How studying teeth can reveal insights about prehistoric life

Human enamel is the mineralised surface that forms the tooth crown. Enamel, unlike bone, does not remodel.

Remains were mixed. To avoid sampling the same individual twice, only the right or left mandibular first molar was sampled. The study analysed oxygen, strontium and carbon isotope values in molars from the Umm An Nar and Wadi Suq period tombs from the Shimal necropolis, Ras Al Khaimah.

Oxygen isotope values are determined by water drank in early life, as the enamel grows and develops. These oxygen values change in response to climate change.

The first molar mineralisation of the crown is usually complete by age four and a half. The study found higher oxygen isotope values in the Wadi Suq period. This likely indicates local water sources changed with growing aridity, an expected shift.

Strontium isotope values in human dental enamel can indicate where people lived in childhood, which can be compared to burial sites to measure mobility. Strontium is a soft metal of the alkaline earth series. Different geographies have different strontium isotope values that vary according to the type and age of the bedrock.

The study found tight clustering of strontium values, suggesting a relatively sedentary lifestyle, at least in childhood. Mobility was therefore not as significantly a part of the lifestyle at this time as previously suggested.

If migration had occurred, it would have likely been between coast and mountains with distinctly different bedrocks and, therefore, strontium values. This is not the case in Shimal.

It is possible that certain groups or ages did not become mobile until later life, after their teeth enamel had formed.

Carbon isotopes values indicate diet. Stable carbon isotope data after the beginning of the Wadi Suq period, around 2000 BC, suggest a reliance on C3-based terrestrial plants or plant-consuming animals and not marine life, as formerly assumed. This indicates a relatively stable food source at Shimal during the transition. C3-based plants include wheat, barley, date palm and most fruits and vegetables.

Professor Gregoricka's previous research from 2013 found that diet became more restricted during the Umm An Nar to Wadi Suq transition period, but there was not the expected shift to a more marine-based diet, as had been believed based on shell middens.