Quantifying the impact of µCT‐scanning of human fossil teeth on ESR age results

Abstract

Fossil human teeth are nowadays systematically CT-scanned by palaeoanthropologists prior to any further analysis. It has been recently demonstrated that this noninvasive technique has, in most cases, virtually no influence on ancient DNA preservation. However, it may have nevertheless an impact on other techniques, like Electron Spin Resonance (ESR) dating, by artificially ageing the apparent age of the sample. To evaluate this impact, we µCT-scanned several modern enamel fragments following the standard analytical procedures employed by the Dental Anthropology Group at CENIEH, Spain, and then performed ESR dose reconstruction for each of them. The results of our experiment demonstrate that the systematic high-resolution µCT-scanning of fossil hominin remains introduces a nonnegligible X-ray dose into the tooth enamel, equivalent to 15-30 Gy depending on the parameters used. This dose may be multiplied by a factor of ∼8 if no metallic filter is used. However, this dose estimate cannot be universally extrapolated to any µCT-scan experiment but has instead to be specifically assessed for each device and set of parameters employed. The impact on the ESR age results is directly dependent on the magnitude of the geological dose measured in fossil enamel but could potentially lead to an age overestimation up to 40% in case of Late Pleistocene samples, if not taken into consideration.

Combined US-ESR dating of fossil teeth from El Harhoura 2 cave (Morocco): New data about the end of the MSA in Temara region

“…An example of ESR spectrum is displayed in Fig.2 SM. This spectrum shows a non-horizontal baseline which may potentially impact the D e (Duval and Martín-Francés, 2017). This was evaluated on one sample (EH2-2730) by performing a baseline correction (using a cubic function) for each aliquot measured.…”

Response to Comment on “The earliest modern humans outside Africa”

“…Misliya-1 was CT-scanned three times prior to the ESR dating analysis (1). The x-ray dose during CT scanning is highly variable (6)(7)(8). On the basis of our recent study (7), we could roughly estimate that the total x-ray dose was approximately 30 Gy, resulting in an effective equivalent dose (D E ) value of 98.3 ± 5.3 Gy.…”

Enhancing the learning of evolutionary anthropology skills by combining student‐active teaching with actual and virtual immersion of Master's students in fieldwork, laboratory practice, and dissemination

“…Students are provided with the links to these platforms and are encouraged to visit them. They also receive information on the potential impact of X‐ray and synchrotron radiation on ancient DNA and ESR dating results, as well as guidelines for avoiding or limiting them (Duval & Martín‐Francés, 2017 ; Immel et al, 2016 ). The archives on the educational platform of the University of Bordeaux include 3D models specific to our field and laboratory research, intended for use as teaching resources associated with online exercises.…”