Figure 4. Labial scratches on Regourdou 19s anterior teeth. doi:10.1371/journal.pone.0043949.g004 three standardized sites (see Methods, Text S1) and three- dimensional cortical bone distribution were done. Variation in cortical area (CA), which relates to the resistance of the shaft to compressive/tensional axial loads, and polar second moment of area (J), reflecting the torsional and average bending rigidity [31], shows an ipslateral asymmetry for all four bones. The entire set of results supports a systematically higher biomechanical resistance to charges in compression/tension and, mostly, in torsion character- izing the right upper limb of this Neandertal individual. Interestingly, the microtomographic-based record shows that, despite the functional unity of the upper limb chain, its segments possess individually, at different degrees, asymmetry in strength loads (Figure 2). The clavicle recorded the highest level of asymmetry (mean difference in CA = 17.8%; J = 40.3%), closely followed by the ulna (16.2% and 38.5%, respectively); the radius for CA (8.4%) and the humerus for J (21%) are the least asymmetric shafts (see Table S1). Nonetheless, compared to the currently available Neandertal figures, which are mostly radio- Figure 5. Mosaic plot of scratch angles on all anterior teeth. Scratch intervals follow ref 7. doi:10.1371/journal.pone.0043949.g005 PLOS ONE | www.plosone.org 3 August 2012 | Volume 7 | Issue 8 | e43949 Right-Handed Neandertals graphically-based [32,33], the humerus displays only a relatively modest degree of right dominance (mean difference in CA = 11.7%; J = 21%). At the humeral midshaft, the Neandertal ranges of variation are 18.6–43.2% and 53.0–83.9% for CA and J, respectively, while their corresponding values in Regourdou 1 (measured at 44%, as the midshaft is lacking on the left humerus) correspond to 11% and 16.1%. Along with cross-sectional geometric properties, the same pattern of fluctuating bilateral asymmetry in Regourdou 1 is shown when cortical bone volume distribution is considered. In all but the humerus, asymmetry is expressed to a greater extent at the distal (lateral for the clavicle) portion of the shaft (25–45% of the biomechanical length for all but the humerus, where it corresponds to the 24–44% segment). For this portion, volumetric asymmetry ranges from 8.3% in the humerus (its proximal portion reaching 15.6%), up to 23.1% in the clavicle (see Tables S1 & S2). As a whole, while the extent of bilateral asymmetry displayed by its humerus was not as marked as recorded in other Neandertal individuals, this new body of data shows that Regourdou 1 was consistently larger on the right side for most of the external and endostructural measures. From the asymmetry in the upper limb bones, Regourdou 1 was right-handed. Results: The Mandibular Teeth Regourdou preserves a complete set of fully erupted, permanent teeth (Figure 3). All show little or moderate attrition, but occlusal wear on the incisors and canines is more marked than on the premolars and molars, a feature typical of Neandertals. Using Molnar’s scale the anterior teeth show wear stages 4–5, while premolar and molar wear ranges is less, ranging between 2–4 [34]. This differential wear is an indication that Neandertals used their anterior teeth as a ‘third hand’ in manipulating objects [35]. Often called the ‘stuff and cut’ technique [36], likely more than food was involved. Heavier occlusal wear on the anterior teeth is matched by marked scratching on the labial (lip) surfaces of the incisors and canines. Unaffected by this wear, the labial aspect of all teeth is well-preserved, without evidence of much post-depositional corrosion or abrasion. Figure 4 shows the heavily scratched labial surfaces of the six mandibular teeth of Regourdou 1. Striae are similarly distributed between the right (52.8%) and left (47.2%) sides, but not across the six teeth (Figures S1, S2 and S3). About 78% (297/382) of the scratches occur on the incisors with the remainder on the two canines. Together, the four incisors average 77.7 scratches and lateral incisors show nearly twice the number of scratches (mean = 98) compared to the central incisors (mean = 50). Striae are almost evenly distributed on the labial aspect of booth central