Forensic research on the year of birth by human teeth sequential sampling in the range of 14C peak
Miss YiHsien Lin1, Prof. Xiaohong Wu1
1School Of Archaeology And Muselogy, Peking University, Beijing, China
The sequential dentine samples is a potentially powerful method for studying the early life histories of individuals. Enamel and dentine grow incrementally, and the isotopic composition of the tissues on different time scales (daily to yearly) remains in the tooth. Except for the wisdom teeth (the third molars), the permanent dentition of humans are fully developed when they are about 12 years old. Therefore, the teeth completely record the period of rapid growth in the early life of humans. However, the incremental growth structure of dentine is full of complexity. Current methods, such as horizontal cross-section sampling of half or quarter of a tooth from which inorganic minerals have been removed, have the risk of mixing multiple growth layers or containing unwanted cementum or secondary dentine. These methods also need to destroy most of the teeth. A new method with low destructiveness and relatively simple experimental procedures was published recently, which can reduce sample loss, increase resolution in time series, and improve the accuracy of age-alignment between different individuals. This new experimental protocol allowed us to perform sequential sampling of small samples (cylindrical samples with a diameter of 1 mm) on 2 mm wide longitudinal slices of teeth, as well as inferring the corresponding developmental age of the sequential samples from the average growth rate of dentine. The teeth from 5 individuals with known ages were collected. Small samples were taken in sequence of dentine based on the difference in the growth rate of different anatomical parts of the tooth. The dentine collagen were graphitized and the measurements of radiocarbon dating were performed on compact accelerator mass spectrometry at PKU. Radiocarbon dating results of the dentine sequential samples from the first molar tooth gave more accurate age within 1-2 years difference, comparing with the known birth year of one dividual. The radiocarbon dating results from the second premolar teeth were not matched with the known ages of the individuals. The differences between the age of measurement and known age are about 1-20 years. It can be concluded that the radiocarbon dating of the first molar or the second molar with the sequential sampling can be applied to study the birth year of human individuals in order to solve the forensic questions.
Xiaohong Wu, Professor in archaeological sciences at School of Archaeology and Museology, Peking University.