New interpretation of the Gran Dolina-TD6 bearing Homo antecessor deposits through sedimentological analysis.

Gran Dolina is a cavity infilled by at least 25 m of Pleistocene sediments. This sequence contains the TD6 stratigraphic unit, whose records include around 170 hominin bones that have allowed the definition of a new species, Homo antecessor. This fossil accumulation was studied as a single assemblage and interpreted as a succession of several human home bases. We propose a complete stratigraphic context and sedimentological interpretation for TD6, analyzing the relationships between the sedimentary facies, the clasts and archaeo-palaeontological remains. The TD6 unit has been divided into three sub-units and 13 layers. Nine sedimentary facies have been defined. Hominin remains appear related to three different sedimentary facies: debris flow facies, channel facies and floodplain facies. They show three kinds of distribution: first a group of scattered fossils, then a group with layers of fossils in fluvial facies, and third a group with a layer of fossils in mixed fluvial and gravity flow facies. The results of this work suggest that some of these hominin remains accumulated in the cave by geological processes, coming from the adjacent slope above the cave or the cave entry, as the palaeogeography and sedimentary characteristics of these allochthonous facies suggest.

Neandertal roots: Cranial and chronological evidence from Sima de los Huesos.

Seventeen Middle Pleistocene crania from the Sima de los Huesos site (Atapuerca, Spain) are analyzed, including seven new specimens. This sample makes it possible to thoroughly characterize a Middle Pleistocene hominin paleodeme and to address hypotheses about the origin and evolution of the Neandertals. Using a variety of techniques, the hominin-bearing layer could be reassigned to a period around 430,000 years ago. The sample shows a consistent morphological pattern with derived Neandertal features present in the face and anterior vault, many of which are related to the masticatory apparatus. This suggests that facial modification was the first step in the evolution of the Neandertal lineage, pointing to a mosaic pattern of evolution, with different anatomical and functional modules evolving at different rates.

The Early-Middle Pleistocene environmental and climatic change and the human expansion in Western Europe: A case study with small vertebrates (Gran Dolina, Atapuerca, Spain).

The dispersal of hominins may have been favored by the opening of the landscape during the Early-Middle Pleistocene transition (EMP) in Western Europe. The structure of the small-vertebrate assemblages of the archaeo-paleontological karstic site of Gran Dolina in Atapuerca (Burgos, Spain) shows important environmental and climatic changes in the faunal succession, across the Matuyama-Brunhes boundary at 780 ka. These changes are interpreted to indicate impoverishment of the forests, along with an increase in dry meadows, and open lands in general that entailed a tendency towards the loss of diversity in small-vertebrate communities above the EMP. We evaluate variation in diversity of the faunal succession of Gran Dolina using Shannon's Second Theorem as an index of ecosystem structure. The long cultural-stratigraphic sequence of Gran Dolina during the EMP is somewhat similar in its completeness and continuity to that in the locality of Gesher Benot Ya'aqov in the Upper Jordan Valley. We also evaluate related data including faunal and floral (pollen) succession. Both localities present cold, dry and humid, warm fluctuations at the transition between the Early and the Middle Pleistocene. Comparisons between these sites present opportunities to understand large-scale climatic changes.

Luminescence chronology of cave sediments at the Atapuerca paleoanthropological site, Spain.

