And research by University of Otago anatomy PhD student Monica Tromp suggests some big puzzles could be solved by brushing up on our knowledge of dental calculus, which is hardened plaque.
United States-born, Ms Tromp has been analysing dental calculus from ancient teeth to clarify what plant foods Easter Islanders ate before Europeans arrived.
Such calcified plaque was ''an excellent target'' for studying plants in an ancient diet, because plant microfossils - called phytoliths - became ''embedded in dental calculus'' throughout a person's life.
This could help show some plant foods people were eating, which was ''not an easy task'', she said.'.
Also called Rapa Nui, Easter Island was colonised about the 13th century and is famed for mysterious large stone statues or moai.
Ms Tromp and her former Idaho State University MSc supervisor, John Dudgeon, have just published research clearing up their previous puzzling finding that palm may have been a staple plant food for Easter Islanders, over several centuries.
The researchers had earlier found most phytoliths embedded in the plaque were from palm trees, but other evidence suggested palms actually became extinct after initial colonisation.
Their further analysis, newly published in the Journal of Archaeological Science, showed starch grains were identified in dental calculus removed from 30 teeth, from previously excavated burials.
Starch grains consistent with modern sweet potato were found in the dental plaque.
The researchers also tested modern sweet potato skins grown in sediment similar to that of Rapa Nui's and found their skins, during growth, seemed to incorporate phytoliths from the soil, she said.
The findings could affect research worldwide by showing that some microfossils found in plaque were not necessarily directly from the plants eaten by early inhabitants, but may have been taken up from the soil later by other plants.
