© Andia/UIG via Getty ImagesResearchers say Easter Island's statues were situated near sources of fresh water.
When it comes to Easter Island's towering stone heads, there's now one fewer mystery to solve.
Researchers have long puzzled over why the huge statues were placed where they are. However, a new study says the people of Rapa Nui, as the island is called in the local language, positioned them near sources of humanity's most vital resource: fresh water.
Archaeologists studied the location of the statues, or moai, and the platforms on which many of them stand, known as ahu. Polynesian seafarers first arrived on Rapa Nui, 2,300 miles off the coast of Chile, approximately 900 years ago.
They then went on to construct more than 300 ahu and almost 1,000 moai, which are believed to represent significant ancestors.
The authors of the new study, published in the journal PLOS One, isolated an eastern area of Rapa Nui, containing 93 ahu. Researchers from six US institutions analyzed the natural resources near the ahu, focusing on rock mulch gardens in which crops like sweet potatoes were grown, marine resources including sites for fishing, and sources of fresh water.
There proved to be no significant correlation between the location of the ahu and the presence of nearby gardens, suggesting that the ahu were not situated in order to monitor or signal control over these resources.
While both marine resources and fresh water sources were found near the ahu, the researchers concluded only the latter was significant; after all, both typically occur in the same locations and fresh water was much less widely available.
According to the study's authors, the availability of fresh water probably explains why most of the island's statues are situated near the coast. "One of the most abundant sources of freshwater, coastal seeps, occurs primarily in coastal locations," they wrote. The location of inland monuments could also be explained by their proximity to fresh water sources.
The findings suggest that Rapa Nui's moai and ahu were valuable beyond their ancestral significance, the study authors concluded.
"If Rapa Nui's monuments did indeed serve a territorial display function," they wrote, "then their patterns are best explained by the availability of the island's limited freshwater."