Ascertaining the timing of the peopling of Europe, after the first out-of-Africa demographic expansion at the end of the Pliocene, is of great interest to paleoanthropologists. One of the earliest direct evidences for fossil hominins in western Europe comes from an infilled karstic cave site called Gran Dolina at Atapuerca, in a stratum approximately 1.5m below the Brunhes-Matuyama (B-M) geomagnetic boundary (780ka) within lithostratigraphic unit TD6. However, most of the meters of fossil- and tool-bearing strata at Gran Dolina have been difficult to date. Therefore, we applied both thermoluminescence (TL) and infrared-stimulated-luminescence (IRSL) multi-aliquot dating methods to fine-silt fractions from sediment samples within Gran Dolina and the nearby Galería cave site. We also applied these methods to samples from the present-day surface soils on the surrounding limestone hill slopes to test the luminescence-clock-zeroing-by-daylight assumption. Within the uppermost 4m of the cave deposits at Gran Dolina, TL and paired TL and IRSL ages range stratigraphically from 198+/-19ka to 244+/-26ka. Throughout Gran Dolina, all luminescence results are stratigraphically self-consistent and, excepting results from two stratigraphic units, are consistent with prior ESR-U-series ages from progressively deeper strata. Thermoluminescence ages culminate at 960+/-120ka approximately 1m below the 780ka B-M boundary. At Galería, with one exception, TL and IRSL ages range stratigraphically downward from 185+/-26ka to 503+/-95ka at the base of the lowermost surface-inwash facies. These results indicate that TL and (sometimes) IRSL are useful dating tools for karstic inwash sediments older than ca. 100ka, and that a more accurate chronostratigraphic correlation is now possible among the main Atapuerca sites (Gran Dolina, Galería, Sima de los Huesos). Furthermore, the oldest TL age of ca. 960ka from Gran Dolina, consistent with biostratigraphic and paleomagnetic evidence, implies a probable numeric age of 900-950ka for the oldest hominin remains ( approximately 0.8m below the TL sample). This age window suggests a correspondence to Marine Isotope Stage (MIS) 25, a relatively warm and humid interglaciation.

Human hyoid bones from the middle Pleistocene site of the Sima de los Huesos (Sierra de Atapuerca, Spain).

This study describes and compares two hyoid bones from the middle Pleistocene site of the Sima de los Huesos in the Sierra de Atapuerca (Spain). The Atapuerca SH hyoids are humanlike in both their morphology and dimensions, and they clearly differ from the hyoid bones of chimpanzees and Australopithecus afarensis. Their comparison with the Neandertal specimens Kebara 2 and SDR-034 makes it possible to begin to approach the question of temporal variation and sexual dimorphism in this bone in fossil humans. The results presented here show that the degree of metric and anatomical variation in the fossil sample was similar in magnitude and kind to living humans. Modern hyoid morphology was present by at least 530 kya and appears to represent a shared derived feature of the modern human and Neandertal evolutionary lineages inherited from their last common ancestor.

Dental evidence on the hominin dispersals during the Pleistocene.

A common assumption in the evolutionary scenario of the first Eurasian hominin populations is that they all had an African origin. This assumption also seems to apply for the Early and Middle Pleistocene populations, whose presence in Europe has been largely explained by a discontinuous flow of African emigrant waves. Only recently, some voices have speculated about the possibility of Asia being a center of speciation. However, no hard evidence has been presented to support this hypothesis. We present evidence from the most complete and up-to-date analysis of the hominin permanent dentition from Africa and Eurasia. The results show important morphological differences between the hominins found in both continents during the Pleistocene, suggesting that their evolutionary courses were relatively independent. We propose that the genetic impact of Asia in the colonization of Europe during the Early and Middle Pleistocene was stronger than that of Africa.

A geometric morphometric analysis of hominin upper first molar shape.

Recent studies have revealed interesting differences in upper first molar morphology across the hominin fossil record, particularly significant between H. sapiens and H. neanderthalensis. Usually these analyses have been performed by means of classic morphometric methods, including the measurement of relative cusp areas or the angles defined between cusps. Although these studies have provided valuable information for the morphological characterization of some hominin species, we believe that the analysis of this particular tooth could be more conclusive for taxonomic assignment. In this study, we have applied geometric morphometric methods to explore the morphological variability of the upper first molar (M(1)) across the human fossil record. Our emphasis focuses on the study of the phenetic relationships among the European middle Pleistocene populations (designated as H. heidelbergensis) with H. neanderthalensis and H. sapiens, but the inclusion of Australopithecus and early Homo specimens has helped us to assess the polarity of the observed traits. H. neanderthalensis presents a unique morphology characterized by a relatively distal displacement of the lingual cusps and protrusion in the external outline of a large and bulging hypocone. This morphology can be found in a less pronounced degree in the European early and middle Pleistocene populations, and reaches its maximum expression with the H. neanderthalensis lineage. In contrast, modern humans retain the primitive morphology with a square occlusal polygon associated with a round external outline.

