Dental plaque reveals key plant in prehistoric Easter Island diet

A student analyzing dental calculus from ancient teeth is helping resolve the question of what plant foods Easter Islanders relied on before European contact. Otago Anatomy PhD student Monica Tromp and Idaho State University’s Dr John Dudgeon have just published new research clearing up their previous puzzling finding that suggested palm may have been a staple plant food for Rapa Nui’s population over several centuries. However, no other line of archaeological or ethnohistoric evidence supports palm having a dietary role on Easter Island; in fact evidence points to the palm becoming extinct soon after colonization. Nevertheless, the researchers had found that the vast majority of phytoliths (plant microfossils) embedded within the calculus were from palm trees. The teeth were from burials excavated in the early 1980s from multiple coastal archaeological sites around the island. After removing and decalcifying the plaque from each tooth, Ms Tromp and Dr 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 are hypothesised to be part of the diet. So this actually bolsters the case for sweet potato as a staple and important plant food source for the Islanders from the time the island was first colonized. 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.