Ancient dental plaque reveals Easter Islanders' diet

A University of Otago research team from New Zealand analysing dental calculus (hardened plaque) from ancient teeth is helping resolve the question of what plant foods Easter Islanders relied on before European contact.

Known to its Polynesian inhabitants as Rapa Nui, Easter Island is thought to have been colonised around the 13th century.

Earlier, it was thought that the palm may have been the staple plant food for Rapa Nui's population over several centuries.

But this was not substantiated by any other archaeological or ethnohistoric evidence

Now, researchers have studied the teeth collected from multiple coastal burial sites around the island.

This included identifying starch grains in the dental calculus removed from 30 teeth.

After removing and decalcifying the plaque from each tooth, researchers identified starch grains that were consistent with modern sweet potato.

"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 colonised," said Monica Tromp, an anatomy student from the Idaho State University in the US.

Monica Tromp and Idaho State University's John Dudgeon are the first biological anthropologists to study dental calculus in the Pacific.

They tested modern sweet potato skins grown in sediment similar to that of Rapa Nui's and found that as tubers grow, their skins seem to incorporate palm phytoliths from the soil.

The finding has the potential to impact dental calculus studies worldwide.

This research on microscopic plant remains is providing one more piece of the dietary puzzle since determining plants' role in ancient Oceanic diets is extremely difficult due to the scarcity of plant remains, the team said.

The study appeared in the Journal of Archaeological Science.