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EASTER ISLANDS, Chile: Researchers have helped resolve the question of which plant foods Easter Islanders relied on, before European contact, by analyzing dental calculus from ancient teeth. The researchers are the first biological anthropologists to study dental calculus in the Pacific area.
Known to its Polynesian inhabitants as Rapa Nui, Easter Island is thought to have been colonized around the 13th century and is famed for its mysterious large stone statues or moai.
Monica Tromp, a PhD student of Anatomy at the University of Otago in New Zealand and Dr. John Dudgeon, assistant professor at the Department of Anthropology at Idaho State University, suggested that palm may have been a staple plant food for Rapa Nui’s population over several centuries. However, no other line of archaeological or ethno-historic evidence supports the fact that palm had a dietary role on Easter Island. In fact, evidence points to the fact that the palm tree became extinct soon after colonization.
Nevertheless, the researchers have found that the vast majority of phytoliths (plant microfossils) embedded within the calculus were from palm trees.
The examined teeth were taken from burials excavated in the early 1980s from multiple coastal archaeological sites around the island. The researchers undertook further analysis that included identifying starch grains in the dental calculus that were removed from the sample of 30 teeth.
After removing and decalcifying the plaque from each tooth, Tromp and Dudgeon identified starch grains that were consistent with modern sweet potato. None of the recovered grains showed any similarities to banana, taro or yam, other starchy plants that were hypothesized to have been part of the diet. The researchers went on to test modern sweet potato skins that are grown in sediment similar to that of Rapa Nui’s and found that as the tubers grow, their skins seem to incorporate palm phytoliths from the soil.
"This actually bolsters the case for sweet potato as a staple and important plant food source for the islanders from the time that the island was first colonized," Tromp said. "It is an excellent target for looking at the plant component of ancient diets, as microfossils become embedded in dental calculus throughout a person’s life. You can get a good idea of some of the plant foods people were eating, which is not an easy task. This research also shows that the plant foods you find evidence for in dental calculus can come from the environment that foods are grown in and not necessarily from the plant itself — this finding has the potential to impact dental calculus studies worldwide."
Determining plants’ roles in ancient Oceanic diets is extremely difficult due to the scarcity of plant remains. However, this research of microscopic plant remains is providing one more piece of the dietary puzzle.
The study, titled "Differentiating dietary and non-dietary microfossils extracted from human dental calculus: the importance of sweet potato to ancient diet on Rapa Nui", was published online ahead of the print article in the Journal of Archaeological Science.