New Neandertal remains from Cova Negra (Valencia, Spain).

New Neandertal fossils from the Mousterian site of Cova Negra in the Valencia region of Spain are described, and a comprehensive study of the entire human fossil sample is provided. The new specimens significantly augment the sample of human remains from this site and make Cova Negra one of the richest human paleontological sites on the Iberian Peninsula. The new specimens include cranial and postcranial elements from immature individuals and provide an opportunity to study the ontogenetic appearance of adult Neandertal characteristics in this Pleistocene population. Children younger than 10 years of age constitute four of the seven minimum number of individuals in the sample, and this relative abundance of children at Cova Negra is similar that in to other Neandertal sites in Europe and southwest Asia. The recognition of diagnostic Neandertal features in several of the specimens, as well as their western European context and late Pleistocene age, suggests that all the human remains from Cova Negra represent Neandertals. The archaeological evidence from Cova Negra indicates sporadic, short-term occupations of the site, suggesting a high degree of mobility among Neandertals.

Hominin lower second premolar morphology: evolutionary inferences through geometric morphometric analysis.

Mandibular premolars are increasingly used in taxon-specific diagnostic analyses of hominins. Among the principal difficulties in these evaluations is the absence of discrete, discernible, and comparable anatomical structures for rigorous quantitative assessment. Previous research has addressed either internal crown surface features (such as cusps and fossae) or the morphology of the crown outline. In the present paper, we integrate both types of information in the examination of morphological variation of lower P4s (n = 96) among various fossil hominin species with an emphasis on genus Homo. We use a set of 34 2D landmarks combining coordinate data from four classical dental landmarks on the occlusal surface and 30 sliding semilandmarks of the crown outline. Our results indicate that external shape variation is closely related to the configuration of the occlusal morphological features and influenced by dental size. The external and internal shapes of P4 are polymorphic but still useful in depicting a primitive-derived gradient. The primitive pattern seems to have been an asymmetrical contour with a mesially displaced metaconid, development of a bulging talonid, and a broad occlusal polygon. The trend toward dental reduction during the Pleistocene produced different morphological variants with a reduced occlusal polygon and decreased lingual occlusal surface in later Homo species. Homo heidelbergensis/neanderthalensis have fixed plesiomorphic traits in high percentages, whereas in modern humans a symmetrical outline with a centered metaconid and talonid reduction evolved.

A Neandertal mandible from the Cova del Gegant (Sitges, Barcelona, Spain).

A human mandible from the site of Cova del Gegant is described here for the first time and compared with other Middle and Upper Pleistocene representatives of the genus Homo from Europe and Southwest Asia. The specimen was recovered from sediments which also yielded Mousterian stone tools and Pleistocene fauna. The preserved morphology of the mandible, particularly in the region of the mental foramen, clearly aligns it with the Neandertals, making the Cova del Gegant the only known site in Catalonia documenting diagnostic human skeletal remains in association with Middle Paleolithic stone tools. This represents an important new addition to the human fossil record from the Iberian Peninsula and joins the Bañolas mandible in documenting the course of human evolution in the northern Mediterranean region of Spain.

An Early Pleistocene hominin mandible from Atapuerca-TD6, Spain.

We present a mandible recovered in 2003 from the Aurora Stratum of the TD6 level of the Gran Dolina site (Sierra de Atapuerca, northern Spain). The specimen, catalogued as ATD6-96, adds to the hominin sample recovered from this site in 1994-1996, and assigned to Homo antecessor. ATD6-96 is the left half of a gracile mandible belonging to a probably female adult individual with premolars and molars in place. This mandible shows a primitive structural pattern shared with all African and Asian Homo species. However, it is small and exhibits a remarkable gracility, a trait shared only with the Early and Middle Pleistocene Chinese hominins. Furthermore, none of the mandibular features considered apomorphic in the European Middle and Early Upper Pleistocene hominin lineage are present in ATD6-96. This evidence reinforces the taxonomic identity of H. antecessor and is consistent with the hypothesis of a close relationship between this species and Homo sapiens.

