A recent study has demonstrated that the work done in the quarry at Rano Raraku, where some thousand moai (statues) were carved from the years 1455-1605 AD, had also enriched the soil with phosphorus and other minerals, improving the conditions for cultivating domestic plants, such as the sweet potato, taro, manioc, gourds, mahute (paper mulberry), bananas and other food species.
Rano Raraku, the quarry of the moai, covers 126,741 m2 (31.3 acres) and is the site of production of the greatest amount of the stone statues known as moai. It contains 809 archaeological remains. Of these, only 59.7 % are moai; the rest is made up of foundations of houses (hare vaka), cooking areas (umu pae), petroglyphs and structures of rock gardens. “This tells us that in this place there were habitations, tools were produced, plants were raised and ceremonies, including funerals, were held,” indicates the archaeologist Jo Anne van Tilburg, who, in 2010, with students and members of the Rapanui community, began the Easter Island Project (EISP), a program of archaeological research in the crater of Rano Raraku.
Within the excavations, a completely new sculpture was discovered at five meters (16.5 feet) depth (moai RR-0001-156) on the interior slope of Rano Raraku. According to Van Tilburg, this statue was erected in a deep hole on a papa, a solid stone base, and held in place by a large stone of a meter (slightly over one yard) in height. This corresponds to the system of engineering utilized by the ancient sculptors when they placed a statue in its definitive location. In addition, they found firm evidence that another, older quarry lay underneath this bedrock. This discards previous theories that all the statues on the slopes of Rano Raraku were raised in order to later finish them and move them away. The paradigm was altered when it was determined that these statues were found there because the quarry at Rano Raraku was an important sacred site and not just a place for the production of statues.
“All the plants with domestic use were introduced by the Polynesian settlers, which implied the transport and adaptation of tropical species to a small, isolated island with a sub-tropical climate. We don’t know how long it took with this process of colonization to be able to maintain a highly hierarchical society with chiefs, priests and a variety of specialists with an intensive agriculture based on tubers,” explains José Miguel Ramirez-Aliaga of the Universidad de Playa Ancha in Valparaiso, who formed part of an international team led by Sara Sherwood of the Department of Earth and Environmental Systems at Sewanee: The University of the South (Tennessee) and which found a horticultural site on the southern and eastern interior slopes of Rano Raraku, which functioned from the XIVth Century until the early XIXth Century.
“During this period of socio-political transformation and of changes in the use of the land throughout the Island, vegetable plots were developed in rock gardens, a technique which required an intense use of manual labor to increase productivity while the fertility of the soil diminished within a period of deforestation and drought, as a result of possible climatic changes. Affected by a prolonged drought, the Islanders developed agricultural techniques to protect and maintain production through the construction of manavai (circular stone planter boxes of approximately 1 m in height) to protect the plants from the wind and rock gardens to hold the humidity in the soil for the cultivation of tubers. This happened while they were developing the ritual of Orongo with an intense focus on fertility”, concludes Van Tilburg.
The current study was concentrated on the moai RR-0001-156 of the Easter Island Project, one of the only three figures on the entire island that we know was adorned with a dense set of cohesive petroglyph motifs, and which we suppose was placed for ceremonial reasons in a productive site. Rano Raraku had (and still has) extremely fertile soils which are a sub-product of the erosion of the sediments of lapilli tuff that were generated by the process of extraction and the localized human activity. This study reaffirms Ranu Raraku as the principal center for production of moai, establishing chronological parameters for the statue RR-0001-156 and describes the agricultural fertility, offering a hypothesis of a rich scenery and multiple uses of the interior slopes of the quarry which have no parallel in other places on Rapa Nui.
The study, based on the chemistry of the soil, the micro-morphology and the macro- and micro-botanical data, within a model of Baysian inference and backed up by radiocarbon dating, the first of its kind on Rapa Nui, was done by Sherwood SC, Van Tilburg JO, Barrier CR, Horrocks M, Dunn RK and Ramírez-Aliaga JM. Soon to be published is a new study on the meaning of the complex petroglyphs found on the two moai recently excavated at the quarry of Rano Raraku and those which are on the moai Hoa Hakananai’a which was found at Orongo.