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This work deals with the specific studies of three main sources of uncertainty in electron spin resonance (ESR) dosimetry/dating of fossil tooth enamel: (1) the precision of the ESR measurements, (2) the long-term signal fading the selection of the fitting function. They show a different influence on the equivalent dose (D(E)) estimates. Repeated ESR measurements were performed on 17 different samples: results show a mean coefficient of variation of the ESR intensities of 1.20 ± 0.23 %, inducing a mean relative variability of 3.05 ± 2.29 % in the D(E) values. ESR signal fading over 5 y was also observed: its magnitude seems to be quite sample dependant but is nevertheless especially important for the most irradiated aliquots. This fading has an apparent random effect on the D(E) estimates. Finally, the authors provide new insights and recommendations about the fitting of ESR dose-response curves of fossil enamel with a double saturating exponential (DSE) function. The potential of a new variation of the DSE was also explored. Results of this study also show that the choice of the fitting function is of major importance, maybe more than the other sources previously mentioned, in order to get accurate final D(E) values.

The Banyoles mandible presents a puzzle. Its anatomy has been described as pre-Neandertal, but the travertine in which it was found has been dated to 45,000 +/- 4000 years. By this time, any pre-Neandertals had supposedly been absent from the European fossil record for more than 100,000 years. It was therefore proposed that the age of the travertine may represent a minimum age estimate, with the mandible possibly having been reworked from older deposits. We carried out a non-destructive ESR analysis of an enamel fragment removed from a molar and performed a series of in situ laser ablation U-series analyses on dentine fragments adjacent to the enamel piece. The analyses resulted in an apparent combined ESR-U-series age of 66,000 +/- 7000 years. The encasing travertine matrix was also analyzed for U-series isotopes and showed signs of U-mobilization. It cannot be excluded that the travertine matrix is older than the previously determined age. If the mandible was not reworked, then the combined ESR-U-series result on the tooth enamel would give its best age estimate. If, on the other hand, the mandible was reworked from another deposit, the actual ESR-U-series age will depend on the external dose rate from the previous matrix and the depth of its burial, which controls the degree of the attenuation of the cosmic dose rate over time. Considering a range of possible burial histories, the mean age of the mandible would lie somewhere between the combined ESR-U-series age and the previously determined age of the travertine matrix. Regarding the morphology of the mandible, a review of its features in the context of larger Neandertal samples indicates that the anatomy of the specimen is not incompatible with such a young age determination, although it further highlights morphological variation in the late Neandertal sample.

In order to resolve long-standing issues surrounding the age of the Skhul early modern humans, new analyses have been conducted, including the dating of four well-provenanced fossils by ESR and U-series. If the Skhul burials took place within a relatively short time span, then the best age estimate lies between 100 and 135 ka. This result agrees very well with TL ages obtained from burnt flint of 119+/-18 ka (Mercier et al., 1993). However, we cannot exclude the possibility that the material associated with the Skhul IX burial is older than those of Skhul II and Skhul V. These and other recent age estimates suggest that the three burial sites, Skhul, Qafzeh and Tabun are broadly contemporaneous, falling within the time range of 100 to 130 ka. The presence of early representatives of both early modern humans and Neanderthals in the Levant during Marine Isotope Stage 5 inevitably complicates attempts at segregating these populations by date or archaeological association. Nevertheless, it does appear that the oldest known symbolic burials are those of early modern humans at Skhul and Qafzeh. This supports the view that, despite the associated Middle Palaeolithic technology, elements of modern human behaviour were represented at Skhul and Qafzeh prior to 100 ka.

In view of a decade of progress in ESR dating we have revised the ESR chronology of Border Cave. A detailed gamma ray survey in 1994 and newly calculated beta attenuation data led to total dose rate estimations that are between 0 and 30% smaller than previously estimated. Accordingly, the resulting ESR age estimates are between 0 and 30% older. The ESR dates are now in good agreement with independent age estimates, particularly(14)C and amino acid racemization. New ESR dates for the lowermost dated sedimentary layer, 5 WA (white ash), indicate that the sedimentation of the sequence started around 200 ka ago., (Copyright 2001 Academic Press.)

In order to determine the components which give rise to the EPR spectrum around g = 2 we have applied Maximum Likelihood Common Factor Analysis (MLCFA) on the EPR spectra of enamel sample 1126 which has previously been analysed by continuous wave and pulsed EPR as well as EPR microscopy. MLCFA yielded agreeing results on three sets of X-band spectra and the following components were identified: an orthorhombic component attributed to CO2-, an axial component (CO3(3-)), as well as four isotropic components, three of which could be attributed to SO2-, a tumbling CO2- and a central line of a dimethyl radical. The X-band results were confirmed by analysis of Q-band spectra where three additional isotropic lines were found, however, these three components could not be attributed to known radicals. The orthorhombic component was used to establish dose response curves for the assessment of the past radiation dose, D(E). The results appear to be more reliable than those based on conventional peak-to-peak EPR intensity measurements or simple Gaussian deconvolution methods.

The archaeological and hominid site of Border Cave (KwaZulu, South Africa) has a stratigraphic sequence covering the Middle and Later Stone Ages (MSA and LSA). It has been proposed that four hominid specimens recovered there (BC1 and BC2 of uncertain provenance, and BC3 and BC5 recovered from MSA layers) represent very early examples of anatomically modern humans, supporting an early late-Pleistocene appearance of modern Homo sapiens in Africa. This early appearance, however, has been questioned, largely because of doubts about the stratigraphic positions associated with the specimens and because of the lack of a reliable chronology for the stratigraphic sequence. We now report on the first comprehensive radiometric dating analysis of Border Cave, using electron spin resonance (ESR) on teeth within sediment layers. BC3 is likely to be approximately 70-80 kyr old, and BC5, 50-65 kyr old. BC1 and BC2 are almost certainly less than 90 kyr old. These results, although younger than some age estimates, support the early occurrence of anatomically modern humans at Border Cave. In addition, our results suggest that the Howiesons Poort lithic industry (approximately 45-75 kyr) and the MSA-LSA transition (approximately 35 kyr) are younger than often believed.