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Human influence on ecological niches can drive rapid changes in the diet, behaviour and evolutionary trajectories of small mammals. Archaeological evidence from the Late Neolithic Loess Plateau of northern China suggests that the expansion of millet cultivation created new selective pressures, attracting small mammals to fields and settlements. Here, the authors present direct evidence for commensal behaviour in desert hares (Lepus capensis), dating to c. 4900 years ago. Stable isotope ratio analysis of hare bones from the Neolithic site at Yangjiesha shows a diachronic increase in a C4 (millet-based) diet, revealing, for the first time, the expansion of ancient human-hare interactions beyond the predator-prey relationship.
As part of the ongoing effort to improve the Northern Hemisphere radiocarbon (14C) calibration curve, this study investigates the period of 856 BC to 626 BC (2805–2575 yr BP) with a total of 403 single-year 14C measurements. In this age range, IntCal13 was constructed largely from German and Irish oak as well as Californian bristlecone pine 14C dates, with most samples measured with a 10-yr resolution. The new data presented here is the first atmospheric 14C single-year record of the older end of the Hallstatt plateau based on an absolutely dated tree-ring chronology. The data helped reveal a major solar proton event (SPE) which caused a spike in the production rate of cosmogenic radionuclides around 2610/2609 BP. This production event is thought to have reached a magnitude similar to the 774/775 AD production event but has remained undetected due to averaging effects in the decadal calibration data. The record leading up to the 2610/2609 BP event reveals a 11-yr solar cycle with varying cyclicity. Features of the new data and the benefits of higher resolution calibration are discussed.
A primary concern with dating skeletal material from oceanic environments is the effect of marine-derived carbon on resulting radiocarbon ages. Due to uncertainties in local marine reservoir effects and the proportion of marine carbon incorporated in bone, dates from archaeological skeletal material exhibiting marine dietary signatures have previously been characterized as problematic and removed from further analysis. While in certain instances this may be appropriate, in others it is not. This article presents 26 new 14C dates obtained from human teeth (dentin collagen) on Rapa Nui. The effect of the local marine reservoir on 14C ages is evaluated assuming a range of incorporated marine-derived carbon. The results indicate that the Rapa Nui 14C ages are not significantly different under varying realistic extreme ranges in estimates of the proportion of marine carbon consumed. The article argues that this is primarily due to the small local marine reservoir effect measured in Rapa Nui and relatively lower reliance on marine resources in the prehistoric and protohistoric population.
In forensic sciences, radiocarbon found in modern human nails and hair is evaluated to determine the year of death. However, 14C analyses presented herein of fingernails and hair from the same infant demonstrated 14C values of hair that were lower than would be expected (e.g. depleted relative to the fingernails by at least 10‰). These results prompted a series of 14C measurements on infant hair strands, fingernails, and infant shampoo, which suggested the presence of C contamination due to cosmetic products. To further evaluate these discrepancies, several hair strands and fingernail samples from multiple donors were collected, pretreated by several approaches, and measured using isotopic analysis (δ13C, δ15N, and C/N as well as 14C accelerator mass spectrometry). SEM images of the surface of chemically pretreated hair strands were also taken to inspect the performance of the chemical pretreatments applied. Our 14C and stable isotope results show that modern human hair is likely contaminated with fossil-fuel-derived carbon, which is found in most hair care products. Currently, the various chemical pretreatments available in the literature and presented herein show that it is not possible to completely remove foreign carbon contaminates. Thus, the human 14C and δ13C values between keratinous tissues (fingernails and hair) arc not in agreement. From these observations, it becomes apparent that isotopic interpretations using human hair should be used with extreme caution and additional work is needed for its use in forensic and dietary research.
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