Abstract
The prehistory of the Mediterranean region has long been a subject of considerable interest, particularly the links between human groups and regions of origin. We utilize the spatial variation in the δ2H and δ18O values of precipitation (isoscapes) to develop proxies for geographic locations of fauna and humans. Bone collagen hydrogen isotope ratios (δ2H) in cattle (and to a lesser extent, ovicaprids) across the Mediterranean reflect the isotopic differences observed in rainfall (but δ18O values do not). We conclude that δ2H in herbivore bone collagen can be used as a geolocation tracer and for palaeoenvironmental studies such as tracing past isotopic variations in the global hydrological cycle. In contrast, human bone δ2H values are relatively tightly grouped and highly distinct from precipitation δ2H values, likely due to human-specific food practices and environmental modifications. Given the inter-species variability in δ2H, care should be taken in the species selected for study.
Highlights
Migration is a profoundly important part of human existence, from the dispersal of Homo sapiens out of Africa to the past and present movement of humans over the globe
The isotopic variation in precipitation can be incorporated into biological tissues and serve as a tracer of location, as exemplified by δ2H in bird feather keratin used for geo-location of the origin of migrant birds[10,11], δ2H and δ18O variation in human hair keratin with water variation[12], and δ18O in tooth enamel apatites used to distinguish non-local individuals[13]
We investigate whether bone collagen δ2H and δ18O values vary spatially, in concert with the longitudinal variation in precipitation δ2H, δ18O, and d excess values
Summary
Migration is a profoundly important part of human existence, from the dispersal of Homo sapiens out of Africa to the past and present movement of humans over the globe. Hydrogen and oxygen isotope ratio variations are products of the global hydrological cycle, influenced by temperature and atmospheric transport from source to precipitation location; as a result, δ2H and δ18O in precipitation can vary significantly with geography The distribution of these isotopes across the Mediterranean basin was first described by Gat and Carmi[7]. For applications to palaeoenvironmental and past migration questions, bone collagen offers advantages over other tissues: i) bones are often preserved in the geological and archaeological record (in contrast to keratin), allowing direct isotopic study of the individual of interest; ii) bone collagen reflects an integrated, albeit variable time period[20,21] in contrast to enamel apatite, which is formed at discrete ages and may not capture migration ‘events’; iii) collagen may be directly dated by radiocarbon. We investigate whether bone collagen δ2H and δ18O values vary spatially, in concert with the longitudinal variation in precipitation δ2H, δ18O, and d excess values
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