Auditory capacities in Middle Pleistocene humans from the Sierra de Atapuerca in Spain.

Human hearing differs from that of chimpanzees and most other anthropoids in maintaining a relatively high sensitivity from 2 kHz up to 4 kHz, a region that contains relevant acoustic information in spoken language. Knowledge of the auditory capacities in human fossil ancestors could greatly enhance the understanding of when this human pattern emerged during the course of our evolutionary history. Here we use a comprehensive physical model to analyze the influence of skeletal structures on the acoustic filtering of the outer and middle ears in five fossil human specimens from the Middle Pleistocene site of the Sima de los Huesos in the Sierra de Atapuerca of Spain. Our results show that the skeletal anatomy in these hominids is compatible with a human-like pattern of sound power transmission through the outer and middle ear at frequencies up to 5 kHz, suggesting that they already had auditory capacities similar to those of living humans in this frequency range.

Rates of anterior tooth wear in Middle Pleistocene hominins from Sima de los Huesos (Sierra de Atapuerca, Spain).

This study presents quantitative data on the rates of anterior tooth wear in a Pleistocene human population. The data were obtained for the hominin sample of the Sima de los Huesos site in Atapuerca, Spain. The fossil record belongs to a minimum of 28 individuals of the same biological population, assigned to the species Homo heidelbergensis. We have estimated the original and the preserved crown height of the mandibular incisors (I1 and I2) of 11 individuals, whose age at death can be ascertained from the mineralization stage and tooth eruption. Results provide a range of 0.276-0.348 and 0.288-0.360 mm per year for the mean wear rate of the mandibular I1 and I2, respectively, in individuals approximately 16-18 years old. These data suggest that incisors' crowns would be totally worn out toward the fifth decade of life. Thus, we expect the life expectancy of this population to be seriously limited. These data, which could be contrasted with results obtained on hominins at other sites, could be of interest for estimating the death age of adult individuals.

Human remains from Valdegoba Cave (Huérmeces, Burgos, Spain).

Systematic excavations, begun in 1987, at the Valdegoba cave site in northern Spain have yielded the remains of five individuals associated with a Middle Paleolithic stone tool technology and Pleistocene fauna. A fragmentary mandible of an adolescent (VB1), preserving nearly a full set of teeth, exhibits a symphyseal tubercle and slight incurvatio mandibulae anterior on the external symphysis. Both the superior and inferior transverse tori are present on the internal aspect. A second individual (VB2) is represented by a set of ten deciduous teeth consistent with an age at death of 6-9 months. A proximal manual phalanx (VB3) displays a relatively broad head, a characteristic which is found in both Neandertals, as well as European Middle Pleistocene hominids. VB4 is a fourth metatarsal that lacks the distal epiphysis, indicating it comes from an adolescent individual, and has a relatively high robusticity index. Finally, VB5 is a fifth metatarsal of an adult. The VB1 mandible shows a combination of archaic characteristics as well as more specific Neandertal morphological traits. The VB2 deciduous teeth are very small, and both the metrics and morphology seem more consistent with a modern human classification. The postcranial elements are undiagnostic, U-Th dating has provided an age of >350 ka for the base of the sequence and a date of <73.2+/-5 ka for level 7, near the top. Faunal analysis and radiometric dates from other nearby Mousterian sites suggests that the Valdegoba site is correlative with oxygen isotope stages 3-6 on the Iberian peninsula, and an Upper Pleistocene age for the Valdegoba hominids seems most reasonable.

On the age of the hominid fossils at the Sima de los Huesos, Sierra de Atapuerca, Spain: paleomagnetic evidence.

