Easter Island Mystery revealed using mathematical model
Rhett A. Butler, mongabay.com
September 1, 2005
Jared Diamond, a professor of geography and physiology at UCLA, has explored the mysterious demise of the people of Easter Island, one of the most isolated places on Earth. Now a new study from the Rochester Institute of Technology models the collapse of this once mighty society. Below you will find an overview of Easter Island from Jared Diamond's Guns, Germs, and Steel and his later work, Collapse: How Societies Choose to Fail or Succeed, followed by an overview by NASA and a press release on the new mathematical modeling by William Basener, assistant professor of mathematics at the Rochester Institute of Technology.
When Easter Island was "discovered" by Europeans in 1722, it was a barren landscape with no trees over ten feet in height. The small number of inhabitants, around 2000, lived in a state of civil disorder and were thin and emaciated. Virtually no animals besides rats inhabited the island and the natives lacked sea-worthy boats. Understandably, the Europeans were mystified by the presence of great stone statues, some as high as 33 feet and weighing 82 tons. Even more impressive were the abandoned statues-as tall as 65 feet and weighing as much as 270 tons. How could such a people create, and then move such enormous structures? The answer lies in Easter islands' ecological past, when the island was not a barren place.
It was this Easter Island society that built the famous statues and hauled them around the island using wooden platforms and rope constructed from the forest. The construction of these statues peaked from 1200 to 1500 AD, probably when the civilization was at its greatest level. However, pollen analysis shows that at this time the tree population of the island was rapidly declining as deforestation took its toll.
Around 1400 the Easter Island palm became extinct due to overharvesting. Its capability to reproduce has become severely limited by the proliferation of rats, introduced by the islanders when they first arrived, which ate its seeds. In the years after the disappearance of the palm, ancient garbage piles reveal that porpoise bones declined sharply. The islanders, no longer with the palm wood needed for canoe building, could no longer make journeys out to sea. Consequently, the consumption of land birds, migratory birds, and mollusks increased. Soon land birds went extinct and migratory bird numbers were severely reduced, thus spelling an end for Easter Island's forests. Already under intense pressure by the human population for firewood and building material, the forests lost their animal pollinators and seed dispersers with the disappearance of the birds. Today, only one of the original 22 species of seabird still nests on Easter Island.
With the loss of their forest, the quality of life for Islanders plummeted. Streams and drinking water supplies dried up. Crop yields declined as wind, rain, and sunlight eroded topsoils. Fires became a luxury since no wood could be found on the island, and grasses had to be used for fuel. No longer could rope by manufactured to move the stone statues and they were abandoned. The Easter Islanders began to starve, lacking their access to porpoise meat and having depleted the island of birds. As life worsened, the orderly society disappeared and chaos and disarray prevailed. Survivors formed bands and bitter fighting erupted. By the arrival of Europeans in 1722, there was almost no sign of the great civilization that once ruled the island other than the legacy of the strange statues. However, soon these too fell victim to the bands who desecrated the statues of rivals.
Easter Island is a prime example of what widespread deforestation can do to a society. As the forests are depleted, the quality of life falls, and then order is lost. The example of Easter Island should be enough for us to reconsider our current practices.
Image and text below courtesy of NASA Earth Observatory
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 or 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 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.
Landsat 7's Enhanced Thematic Mapper Plus (ETM+) instrument collected this image of the island on January 3, 2001.
NASA image created by Jesse Allen, Earth Observatory, using data obtained from the University of Maryland's Global Land Cover Facility.
Groundbreaking Research Sheds Light on Ancient Mystery
RIT researcher creates new population model to help predict and prevent societal collapse
Modified Rochester Institute of Technology release
Between 1200 and 1500 A.D., the small, remote island, 2,000 miles off the coast of Chile, was inhabited by over 10,000 people and had a relatively sophisticated and technologically advanced society. During this time, inhabitants used large boats for fishing and navigation, constructed numerous buildings and built many of the large statues, known as Tiki Gods, for which the island is now best known. However, by the late 18th century, when European explorers first discovered the island, the population had dropped to 2,000 and islanders were living in near primitive conditions, with almost all elements of the previous society completely wiped out.
"The reasons behind the Easter Island population crash are complex but do stem from the fact that the inhabitants eventually ran out of finite resources, including food and building materials, causing a massive famine and the collapse of their society," Basener says. "Unfortunately, none of the current mathematical models used to study population development predict this sort of growth and quick decay in human communities."
Population scientists use differential equation models to mimic the development of a society and predict how that population will change over time. Since incidents like Easter Island do not follow the normal progression of most societies, entirely new equations were needed to model the outcome. Computer simulations using Basener's formula predict values very close to the actual archeological findings on Easter Island. His team's results were recently published in SIAM Journal of Applied Math.
Basener will next use his formula to analyze the collapse of the Mayan and Viking populations. He also hopes to modify his work to predict population changes in modern day societies.
"It is my hope this research can be used to create a better understanding of past societies," Basener adds. "It will also eventually help scientists and governments develop better population management skills to avert future famines and population collapses."
Basener's research was done in collaboration with David Ross, visiting professor of mathematics at the University of Virginia, mathematicians Bernie Brooks, Mike Radin and Tamas Wiandt and a group of RIT mathematics students.
Modified Rochester Institute of Technology release
Guns, Germs, and Steel
Collapse: How Societies Choose to Fail or Succeed