Dental size variation in the Atapuerca-SH Middle Pleistocene hominids.

The Middle Pleistocene Atapuerca-Sima de los Huesos (SH) site in Spain has yielded the largest sample of fossil hominids so far found from a single site and belonging to the same biological population. The SH dental sample includes a total of 452 permanent and deciduous teeth, representing a minimum of 27 individuals. We present a study of the dental size variation in these hominids, based on the analysis of the mandibular permanent dentition: lateral incisors, n=29; canines, n=27; third premolars, n=30; fourth premolars, n=34; first molars, n=38; second molars, n=38. We have obtained the buccolingual diameter and the crown area (measured on occlusal photographs) of these teeth, and used the bootstrap method to assess the amount of variation in the SH sample compared with the variation of a modern human sample from the Museu Antropologico of the Universidade of Coimbra (Portugal). The SH hominids have, in general terms, a dental size variation higher than that of the modern human sample. The analysis is especially conclusive for the canines. Furthermore, we have estimated the degree of sexual dimorphism of the SH sample by obtaining male and female dental subsamples by means of sexing the large sample of SH mandibular specimens. We obtained the index of sexual dimorphism (ISD=male mean/female mean) and the values were compared with those obtained from the sexed modern human sample from Coimbra, and with data found in the literature concerning several recent human populations. In all tooth classes the ISD of the SH hominids was higher than that of modern humans, but the differences were generally modest, except for the canines, thus suggesting that canine size sexual dimorphism in Homo heidelbergensis was probably greater than that of modern humans. Since the approach of sexing fossil specimens has some obvious limitations, these results should be assessed with caution. Additional data from SH and other European Middle Pleistocene sites would be necessary to test this hypothesis.

Bermúdez de Castro JM ，Sarmiento S ，Cunha E ，Rosas A ，Bastir M ... -  《journal of human evolution》

Dental remains from Atapuerca-TD6 (Gran Dolina site, Burgos, Spain).

A descriptive and comparative study of the human dental remains recovered from level six (Aurora stratum) of the Gran Dolina (TD) site, Sierra de Atapuerca, northern Spain, is presented. The TD6 dental sample consists of two deciduous and 28 permanent teeth, belonging to a minimum of six individuals. Paleomagnetic analyses of the TD sequence suggest an age for the Aurora stratum of greater than 780 ka. The associated fossil macro- and micrommals are consistent with a date for the Atapuerca-TD6 hominids at the end of the Early Pleistocene. As a whole, the size of the TD6 teeth is large and comparable to that of the African Lower Pleistocene hominids. Most morphological dental traits are plesiomorphic for the genus Homo, whereas the shape analysis has revealed some size-related trends that differ from those seen in early Homo. Thus, the relative size increase of the maxillary and mandibular anterior teeth and buccolingual diameter of the first molars, the reduction of the third molars and lower canines, and the P(3)>P(4)size sequence are all characteristic of the population represented by the TD6 hominids. The morphological evidence suggests that the TD6 hominids are closer to African Lower and early Middle Pleistocene hominids than they are to European Middle Pleistocene hominids. However, some dental traits of the TD6 hominids, such as the expansion of the anterior teeth, the P(3)>P(4)size sequence, and the morphology of the lower canine also suggest an evolutionary continuity between the population represented by these hominids and the European Middle Pleistocene population. Furthermore, dental evidence indicates that the TD6 hominids are clearly distinct from Asian H. erectus. Dental evidence also suggests that the TD6 hominids could represent an evolutionary connection between H. ergaster and H. heidelbergensis.

Bermúdez de Castro JM ，Rosas A ，Nicolás ME 《journal of human evolution》

Sexual dimorphism in the Atapuerca-SH hominids: the evidence from the mandibles.

The pattern of sexual dimorphism in 15 mandibles from the Atapuerca-SH Middle Pleistocene site, attributed to Homo heidelbergensis, is explored. Two modern human samples of known sex are used as a baseline for establishing sexing criteria. The mandible was divided for analysis into seven study regions and differential expression of sexual dimorphism in these regions is analysed. A total of 40 continuous and 32 discrete variables were scored on the mandibles. The means method given in Regh & Leigh (Am. J. phys. Anthrop.110, 95-104, 1999) was followed for evaluating the potential of correct sex attribution for each variable. On average, the mandibles from the Atapuerca-SH site present a degree of sexual dimorphism about eight points higher than in H. sapiens samples. However, mandibular anatomy of the European Middle Pleistocene hominid records sexual dimorphism differentially. Different areas of the Atapuerca-SH mandibles exhibit quite distinct degrees of sexual dimorphism. For instance, variables of the alveolar arcade present very low or practically no sexual dimorphism. Variables related to overall size of the mandible and symphysis region present a medium degree of sex differences. Finally, ramus height, and gonion and coronoid process present a high degree of sexual dimorphism (indexes of sexual dimorphism are all above 130%). Whether this marked sexual dimorphism in specific anatomical systems affects sexual differences in body size is not completely clear and further studies are needed. Sexual differences detected in the mandible of modern humans have at least two components: differences related to musculo-skeletal development and differences related to a different growth trajectory in males and females (relative development of some of the basal border features). The Atapuerca-SH mandibles display little variation in the basal border, however. The limited variation of this mandibular region may indicate that the pattern of sexual variation in H. heidelbergensis is different enough to that of H. sapiens to caution against simple extrapolation of criteria from one pattern to the other.

Rosas A ，Bastir M ，Martínez-Maza C ，Bermúdez de Castro JM ... -  《journal of human evolution》

Pattern of dental development in Hominid XVIII from the Middle Pleistocene Atapuerca-Sima de los Huesos site (Spain).

. We describe the pattern of dental development of Hominid XVIII from the Middle Pleistocene Sima de los Huesos (SH) site of the Sierra de Atapuerca (Burgos, Spain). As expected, this pattern is similar to that of modern humans. A delay of development of the lower and upper canines was observed. In contrast, the relative advanced development of the lower second molars and, especially, the upper and lower third molars is noteworthy. This latter feature seems to be common in Pleistocene hominids, and suggests that the pattern of dental development evolved in the genus Homo during the Pleistocene. In European Middle Pleistocene hominids, this pattern probably was facilitated by the extra space available in the mandible and maxilla for developing teeth.

Bermudez De Castro JM ，Rosas A 《AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY》

Enamel hypoplasia in the middle pleistocene hominids from Atapuerca (Spain).

Bermúdez de Castro JM ，Pérez PJ 《AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY》