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The Distribution and Biogenic Origins of Zinc in the Mineralised Tooth Tissues of Modern and Fossil Hominoids: Implications for Life History, Diet and Taphonomy.

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Zinc is incorporated into enamel, dentine and cementum during tooth growth. This work aimed to distinguish between the processes underlying Zn incorporation and Zn distribution. These include different mineralisation processes, the physiological events around birth, Zn ingestion with diet, exposure to the oral environment during life and diagenetic changes to fossil teeth post-mortem. Synchrotron X-ray Fluorescence (SXRF) was used to map zinc distribution across longitudinal polished ground sections of both deciduous and permanent modern human, great ape and fossil hominoid teeth. Higher resolution fluorescence intensity maps were used to image Zn in surface enamel, secondary dentine and cementum, and at the neonatal line (NNL) and enamel-dentine-junction (EDJ) in deciduous teeth. Secondary dentine was consistently Zn-rich, but the highest concentrations of Zn (range 197-1743 ppm) were found in cuspal, mid-lateral and cervical surface enamel and were similar in unerupted teeth never exposed to the oral environment. Zinc was identified at the NNL and EDJ in both modern and fossil deciduous teeth. In fossil specimens, diagenetic changes were identified in various trace element distributions but only demineralisation appeared to markedly alter Zn distribution. Zinc appears to be tenacious and stable in fossil tooth tissues, especially in enamel, over millions of years.


Peer reviewed: True

Acknowledgements: We thank the Government of Kenya and the National Museums of Kenya for the continued use and access to precious fossil material in their care. We thank Meave Leakey, Emma Mbua and Samuel Muteti for enabling aspects of this study. We extend our sincere thanks to Yoel Rak for making material from Amud, Israel, available to us for this study. We thank the curators of the Elliot Smith Collection at UCL, the Ditsong National Museum of Natural History, Pretoria, South Africa, the Duckworth Laboratory (University of Cambridge, UK), Holly Smith and Salvador Moyà-Solà for making specimens available to us. We are grateful to Anastasia Brozou, Gerald Falkenberg and those at DESY who have developed techniques employed in this study, as well as the DESY User Office. This research was supported in part through the Maxwell computational resources operated at Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany. This research benefited from the scientific framework of the University of Bordeaux’s IdEx “Investments for the Future” program/GPR “Human Past”. We thank the editors and four anonymous reviewers for their helpful comments.

Publication status: Published

Funder: Calleva Foundation within the Centre for Human Evolution Research (CHER) at the Natural History Museum, London

Funder: Max Planck Society, Germany

Funder: French Centre National de la Recherche Scientifique (CNRS) at the Université de Bordeaux


SXRF, enamel, enamel thickness, mineralisation process, neonatal line, trace elements

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Biology (Basel)

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Deutsches Elektronen-Synchrotron, (DESY) Hamburg, (a member of the Helmholtz Association HGF) on the PETRA III P06 beamline (I-20160686, I-20180047, I-20190203, I-20210133)