Incremental distribution of strontium and zinc in great ape and fossil hominin cementum using synchrotron X-ray fluorescence mapping

Abstract

<jats:p>Cementum and the incremental markings it contains have been widely studied as a means of ageing animals and retrieving information about diet and nutrition. The distribution of trace elements in great ape and fossil hominin cementum has not been studied previously. Synchrotron X-ray fluorescence (SXRF) enables rapid scanning of large tissue areas with high resolution of elemental distributions. First, we used SXRF to map calcium, phosphorus, strontium and zinc distributions in great ape dentine and cementum. At higher resolution, we compared zinc and strontium distributions in cellular and acellular cementum in regions where clear incremental markings were expressed. We then mapped trace element distributions in fossil hominin dentine and cementum from the 1.55–1.65 million year old site of Koobi Fora, Kenya. Zinc, in particular, is a precise marker of cementum increments in great apes, and is retained in fossil hominin cementum, but does not correspond well with the more diffuse fluctuations observed in strontium distribution. Cementum is unusual among mineralized tissues in retaining so much zinc. This is known to reduce the acid solubility of hydroxyapatite and so may confer resistance to resorption by osteoclasts in the dynamic remodelling environment of the periodontal ligament and alveolar bone.</jats:p>

Zinc isotopes in Late Pleistocene fossil teeth from a Southeast Asian cave setting preserve paleodietary information

“…1 and SI Appendix, Figs. S12-S29) (19,(62)(63)(64) and, thus, lends further support to the preservation of a biogenic pattern. Furthermore, this outer Znrich layer is routinely removed mechanically during the enamel cleaning process for stable isotope analysis.…”

“…2 and SI Appendix, Figs. S18-S20 and S27-S30) (19,(62)(63)(64). The higher concentration in Zn in the first few tenths of microns of the outermost enamel layer is believed to be a biochemical signal that could be associated with the termination of the enamel maturation (63).…”

“…Of these, only one enamel cross-section segment showed Zn concentration distribution that did not follow the characteristic pattern observed for modern enamel (n = 10) of higher concentration in the outermost layer that decreases toward a constant level inwards (SI Appendix, Fig. S30) (19,(62)(63)(64). While the distribution of this one segment may indicate some postmortem alteration, none of the other three enamel cross-section segments analyzed from that same specimen (Panthera pardus, 34505) displayed an atypical pattern.…”

“…Among these, Zn isotope ratios ( 66 Zn/ 64 Zn, expressed as δ 66 Zn value) constitute a promising dietary indicator (11,14,(16)(17)(18). Indeed, Zn is incorporated as trace element in the enamel bioapatite and, thus, has a better long-term preservation potential compared to collagen-bound nitrogen, showing promise for dietary reconstructions in archeology and paleontology (19). It was not until 2012 that Van Heghe et al (20) began investigating the causes of the variability of δ 66 Zn values in a pilot study.…”

Parturitions, menopause and other physiological stressors are recorded in dental cementum microstructure

“…1), which is secreted and mineralized in incremental layers. As recently reviewed in Dean et al 22 cementum is part of the periodontium, which functions to attach and protect the tooth within the bony dental alveolus 23 . Collagen fiber bundles, extending between the alveolar bone and the root surface, form the periodontal ligament (PDL).…”