A Rapa Nui Rock Garden, or agricultural field, with Poike volcano in the background. Credit: Christopher M. Stevenson

(Phys.org)—A team of researchers with members from the U.S., Chile and New Zealand has uncovered evidence that contradicts the conventional view of the demographic collapse of the Rapa Nui people living on Easter Island, both before and after European contact. In their paper published in Proceedings of the National Academy of Sciences, the team describes how they conducted obsidian hydration dating of artifacts from the island to trace the history of human activity in the area and what they found in doing so.

For many years, Earth scientists and others have used Easter Island and its inhabitants, the Rapa Nui, as a lesson in what can happen when a parcel of land is overpopulated and thus overused—resources diminish and the people starve to death (or resort to cannibalism as some have suggested). But now, the researchers with this new effort suggest that thinking may be wrong.

Scientists believe Polynesians first settled on Easter Island sometime around 1200 AD—over the course of the next several hundred years the settlers became the Rapa Nui, famous for the massive maoi statues that were erected. Over that time period, the people cut down most of the trees on the northern part of the island and a lot of the other vegetation. That led to the loss of nutrient rich topsoil due to erosion and the idea that the people began to starve to death.

To better understand what actually occurred both before and after Europeans arrived in the 1700's, the researchers used a technique known as obsidian hydration dating on artifacts found at various sites on the northern part of the island where the Rapa Nui lived. That allowed them to gain insights into how the land in that area had been used during different time periods. From that they were able to construct a timeline that showed where the people were living over the course of hundreds of years. And that, the researchers report, showed that rather than a population crash due to starvation, there were population shifts that reflected changing weather patterns. Some areas did see population losses before European contact, and some actually saw initial gains afterwards. The population did see a dramatic decline, of course, sometime thereafter as the Rapa Nui people became exposed to European diseases such as smallpox and syphilis and as many were taken and sold into slavery. This means, the team concludes, that there is little evidence of population collapse prior to European contact.

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More information: Variation in Rapa Nui (Easter Island) land use indicates production and population peaks prior to European contact, Christopher M. Stevenson, PNAS, DOI: 10.1073/pnas.1420712112 Variation in Rapa Nui (Easter Island) land use indicates production and population peaks prior to European contact, Christopher M. Stevenson, Abstract

Many researchers believe that prehistoric Rapa Nui society collapsed because of centuries of unchecked population growth within a fragile environment. Recently, the notion of societal collapse has been questioned with the suggestion that extreme societal and demographic change occurred only after European contact in AD 1722. Establishing the veracity of demographic dynamics has been hindered by the lack of empirical evidence and the inability to establish a precise chronological framework. We use chronometric dates from hydrated obsidian artifacts recovered from habitation sites in regional study areas to evaluate regional land-use within Rapa Nui. The analysis suggests region-specific dynamics including precontact land use decline in some near-coastal and upland areas and postcontact increases and subsequent declines in other coastal locations. These temporal land-use patterns correlate with rainfall variation and soil quality, with poorer environmental locations declining earlier. This analysis confirms that the intensity of land use decreased substantially in some areas of the island before European contact. Journal information: Proceedings of the National Academy of Sciences

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