Rapa Nui Mystery Unraveled


Judy Lau
Staff Writer

A new study conducted by a group of researchers, including University of California, Santa Barbara’s Oliver Chadwick, offers a different explanation regarding the decline of the Rapa Nui Society. Their work shows that the demise of the Rapa Nui culture began prior to European settlement.

Long before Europeans arrived on Easter Island in 1722, the native Polynesian culture known as Rapa Nui showed signs of decline. However, the catalyst for their decline has long been debated in the scientific community as to whether the problem was environmental, political, or disease-related.

Chadwick joined archaeologists Cedric Puleston of the University of California, Davis, Thegn Ladefoged of the University of Auckland, and Christopher Stevenson of Virginia Commonwealth University in examining six agriculture sites used by the island’s inhabitants. The research focused on the three sites they had information on regarding climate, land, and soil chemistry.

“In the current Easter Island debate, one side says the Rapa Nui decimated their environment and killed themselves off,” said Chadwick, a professor in UCSB’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.”

The team used flakes of obsidian, a natural glass, as a dating tool. They measured the amount of water that penetrated the obsidian’s surface, allowing them to see how long it had been exposed and determine its age.

The study reflected the environmental diversity of Easter Island, located 2300 miles off the west coast of Chile. The soil nutrient supply on Easter Island is less than some of the Hawaiian Islands, which were settled on by the Polynesians around the same time.

The first site the researchers analyzed was near the northwest coast, and it had low rainfall and high soil nutrient availability. The second site, which was located on the inside of the volcanic mountain, experienced high rainfall but had low nutrient supply. The third location, which was another coastal area near the northeast, had intermediate amounts of rainfall and 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.”

These results suggest that the Rapa Nui had produced sufficient crops rather than degrading the environment themselves, due to the regional variations and natural environmental factors. Where they produced food well, they were able to maintain their culture despite the threat of external factors from European diseases such as: tuberculosis, syphilis, and smallpox.

“The pullback from the marginal areas suggests that the Rapa Nui couldn’t continue to maintain the food resources necessary to keep the statue builders in business,” Chadwick concluded. “So we see the story as one of pushing against constraints and having to pull back rather than one of violent collapse.”