Authors:	Bourgon, Nicolas
Title:	Zinc Isotope Systematics in Terrestrial Food Webs: Implications for the Trophic Ecology of Tropical Hunter-Gatherer of Late Pleistocene Southeast Asia
Online publication date:	6-Apr-2022
Year of first publication:	2022
Language:	english
Abstract:	This thesis explores the use of “non-traditional” stable isotopes in archeology and paleontology, specifically isotopes of the trace element zinc (Zn) from tooth enamel to obtain dietary information from fossil specimens. Throughout this thesis, the use of zinc stable isotopes is explored through methodological and application perspectives, addressing some analytical challenges and developing study designs that are optimized for extracting robust dietary data from fossil materials. In particular, this method allows assessing the trophic level of a consumer, i.e., its relative dietary reliance on plant or animal resources. While nitrogen stable isotope (δ15N) analysis of bone or dentin collagen is an established method for trophic level assessment, such method is limited by protein preservation. Trophic level assessment of fossils beyond the Late Pleistocene, or coming from adverse taphonomic settings such as tropical and subtropical environments, are mostly unfeasible with this conventional method. However, the 66Zn/64Zn ratio (expressed as δ66Zn value) in bioapatite shows promise as a proxy to infer trophic and dietary information from fossil vertebrates, even under adverse taphonomic conditions. Indeed, zinc is incorporated as a trace element in the enamel bioapatite and thus has a better long-term preservation potential of diet-related isotope compositions than collagen-bound nitrogen. The first part of this thesis aims at giving an overview of zinc isotope analysis in paleodietary reconstructions, outlining principles of zinc isotope systematics and highlighting the potential and challenges of this analysis for archeology and paleontology. The lack of a strongly defined interpretative framework and comparative data are key obstacles to using zinc stable isotopes for paleodietary reconstructions. The second part of this thesis examines the preservation potential of pristine diet-related zinc isotope ratios under tropical conditions with poor collagen preservation, such as the studied depositional context in Southeast Asia. Analyses were conducted on the enamel of fossil teeth from the Late Pleistocene (38.4–13.5 ka) mammalian assemblage of Tam Hay Marklot (THM) cave in northeastern Laos, representing the first use of zinc isotopes on fossils for paleodietary studies. Distinct trophic discriminations according to expected feeding habits were obtained from enamel δ66Zn values of the fossil taxa. Moreover, trace element and zinc concentration profiles suggest an excellent long-term preservation potential of original zinc isotope compositions and validate the use of this method for paleodietary studies. The third part of this thesis comprises an assessment of zinc contamination from gloves used during sample preparation, using teeth of a population of early Holocene hunter-gatherers from Lapa do Santo, Brazil. No sign of significant zinc contamination was identified, and the primary source of zinc isotope variability in the Lapa do Santo population appeared associated with dietary transitions. For the first time, the potential of zinc stable isotope values as a proxy to trace age at weaning was demonstrated. The fourth part of this thesis involves the application of zinc isotope ratios to assess the reliance on plant or animal resources of a Late Pleistocene (63–46 ka) fossil Homo sapiens individual from Tam Pà Ling, one of the earliest-known anatomically modern humans in tropical Southeast Asia. The results highlighted a diet comprised of substantial amounts of plant and animal matter, which contrasts with most trophic level assessments of contemporaneous hunter-gatherer humans from other regions that comprise higher proportions of animal matter in their diet. It also reinforces a growing body of evidence for early human foragers’ occupation and adaptation to tropical rainforest environments. These results further illustrate the potential of the isotopic ratios of zinc in bioapatite to bypass the taphonomical limitations of collagen-bound nitrogen isotopes, allowing insights otherwise unobtainable.
DDC:	300 Sozialwissenschaften 300 Social sciences 540 Chemie 540 Chemistry and allied sciences 560 Paläontologie 560 Paleontology
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 09 Chemie, Pharmazie u. Geowissensch.
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-6832
URN:	urn:nbn:de:hebis:77-openscience-19b8b34a-1943-4761-b373-0b5b42acec513
Version:	Original work
Publication type:	Dissertation
License:	CC BY-ND
Information on rights of use:	https://creativecommons.org/licenses/by-nd/4.0/
Extent:	328 Seiten, Illustrationen, Diagramme
Appears in collections:	JGU-Publikationen