones. (Ahu also describes a sacred ceremonial site where several moai stand.)

Most of the hundreds of moai on the island were carved out of volcanic rock in the crater of Rano Raraku, located in the southeastern part of the island. In addition to the hundreds of moai located at ahu around the island, Rano Raraku is littered with moai, some only half-carved, others that appear to have broken in the attempt to remove them from the quarry, and still others that seem to simply have been abandoned.

East of Rano Raraku is Ahu Tongariki, where in 1960 a tidal wave caused by an earthquake in Chile struck the southern coastline and swept 15 moai inland for several hundred feet. In 1992, the site was restored by a Chilean archeologist. On the western end of the island is the only town, Hanga Roa, where most of Rapa Nui's 2,000 residents live. South of the town is the island's largest volcanic crater, Rana Kao. Along the crater rim looking southward over the coast, lie the ruins of Orongo, a ceremonial site containing elaborate stone carvings and other artwork.

Speculation about how the island's inhabitants built and moved the massive moai to ahu all along the coastline and at various sites in the island's interior has fueled scientific imagination and controversy that goes on today. Several experiments (see Thor Heyerdahl's The "Walking" Moai of Easter Island from Norway's Kon-Tiki Museum) have been carried out using materials that would have been available to the inhabitants, and most scientists agree that any method they might have used would have required a large amount of wood and wood fiber: to construct sleds or other sliding platforms, to make ropes, and to create levers to help position the statues.

The demand for wood eventually stripped the island of nearly all its forests, and when the lush palm forests disappeared, the topsoil began to erode. Crops failed and archeological and anthropological evidence suggests violent civil wars and perhaps even cannibalism preceded the collapse of Rapa Nui's first civilization. The loss of wood guaranteed the inhabitant's isolation for hundreds of years. The islanders were unable to build canoes. After hundreds of years of isolation, the arrival of the Dutch sailors was probably as surprising to the native islanders as the discovery of a populated island in such a remote location was to the Europeans.

Source: NASA's Earth Observatory - To locate the page, enter "Rapa Nui" (rather than "Easter Island") into the search box. At the time of writing, the image is located on Page 76 but this will change as new items are added.

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4) Papers by Terry Hunt:

Ancient DNA of the Pacific rat (Rattus exulans) from Rapa Nui (Easter Island)
Journal of Archaeological Science, Volume 33, Issue 11, November 2006, Pages 1536-1540
S.S. Barnes, E. Matisoo-Smith and T.L. Hunt
doi: 10.1016/j.jas.2006.02.006

Abstract

We report analysis of ancient mitochondrial DNA sequences from nine archaeological specimens (8 femura and 1 incissor) of Rattus exulans excavated from Anakena Beach Dune on Rapa Nui. Sequence of a 239-base-pair fragment of the hypervariable mitochondrial control region reveals a single mitochondrial DNA (mtDNA) sequence of all samples corresponding to the R9 haplotype prevalent in East Polynesia. This suggests a single or very limited introduction of Rattus exulans to the island. Rapa Nui, like other remote islands of Polynesia, remained effectively isolated following colonization.

Rethinking the Fall of Easter Island: New evidence points to an alternative explanation for a civilization's collapse.
American Scientist 94:412-419.
Volume 94, Number 5 September-October 2006

Every year, thousands of tourists from around the world take a long flight across the South Pacific to see the famous stone statues of Easter Island. Since 1722, when the first Europeans arrived, these megalithic figures, or moai, have intrigued visitors. Interest in how these artifacts were built and moved led to another puzzling question: What happened to the people who created them?

In the prevailing account of the island's past, the native inhabitants - who refer to themselves as the Rapanui and to the island as Rapa Nui - once had a large and thriving society, but they doomed themselves by degrading their environment. According to this version of events, a small group of Polynesian settlers arrived around 800 to 900 A.D., and the island's population grew slowly at first. Around 1200 A.D., their growing numbers and an obsession with building moai led to increased pressure on the environment. By the end of the 17th century, the Rapanui had deforested the island, triggering war, famine and cultural collapse.

Jared Diamond, a geographer and physiologist at the University of California, Los Angeles, has used Rapa Nui as a parable of the dangers of environmental destruction. "In just a few centuries," he wrote in a 1995 article for Discover magazine, "the people of Easter Island wiped out their forest, drove their plants and animals to extinction, and saw their complex society spiral into chaos and cannibalism. Are we about to follow their lead?" In his 2005 book Collapse, Diamond described Rapa Nui as "the clearest example of a society that destroyed itself by overexploiting its own resources."

...Diamond is certainly not alone in seeing Rapa Nui as an environmental morality tale.

Late Colonization of Easter Island
Terry L. Hunt and Carl P. Lipo

Originally published in Science Express on 9 March 2006
Science 17 March 2006:
Vol. 311. no. 5767, pp. 1603 - 1606
DOI: 10.1126/science.1121879

Easter Island (Rapa Nui) provides a model of human-induced environmental degradation. A reliable chronology is central to understanding the cultural, ecological, and demographic processes involved. Radiocarbon dates for the earliest stratigraphic layers at Anakena, Easter Island, and analysis of previous radiocarbon dates imply that the island was colonized late, about 1200 A.D. Substantial ecological impacts and major cultural investments in monumental architecture and statuary thus began soon after initial settlement.

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