New methodology to reconstruct in 2-D the cuspal enamel of modern human lower molars.

OBJECTIVES: In the last years different methodologies have been developed to reconstruct worn teeth. In this article, we propose a new 2-D methodology to reconstruct the worn enamel of lower molars. Our main goals are to reconstruct molars with a high level of accuracy when measuring relevant histological variables and to validate the methodology calculating the errors associated with the measurements. METHODS: This methodology is based on polynomial regression equations, and has been validated using two different dental variables: cuspal enamel thickness and crown height of the protoconid. In order to perform the validation process, simulated worn modern human molars were employed. The associated errors of the measurements were also estimated applying methodologies previously proposed by other authors. RESULTS: The mean percentage error estimated in reconstructed molars for these two variables in comparison with their own real values is -2.17% for the cuspal enamel thickness of the protoconid and -3.18% for the crown height of the protoconid. This error significantly improves the results of other methodologies, both in the interobserver error and in the accuracy of the measurements. CONCLUSIONS: The new methodology based on polynomial regressions can be confidently applied to the reconstruction of cuspal enamel of lower molars, as it improves the accuracy of the measurements and reduces the interobserver error. The present study shows that it is important to validate all methodologies in order to know the associated errors. This new methodology can be easily exportable to other modern human populations, the human fossil record and forensic sciences.

Fossil hominin radii from the Sima de los Huesos Middle Pleistocene site (Sierra de Atapuerca, Spain).

Complete radii in the fossil record preceding recent humans and Neandertals are very scarce. Here we introduce the radial remains recovered from the Sima de los Huesos (SH) site in the Sierra de Atapuerca between 1976 and 2011 and which have been dated in excess of 430 ky (thousands of years) ago. The sample comprises 89 specimens, 49 of which are attributed to adults representing a minimum of seven individuals. All elements are described anatomically and metrically, and compared with other fossil hominins and recent humans in order to examine the phylogenetic polarity of certain radial features. Radial remains from SH have some traits that differentiate them from those of recent humans and make them more similar to Neandertals, including strongly curved shafts, anteroposterior expanded radial heads and both absolutely and relatively long necks. In contrast, the SH sample differs from Neandertals in showing a high overall gracility as well as a high frequency (80%) of an anteriorly oriented radial tuberosity. Thus, like the cranial and dental remains from the SH site, characteristic Neandertal radial morphology is not present fully in the SH radii. We also analyzed the cross-sectional properties of the SH radial sample at two different levels: mid-shaft and at the midpoint of the neck length. When standardized by shaft length, no difference in the mid-shaft cross-sectional properties were found between the SH hominins, Neandertals and recent humans. Nevertheless, due to their long neck length, the SH hominins show a higher lever efficiency than either Neandertals or recent humans. Functionally, the SH radial morphology is consistent with more efficient pronation-supination and flexion-extension movements. The particular trait composition in the SH sample and Neandertals resembles more closely morphology evident in recent human males.

The Neandertals of northeastern Iberia: new remains from the Cova del Gegant (Sitges, Barcelona).

The present study describes a new juvenile hominin mandible and teeth and a new juvenile humerus from level V of the GP2 gallery of Cova del Gegant (Spain). The mandible (Gegant-5) preserves a portion of the right mandibular corpus from the M1 distally to the socket for the dc mesially, and the age at death is estimated as 4.5-5.0 years. Gegant-5 shows a single mental foramen located under the dm1/dm2 interdental septum, a relatively posterior placement compared with recent hominins of a similar developmental age. The mental foramen in Gegant-5 is also placed within the lower half of the mandibular corpus, as in the previously described late adolescent/adult mandible (Gegant-1) from this same Middle Paleolithic site. The Gegant-5 canine shows pronounced marginal ridges, a distal accessory ridge, and a pronounced distolingual tubercle. The P3 shows a lingually-displaced protoconid cusp tip and a distal accessory ridge. The P4 shows a slightly asymmetrical crown outline, a continuous transverse crest, a mesially placed metaconid cusp tip, a slight distal accessory ridge, and an accessory lingual cusp. The M1 shows a Y5 pattern of cusp contact and a well-developed and deep anterior fovea bounded posteriorly by a continuous midtrigonid crest. Gegant-4 is the distal portion of a left humerus from a juvenile estimated to be between 5 and 7 years old at death. The specimen shows thick cortical bone. Although fragmentary, the constellation of morphological and metric features indicates Neandertal affinities for these specimens. Their spatial proximity at the site and similar ages at death suggest these remains may represent a single individual. The addition of these new specimens brings the total number of Neandertal remains from the Cova del Gegant to five, and this site documents the clearest evidence for Neandertal fossils associated with Middle Paleolithic stone tools in this region of the Iberian Peninsula.

A symbolic Neanderthal accumulation of large herbivore crania.

This work examines the possible behaviour of Neanderthal groups at the Cueva Des-Cubierta (central Spain) via the analysis of the latter's archaeological assemblage. Alongside evidence of Mousterian lithic industry, Level 3 of the cave infill was found to contain an assemblage of mammalian bone remains dominated by the crania of large ungulates, some associated with small hearths. The scarcity of post-cranial elements, teeth, mandibles and maxillae, along with evidence of anthropogenic modification of the crania (cut and percussion marks), indicates that the carcasses of the corresponding animals were initially processed outside the cave, and the crania were later brought inside. A second round of processing then took place, possibly related to the removal of the brain. The continued presence of crania throughout Level 3 indicates that this behaviour was recurrent during this level's formation. This behaviour seems to have no subsistence-related purpose but to be more symbolic in its intent.

Early Pleistocene human humeri from the Gran Dolina-TD6 site (Sierra de Atapuerca, Spain).

In this report, we present a morphometric comparative study of two Early Pleistocene humeri recovered from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. ATD6-121 belongs to a child between 4 and 6 years old, whereas ATD6-148 corresponds to an adult. ATD6-148 exhibits the typical pattern of the genus Homo, but it also shows a large olecranon fossa and very thin medial and lateral pillars (also present in ATD6-121), sharing these features with European Middle Pleistocene hominins, Neandertals, and the Bodo Middle Pleistocene humerus. The morphology of the distal epiphysis, together with a few dental traits, suggests a phylogenetic relationship between the TD6 hominins and the Neandertal lineage. Given the older geochronological age of these hominins (ca. 900 ka), which is far from the age estimated by palaeogenetic studies for the population divergence of modern humans and Neandertals (ca. 400 ka), we suggest that this suite of derived "Neandertal" features appeared early in the evolution of the genus Homo. Thus, these features are not "Neandertal" apomorphies but traits which appeared in an ancestral and polymorphic population during the Early Pleistocene.