Few places on Earth generate as much ink as Easter Island, also known as Rapa Nui. The tiny, 63 square mile island is one of the most recently formed places on Earth to be inhabited and even without its well known statues, it is rife with scientific, historical and cultural mysteries.

Theories about when, exactly, the native population of the island settled there range from 300 CE to 1200 CE. Researchers also aren’t sure where the population came from, because the only known inhabited areas are more than 2000 miles away. It is also unclear what happened to the local population.

Some have argued that the arrival of Europeans, along with disease, invasive species and the slave trade doomed the population. Others believe that environmental degradation doomed the population before the arrival of Europeans. Given that it was a recently formed volcanic island it is likely that Rapa Nui was extremely environmentally sensitive to begin with.

“Sometime before the arrival of Europeans on Easter Island, the Rapanui experienced a tremendous upheaval in their social system brought about by a change in their island’s ecology… By the time of European arrival in 1722, the island’s population had dropped to 2,000–3,000 from a high of approximately 15,000 just a century earlier.” said Barbara A. West in Encyclopedia of the Peoples of Asia and Oceania.

A new study published in the Proceedings of the National Academy of Sciences suggests that the population was in steep decline before the arrival of Europeans. The problem may not have been environmental, however, but the constraints of living on a 63 square mile island.

“The results of our research were really quite surprising to me. Indeed, in the past, we’ve published articles about how there was little evidence for pre-European-contact societal collapse,” study co-author Thegn Ladefoged, an anthropologist at the University of Auckland in New Zealand, told Live Science.

In an attempt to understand and clarify the Easter Island timeline, the researchers analyzed more than 400 obsidian artifacts from six sites around the island. The team focused primarily on three sites where good information was available on soil chemistry and historic climate.

Because obsidian absorbs water after being exposed to air, the researchers were able to measure the amount of water in the obsidian and determine when they were made. The scientists were then able to estimate population increases and declines based on the number of tools made during each period.

The first site, on the northwest coast, showed an increase in population between 1220 and 1650 and then a rapid decline. This site was also prone to drought because of its location in the rain shadow of the Ma’unga volcano.

The second site on an interior mountainside was wetter and less prone to drought but would have had low soil fertility. The site showed an increase in use from 1200 to 1480 and steady use until 1705 before beginning to decline.

The third site, both rainy and fertile, showed an increase in use starting about 1250 and then fairly constant use until 1850.

Because Europeans didn’t arrive until 1722 the first two sites show that something was going wrong before their arrival. Researcher believe that the Rapa Nui people were struggling against the natural limitations of the islands ecology rather than environmental degradation.

“It is clear 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,” said Ladefoged.

As research on the island continues, Ladefoged hopes to examine individual dwellings to understand the interaction between Easter Islands aboriginal people and their environment.