The mysteries of Rapa Nui – or Easter Island – have puzzled explorers, tourists and scientists for centuries. When was it first settled? Where did the settlers come from? How did they carve and move the moai – the giant statues they carved from volcanic rock? What did these figures represent? And what became of these people and their culture – which had dwindled so dramatically by the time the Europeans came across this remote yet inhabited island? Over the years, theories have been vigorously asserted then replaced by the discovery and interpretation of new evidence.

Easter Island has been used in the past as the poster child for what happens when a population over-exploits its environment. Now a team of scientists led by University of Auckland’s Professor Thegn Ladefoged has put forth a new hypothesis based on the analysis of approximately 400 obsidian artifacts they recovered at six different sites.

Focusing on just three of the sites where the artifacts were abundant and where they had good information on soil chemistry and climate conditions, Ladefoged and his team were able to estimate when the artifacts were created (based on the amounts of water the obsidian had absorbed), and populations fluctuations (based on the number of artifacts that they found at each site).

From this evidence they estimate that all three sites were settled sometime in the 13th century. One site showed a growth in population until the mid-17th century – followed by a sharp decline. Another site endured till the early 18th century. And the third site, which had the advantages of being both rainy and fertile, showed fairly constant use till the mid-19th century.

Reporting in the on-line journal, The Proceedings of the National Academy of Sciences, the scientists concluded that “… people were reacting to regional environmental variation on the island before they were devastated by the introduction of European diseases and other historic processes.” The team believes the shifts in land use and population were in response to the constraints placed upon them by the small, isolated island.