Stones challenge dating of Easter Island collapse

Easter Island’s farming society reorganized rather than collapsing before Europeans arrived in 1722, a new study suggests.

Residents of Easter Island, also known as Rapa Nui, sharply reduced farming at two previously thriving settlements decades before European explorers showed up, say archaeologist Christopher Stevenson of Virginia Commonwealth University in Richmond and his colleagues. One outpost near the coast received little rainfall and probably faced food shortages due to periodic droughts, instigating a farming decline that began around 1660, the scientists propose January 5 in the Proceedings of the National Academy of Sciences. After plentiful rain enabled farming to expand at an inland site starting around 1200, poor-quality soil triggered cultivation cutbacks starting around 1705 or 1710, they say.

Farming boomed in another part of the island, which had regular rainfall and relatively good soil, from the late 1600s to at least 1850, Stevenson’s team reports. Other evidence also suggests Rapa Nui farming continued after Europeans arrived (SN: 1/25/14, p. 9).

The researchers tracked farming patterns first by dating 286 obsidian artifacts — mostly tools for farming and other daily activities — from the three sites, using a technique based on the rate at which obsidian absorbs water. Stevenson and colleagues then examined whether numbers of artifacts increased or decreased over time and how those changes corresponded to historical rainfall and temperature shifts.