The potential of dental calculus as a novel source of biological isotopic data

Stable isotope analysis has become an essential tool in investigations of ancient migration and paleodietary reconstruction. Because the biogeochemistry of bone collagen and apatite is well known, current methods rely almost exclusively on analyses of bones and teeth; however, dental calculus represents a potentially additional biological source of isotopic data from ancient skeletons. Dental calculus is a mineralized bacterial biofilm that forms on the surfaces of teeth. Sampling dental calculus does not damage the dentition and thus can be used in cases where it is not possible to perform destructive analyses of conventional mineralized tissues. Like bone and dentine, dental calculus contains both inorganic and organic components, allowing measurement of C, N, O, H, and Sr isotopes. Additionally, dental calculus forms as serial, non-remodeling laminar accretions on the tooth surface, opening up the possibility of analyzing discrete time points during the lifetime of an individual. However, as a microbial biofilm and not a human tissue, the biochemistry of dental calculus is complex, containing multiple calcium phosphate mineral phases, organic and inorganic food remains, hundreds of human and bacterial proteins, and diverse biomolecules from thousands of endogenous bacterial taxa. Isotopic investigation of dental calculus is still in its infancy, and many questions remain regarding its formation and processes of diagenesis. This chapter (1) reviews the unique advantages presented by dental calculus as a novel source of biological isotopic data, (2) critically evaluates published isotopic studies of dental calculus, and (3) explores the current challenges of dental calculus stable isotope analysis through a case study of an Ancient Puebloan Basketmaker II population from the American Southwest.Bioarchaeolog

Longitudinal profiles of rivers with a composite cross-section

In one-dimensional river modelling it is common to schematise the cross-section into a rectangular cross-section with a constant width. If a quasi-steady flow is assumed, the equilibrium longitudinal profile is known and unique: the bottom slope is constant and equals the water surface slope. However, numerical calculations at DELFT HYDRAULICS suggest that for rivers with a composite cross-section more equilibrium longitudinal profiles can exist. In addition, it appears that a stable curved equilibrium can exist. As an example, a river with floodplains can be mentioned to have a composite crosssection. This report contains a study on the equilibrium longitudinal profiles of rivers with a composite cross-section. In order to calculate these profiles, and their stability, three different models are applied to a schematised river. Calculations are done both analytically and numerically, and all results are visualized in phase diagrams.Hydraulic EngineeringCivil Engineering and Geoscience

Stable isotope chemistry reveals plantdominant diet among early foragers on the Andean Altiplano, 9.0-6.5 cal. ka

Current models of early human subsistence economies suggest a focus on large mammal hunting. To evaluate this hypothesis, we examine human bone stable isotope chemistry of 24 individuals from the early Holocene sites of Wilamaya Patjxa (9.0-8.7 cal. ka) and Soro Mik'aya Patjxa (8.0-6.5 cal. ka) located at 3800 meters above sea level on the Andean Altiplano, Peru. Contrary to expectation, Bayesian mixing models based on the isotope chemistry reveal that plants dominated the diet, comprising 70-95% of the average diet. Paleoethnobotanical data further show that tubers may have been the most prominent subsistence resource. These findings update our understanding of earliest forager economies and the pathway to agricultural economies in the Andean highlands. The findings furthermore suggest that the initial subsistence economies of early human populations adapting to new landscapes may have been more plant oriented than current models suggest. © 2024 Chen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]