Paleobiology of El Sidrón sample shares, in several aspects, the common pattern for Neandertal populations: high incidence of dental hypoplasia and interproximal grooves, although no serious traumatic lesions are present (19). There are no "toothpick" grooves (20–22) so far in the El Sidrón dental sample. Adult 4 shows an elongated nonmasticatory wear in the mesial side of left lower canine, denoting the use of the mouth in activities other than mastication.
Dental Hypoplasia. Neandertals have been noted to have high levels of developmental stress indicators, especially dental enamel hypoplasias, indicating growth arrest periods (23–26). All of the individuals from El Sidrón present dental hypoplasia. Defects are well marked on the incisors (59%), canines (50%), premolars (58%), and molars (32%). Five individuals present two events of arrest, whereas Adult 3 shows up to four. Adolescent 2 presents an exceptionally severe episode of physiological stress. The highest frequency of hypoplasia is found to occur near the 4th year of life. Besides, four individuals also present dental hypoplasia near the 12th year of life. These data suggest weaning and adolescence as the life-history events more prone to nutritional stress (23) in the El Sidrón sample as well as significant survival of such events.
Paleopathology. Dental calculus is present, at variable degrees, in the adults and the adolescents. Mandible 2 shows alveolar bone resorption and an apical abscess (Fig. 2), consistent with a chronic apical peridontitis associated with traumatic occlusion (27). This sort of lesion is common among Neandertal lineage populations (28).
Interproximal Tooth Wear. Tooth-to-tooth contact occasionally shows a number of subvertical grooves, frequently found in Neandertal teeth (29, 30) and occasionally in other humans (31, 32). El Sidrón adults and adolescents all show interproximal grooves in 11 incisors, 5 canines, 17 premolars and 19 molars, ranging from 1 to 8 grooves per tooth (Fig. 3). The proximate causes of subvertical grooves have been controversial (29, 32), but it is generally accepted that they derive from high levels of masticatory stress, congruent with other aspects of Neandertal dental apparatus: beveling, labial wear striae, and nonocclusal wear (29, 33), attributes also observable in the El Sidrón sample.
Human-Induced Bone Modification. Unequivocal evidence of human-induced modification of human bones is observed in the Neandertals from El Sidrón. Methodology and quantification follow the criteria in ref. 34. Anthropic activity is evinced by the presence of cut marks, flakes, percussion pitting, conchoidal scars, and adhering flakes. Immature skull bones (frontal, temporal, and parietal) show a higher frequency of cut marks, possibly indicating skinning activities. Long bones (humerus, ulna, radius, and tibia) show short and deep cut marks related to disarticulation processes.
In contrast to other sites (35, 36), individuals seem to have been treated differentially. For instance, Mandible 3 shows clear cut marks on the ramus basal border (Fig. 3), whereas the others do not display any evidence of defleshing. It is generally accepted that the inference of cannibalism must be supported by a similarity of the modifications on the human remains to modifications of nonhuman remains (35, 36). The scarcity of faunal remains in the El Sidrón sample prevents a direct comparison with human bones. Yet, the clear evidence of bone breaking (conchoidal percussion scars) is presumably related to processing for marrow and brains, which strongly suggest a nutritional exploitation. Given the high level of developmental stress in the sample, some level of survival cannibalism would be reasonable.