Ancient Easter Islanders had a diet of mostly sweet potato (Ipomoea batatas) before European contact, according to researchers Dr John Dudgeon from Idaho State University and Monica Tromp from the University of Otago, New Zealand.
New research indicates the importance of sweet potato to the Easter Island diet prior to European contact in 1722. Image credit: Bjørn Christian Tørrissen / CC BY-SA 3.0.
The team has just published a new paper clearing up their previous puzzling finding that suggested palm may have been a staple plant food for Easter Islanders over several centuries.
However, no other line of archaeological or ethnohistoric evidence supports palm having a dietary role on the island.
In fact, evidence points to the palm becoming extinct soon after colonization.
Nevertheless, Dr Dudgeon and Ms Tromp had found that the vast majority of plant microfossils embedded within ancient dental calculus was from palm trees.
To clear up the mystery, they undertook further analysis, newly published in the Journal of Archaeological Science.
This included identifying starch grains in the dental calculus removed from 30 human teeth found at ten archaeological sites throughout Easter Island, dating between 1330–1900 CE.
After removing and decalcifying the plaque from each tooth, the scientists 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.
Next, the team went on to test modern sweet potato skins grown in sediment similar to that of Easter Island’s and found that as tubers grow, their skins seem to incorporate palm phytoliths from the soil.
“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,” Ms Tromp said.
“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 food itself – this finding has the potential to impact dental calculus studies worldwide.”
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