Easter island’s famous features, up to 33 feet large human figures carved from the local quarried volcanic rocks, have long puzzled visitors and scientists. When in 1786 a French expedition visited the island, almost sixty years after the discovery by Europeans, the artist Duché de Vancy depicted some of the monumental statues, called moai, still standing on their ahu, large stone platforms. Less than one hundred years later no upright statues were reported anymore, likely toppled by conflicts between the different clans and by “earth-shaking”, an earthquake or tsunami striking the island of volcanic origin.
The role of the moai in the culture of the ancient inhabitants of the island, the Rapa Nui people, is lost to history, as diseases and slave raiding caused the collapse of the formerly isolated society. The moai were likely not representations of aliens, as proposed by some authors, but may of ancestors. They were interpreted as holy sites to venerate the mana, the lifeforce of the ancestors, as burial sites or as symbolic guardians of the island. In any case, they were important enough to justify remarkable creative and physical feats to produce and transport more than 900 statues over a time-span of 600 years. Most moai seem to be located near the shores, facing towards the sea, and some authors suggested therefore that they acted as symbolic guardians and protectors of the island.
Research, published in the journal PLOS One, used computerized spatial analysis to study the locations of the 93 moai in the relationship with available resources of the island, like land to plant crops and sweet potatoes, fishing spots and springs with fresh water, discovering that they are usually located near sources of drinkable water.
Easter Island is a relatively barren place. The average annual rainfall is low and there are no reliable streams or springs with fresh water found on the island. On a small island, the groundwater table often coincides with the sea level. Rain infiltrates the porous volcanic rocks, flowing downwards it encounters a layer of seawater. Due to density differences, the two water types don’t mix. Instead, a layer of fresh water overlying the salty water forms. The drinkable water reemerges at the surface in areas along the coast or on the shelf of the island. Along the coast, there are caves with fresh water to be found. Especially inland statues were found to be situated near those caves. Most groundwater comes out from the ground in the intertidal zone, the area that is above water at low tide and underwater at high tide, surrounding the island. This drinkable water is only accessible during low tide and most of the studied ahu with moai on them are located within sight of these spots. The connection between the statues and the spots were groundwater was accessible suggest that they had, apart religious significance, also a quite practical use into the lives of the community. They were used to indicate or claim ownership of this spot and the nearby fresh water source.