It has become clear that there have been major problems with dating reliability and accuracy across the Paleolithic in general, with studies highlighting issues with underestimation of the ages of different dated samples from previously analyzed sites (6). At Mezmaiskaya, the AMS dates obtained for the Neanderthal excavated above the previously dated individual were substantially older (9). In both cases, revised radiocarbon dates produced with more robust chemical pretreatment methods have illustrated significant underestimates in the previous dates that cannot be reconciled with a hypothesis of late-surviving refugial Neanderthals. However, for Vi-207, the 30-k Da fraction obtained produced a C/N ratio of 4.3, which indicates the presence of a high molecular weight contaminant.We have been working on redating some of the purported late-surviving Neanderthal sites from around Europe, which have included human and archaeological remains from sites such as Mezmaiskaya (Russia), where a previous directly dated Neanderthal infant yielded a radiocarbon age of ∼29,000 B. (7), and Zafarraya (Spain), which was thought to contain Neanderthal remains clustering in age around a small group of U-series–dated animal bones between 33,400 and 28,900 B. This, along with other AMS dates from cut-marked fauna from the same archaeological horizons, suggested the original date of 29,000 B. The Neanderthal fossil remains from level G of Vindija Cave in northern Croatia have remained in the literature as potentially late individuals. (14) attempted to redate these specimens by taking the very small amounts of collagen remaining from the original sample pretreatment and ultrafiltering the product before AMS dating. The radiocarbon date for this sample could therefore include a higher molecular weight noncollagenous contaminant, possibly cross-linked to the collagen.Vi-207 is a right posterior mandible and Vi-208 is a parietal fragment, both showing Neanderthal-specific morphology (11, 12). This would imply a more extensive temporal overlap between Neanderthals and early modern humans in central Europe than has recently been documented (4).The initial radiocarbon results were 29,080 ± 400 B. In addition to the Neanderthal remains, level G has yielded a small archaeological assemblage that contains techno-typologically Middle and Upper Paleolithic lithic artifacts plus several distinctively early Upper Paleolithic osseous points (12).We decided to attempt to redate it, using a larger starting mass of bone powder.
This is an indicator of collagen preservation (20).Given the evidence from the Peștera cu Oase specimen, which demonstrates a recent Neanderthal ancestry in a 40,000 cal B. modern human from the Danube corridor (5), the renewed dating of the Vindija remains is overdue. On the basis of the potential problems associated with the small size of the redated samples and the potential for remaining contaminants, Ox A-X-2089-06 was considered to be a minimum age (14).Two specimens, Vi-207 and Vi-208, were originally directly AMS dated in the late 1990s at the Oxford Radiocarbon Accelerator Unit (ORAU). If the dates are even approximately correct, however, it makes them the most recent known Neanderthals.After the organism dies, carbon-14 continues to decay without being replaced.To measure the amount of radiocarbon left in a artifact, scientists burn a small piece to convert it into carbon dioxide gas.
Radiation counters are used to detect the electrons given off by decaying C-14 as it turns into nitrogen.