Back An archaeological study involving UPF makes new finds on Easter Island

An archaeological study involving UPF makes new finds on Easter Island

A study published in The Holocene has found pigment production pits subsequent to the island’s deforestation, thus disproving the alleged social collapse thought to have led to the clearance of vegetation. A team of researchers associated with institutions in Denmark, Germany and Spain, has discovered an innovative vision of prehistoric pigment production technology. Marco Madella, ICREA-UPF research professor and co-author of the article, has worked on the analysis of phytoliths, which has been jointly conducted by the UPF’s environmental archaeology laboratory and Moesgaard Museum.


Imatge inicial

New archaeological finds and scientific analyses shed light on the prehistory of Easter Island (Rapa Nui), located in Chilean Polynesia, in the south-eastern Pacific Ocean. An international team of scientists, including environmental archaeologists, geoarchaeologists and paleoecologists, linked to Moesgaard Museum in Denmark, Kiel University in Germany, along with the CREAF (Ecological Research and Forestry Applications Centre) and Pompeu Fabra University in Barcelona, has discovered and investigated pits (dating from the 13th to the 17th centuries) used for the production and storage of red pigment on Easter Island.

"From the environmental archaeology laboratory of the Department of Humanities at UPF we have analyzed samples coming from the deposits of the pits".

The scientists found that the production of reddish pigment was an important activity on Easter Island and that prehistoric peoples continued with the production of these pigments, thus maintaining important aspects of the inhabitants’ cultural life, despite the drastic changes to the island’s ecosystem and environment. An earlier hypothesis presented by Jared Diamond in the book Collapse (2005) assumed that the clearance of vegetation, related to the overpopulation of the island, led to erosion, scarce resources and food, and ultimately to cultural collapse. The new data, however, presented in the journal “The Holocene”, suggest a different story.

Easter Island is famous for its archaeology and particularly for its large, human-looking statues, the Moai. However, its inhabitants also produced reddish pigments. Red ochre is considered sacred on the island and was used in rock paintings, petroglyphs, Moai and in archaeological burial contexts. While the presence of the pigment was already well known, the source and possible production process were not well understood.

How were the pigments found in the pits produced?

In recent years, the research team has carried out excavations and scientific analyses on newly discovered pits. The pits containing red pigment were excavated by Kiel University in four different places and document for the first time the large-scale production of pigment on the island.

The findings have also provided a completely new understanding of prehistoric pigment production technology. The pits were rich in very fine particles of hematite and maghemite iron oxides, which are bright red in colour. Geochemical, microcharcoal and phytolith analyses indicate that the minerals were heated, possibly to achieve a brighter colour. Some of the pits were covered with a lid, which indicates that they were used both for production and for storing pigments.

“We have analysed samples taken from the pits at the environmental archaeology laboratory of the Department of Humanities at UPF”.

Moesgaard Museum directed the analysis of phytoliths (microscopic plant opals) and diatoms (microscopic algae) from the pits on Easter Island. The analysis of phytoliths was carried out in collaboration with Pompeu Fabra University, while diatom analysis was conducted by the CREAF. Phytoliths are microscopic silica bodies formed within and between plant cells and cell walls of living plants.

Marco Madella, co-author of the article, ICREA-UPF research professor at the Department of Humanities and coordinator of the UPF Culture and Socio-Ecological Dynamics (CaSEs) research group, explains the work to which the University has contributed: “We have analysed samples taken from the pits at the environmental archaeology laboratory of the Department of Humanities at UPF, and they have helped us to understand how these pigments were produced”.

Use of grasses to heat the pigments and adaptation to new environmental conditions

The phytoliths found in the Easter Island pits come mainly from plants of the Panicoideae subfamily of grasses. The presence of grass is interpreted as part of the fuel used to heat the pigment. The analysis of both phytoliths and diatoms disproves a previous theory that held that the people used the roots of a wetland plant found in the island’s crater lakes as fuel. In addition, the diatoms are not fused, indicating that they colonized the pits only after the pigment was deposited and subjected to heating in these holes.

The pits investigated on Easter Island date from between 1200 and 1650 AD (after the onset of the deforestation of the island and before the arrival of the first Europeans), and are located in Vaipú East, where most pits were found, some of which were located on top of palm root casts. This indicates that pigment production took place after the clearing and burning of palm vegetation. Also in another part of the island, Poike, a pit was found on top of palm root casts.

This indicates, that even though palm vegetation had disappeared, the prehistoric population of Easter Island continued to produce pigment, and on a substantial scale. This is in contrast to the earlier hypothesis that the clearance of the vegetation results in a societal collapse. “While Diamond’s assertion for sustainability remains absolutely relevant, our findings give us new knowledge about the flexibility of human groups to cope with changing environmental conditions”, says archaeobotanist Welmoed Out, of the Department of Archaeological Science and Conservation at Moesgaard Museum, who, in collaboration with UPF, has led the analysis of phytoliths from Easter Island.

What can the analysis of phytoliths reveal?

Phytolith analysis belongs to the field of archaeobotanics. Phytoliths are one of several types of plant remains that can be found at archaeological digs, and can be used to reconstruct how people used plants in the past. Other archaeobotanical remains include seeds and fruits, wood and charcoal, pollen and starch. One advantage of phytoliths is that these inorganic mineral particles remain well preserved in a wide range of conditions, even when exposed to temperatures up to 900°C.

In addition, phytoliths can provide new information to supplement the results of the analysis of other botanical remains, even when organic remains are preserved. This is due to the fact that phytoliths represent all types of plant parts, including delicate parts like straw, leaves and cane, almost undetectable in archaeological sites when other methods are used. Depending on the group found, the preservation and availability of a regional reference collection, phytoliths can be identified at family, subfamily, genus and species levels.

Reference article:

Out W., Mieth A., Pla-Rabés, S., Madella M., Khamnueva-Wendt S., Langan C., Dreibrodt S., Merseburger S., Hans-Rudolf B. (December 2020). “Prehistoric pigment production on Rapa Nui (Easter Island), c. AD 1200–1650: New insights from Vaipú and Poike based on phytoliths, diatoms and C dating”. The Holocene



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