A new collection of 49,000 year old Neandertal fossil humeri from the El Sidrón cave site (Asturias, Spain) is presented. A total of 49 humeral remains were recovered, representing 10 left and 8 right humeri from adults, adolescents, and a juvenile (not included in the analyses). 3D geometric morphometric (GM) methods as well as classic anthropological variables were employed to conduct a broad comparative analysis by means of mean centroid size and shape comparisons, principal components analysis, and cluster studies. Due to the fragmentary nature of the fossils, comparisons were organized in independent analyses according to different humeral portions: distal epiphysis, diaphysis, proximal epiphysis, and the complete humerus. From a multivariate viewpoint, 3D-GM analyses revealed major differences among taxonomic groups, supporting the value of the humerus in systematic classification. Notably, the Australopithecus anamensis (KP-271) and Homo ergaster Nariokotome (KNM-WT 15000) distal humerus consistently clusters close to those of modern humans, which may imply a primitive condition for Homo sapiens morphology. Australopithecus specimens show a high degree of dispersion in the morphospace. The El Sidrón sample perfectly fits into the classic Neandertal pattern, previously described as having a relatively wide olecranon fossa, as well as thin lateral and medial distodorsal pillars. These characteristics were also typical of the Sima de los Huesos (Atapuerca) sample, African mid-Pleistocene Bodo specimen, and Lower Pleistocene TD6-Atapuerca remains and may be considered as a derived state. Finally, we hypothesize that most of the features thought to be different between Neandertals and modern humans might be associated with structural differences in the pectoral girdle and shoulder joint.

duos. Los resultados genéticos, ratificados por datos osteológicos, definen a los neandertales de El Sidrón como un grupo homogéneo, con estrechos lazos familiares entre sus individuos. Finalmente, las numerosas evidencias del tratamiento antrópico de los restos hacen de El Sidrón un ejemplo paradigmático de prácticas de canibalismo entre los neandertales.Palabras clave: neandertal; fósil; paleoantropología; karst; canibalismo; ADN antiguo. AbstractThe archaeological project in the Gallery of the Osario of the cave of El Sidrón (Asturias, Spain) has recently concluded after 13 field seasons of detailed, methodical excavation. We present here a summary of the lines of research and the paleoanthropological studies carried out to date, as well as a brief perspective of the ongoing investigations. More than 2550 neandertal fossil remains have been recovered from this singular deposit, together with 400 pieces of Mousterian lithic industry, and less than 60 non-human remains. Sedimentological, taphonomic and structural analyses of the karst clarify that this fossil assemblage is in a secondary position and comes by mudflow from a gallery/shelter located in a superior level of the karst. All the skeletal parts are represented, and 13 individuals have been identified: 7 adults (3 males, 4 females), 3 adolescents (2 males, 1 female), 2 male juveniles and an infant. The El Sidrón collection constitutes the most numerous and diverse neandertal sample of the Iberian Peninsula, allowing systemic studies on tempo and modo of appearance of the derived characters in the neandertal lineage. The wide undertaken paleobiological research program includes the study of the different levels of biological organization, from demographic and evolutionary dynamics to molecular aspects. With regard to the latter, the extraction of DNA sequences has played a central role, with the characterization of the mt-DNA haplotype of 12 individuals, and with the inclusion of samples from El Sidrón in the Neandertal Genome and Exome projects. Results from the genetic and osteological studies define El Sidrón neandertals as a homogenous group, with narrow kinship bonds between their individuals. Finally, the numerous evidences of human-induced treatment of the bones make of El Sidrón a paradigmatic example of practices of cannibalism between the neandertals.

Approximately 90% of anatomically modern humans (AMHs) are right-handed. This handedness is related to laterality patterns of the upper limb due to habitual activity patterns which are known to leave marks on the bone structure. Various studies have shown that Neanderthals were also right-handed in very similar proportions to AMHs. Here, for the first time, 3D geometric morphometric techniques are used to study humeral laterality in a Spanish modern human population and to make a comparative study with a Neanderthal sample. Results obtained in the modern human population show a larger right humerus and clear differences in shape laterality. Shape differences in both epiphyses and in the complete humerus could be caused by non-allometric factors. This could suggest different activity pattern in both arms during life. Shaft shape laterality could be explained by allometric factors, i.e. shape variability is related to size variability. Neanderthals show a larger right humerus compared to the left and the mean shape comparison with the common anatomical regions presents a non-significant result. Finally, olecranon fossa width is the only feature that clearly differs between modern humans and Neanderthals, with geometric morphometric and linear measures being wider on the Neanderthal left side and wider on the modern human population right side. This difference may be due to a combination of different factors and behaviors that involve complete extension of the elbow joint.

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