Easter Island is famous for its colossal stone heads, or moai, created by an ancient and nearly extinct people known as the Rapa Nui. One of the many mysteries surrounding the island has been uncovering exactly what happened to these people (which nearly destroyed their society). Scientists have recently found clues that could provide insight as to how this happened.
The Rapa Nui are estimated to have settled Easter Island around 1200 AD and had a population that peaked at around 15,000 people at its height. However, once Europeans settled there in the 1720s the population had dropped to only a few thousand, dropping to as low as just over 100 individuals in the 1860s. Since that time, the population has bounced back somewhat, with the 2002 Census indicating that there are about 2,220 Rapa Nui living on the island, mostly in one coastal village called Hanga Roa.
The question is: what caused this rapid decline in population? Theories abound, with ideas from climate change to overpopulation to the introduction of European people and diseases. “In the current Easter Island debate, one side says the Rapa Nui decimated their environment and killed themselves off,” says Oliver Chadwick, a professor in U.C. Santa Barbara’s Department of Geography and the Environmental Studies Program. “The other side says it had nothing to do with cultural behavior, that it was the Europeans who brought disease that killed the Rapa Nui. Our results show that there is some of both going on, but the important point is that we show evidence of some communities being abandoned prior to European contact.”
Chadwick was part of a team including archaeologists from Virginia Commonwealth, UC Davis and the University of Auckland that examined six different sites around the island. Using a method of analyzing obsidian (a naturally occurring volcanic glass), they were able to determine the amount of water that had penetrated its surface, which helped determine its age and how long it had been exposed. This gave them a starting point to determine trends in climate and soil chemistry on three particular sites.
The first site analyzed was near the northwest coast and had low rainfall but relatively high soil nutrient availability, due to the proximity of a volcano. The second site on the interior side of the volcanic mountain had high rainfall but low nutrient content. The third site however, another near-coastal zone in the northeast of the island, had decent amounts of rainfall and relatively high soil nutrients.
“When we evaluate the length of time that the land was used based on the age distribution of each site’s obsidian flakes, which we used as an index of human habitation, we find that the very dry area and the very wet area were abandoned before European contact,” Chadwick said. “The area that had relatively high nutrients and intermediate rainfall maintained a robust population well after European contact.”
The results have been published in the journal Proceedings of the National Academy of Sciences and they suggest that the population of the Rapa Nui was already in decline when the Europeans arrived and that they were simply attempting to react to their environmental challenges in order to grow crops and sustain their population rather than by negatively impacting the environment themselves.
Pretty amazing information to have been learned just from studying some glass and stones!
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