We report new paleomagnetic data for the Middle Pleistocene hominid-bearing strata in the Sima de los Huesos, North Spain. Sediments (brown muds with human and bear fossils and the underlying sterile clayey and sandy unit) preserve both normal and reversed magnetic components. The sterile unit has exclusively reversed magnetization, dating back to the Matuyama Chron, and thus is Lower Pleistocene in age. The overlying fossiliferous muds have a dominant normal magnetization that overprints a partially resolved reversed magnetization. These data are compatible with one of the reversal events that occurred during the Brunhes Chron. Combined with the existing U-series dates and evidence from the macro- and microfauna, these paleomagnetic results suggest an age of the hominid fossils between 325 to 205 ka, whereas the underlying sand and silts are older than 780 ka.

Cranial discrete traits in the middle pleistocene humans from Sima de los Huesos (Sierra de Atapuerca, Spain). Does hypostosis represent any increase in "ontogenetic stress" along the Neanderthal lineage?

Cranial discrete traits may be regarded as markers of dynamic responses to general and local perturbations of the morphogenetic pattern, particularly when they are viewed and examined in terms of hypostosis vs. hyperostosis. There are indications, in fact, that the variation between these two opposite conditions relates to mechanical stress suffered by the bony structures during early stages of growth and development. In a previous comparison between Neanderthals and modern humans, variable degrees and contrasting distribution patterns of hypostosis were found [Manzi et al. (1996), JHE30: 511-527]. In the present paper, the occurrence, expression and cranial distribution of 20 hypo-hyperostotic traits are examined in the Middle Pleistocene sample from Atapuerca - Sima de los Huesos (Spain), with the principal aim being to test whether or not the degree of cranial hypostosis increases during the evolution of the Neanderthals. Other Middle Pleistocene representatives of the genus Homo (Kabwe and Petralona), the Italian Neanderthals, and a large recent European sample are also considered. A general consistency between the gradual appearance and stabilization of the Neanderthal cranial features and the results of the present analysis is found and is interpreted as an indication that hypostosis does mark the occurrence of "ontogenetic stress". As suggested more than half a century ago by S. Sergi, an increase in "ontogenetic stress" in the Neanderthal lineage could result from the relationship between intracranial pressures and other (heterochronic) effects produced by the growth of a large brain (encephalization) and the ossification of an archaic (platycephalic) cranial vault.

Earliest humans in Europe: the age of TD6 Gran Dolina, Atapuerca, Spain.

Hominid remains found in 1994 from the stratified Gran Dolina karst-filling at the Atapuerca site in NE Spain were dated to somewhat greater than 780 ka based on palaeomagnetic measurements, making these the oldest known hominids in Europe (sensu stricto). We report new ESR and U-series results on teeth from four levels of the Gran Dolina deposit which confirm the palaeomagnetic evidence, and indicate that TD6 (from which the human remains have been recovered) dates to the end of the Early Pleistocene. The results for the other levels are consistent with estimates based mainly on microfaunal evidence, and suggest that TD8, TD10 and TD11 date to the Middle Pleistocene.

Carnivores from the Early Pleistocene hominid-bearing Trinchera Dolina 6 (Sierra de Atapuerca, Spain).

The carnivores from Trinchera Dolina level 6 (TD6) in Sierra de Atapuerca include Ursus sp., Crocuta crocuta, Mustela palerminea, Lynx sp., Canis mosbachensis and Vulpes praeglacialis. Approximately 80 human remains belonging to Homo antecessor were found in the Aurora Stratum (AS): located in the upper part of the TD6 level (TD6, T36-43). The carnivores from AS are taxonomically similar to the rest of the TD6 level, differing only in the occurrence of Lynx sp. The spotted hyaena (Crocuta crocuta) inhabited the Atapuerca Sierra during the Early Pleistocene and up to the Middle Pleistocene, after which it is absent. According to palaeomagnetic, U/Th and ESR results, the fossils from TD6 are dated to the Early Pleistocene, which is the earliest certain occurrence in Europe of Crocuta crocuta. It is associated with Mimomys savini, the arrival of which in Europe can be correlated with the beginning of the Early Biharian. Crocuta crocuta may have arrived during the late Early Pleistocene ("Bavelian complex"), and subsequently invaded the rest of the continent during the Middle and Late Pleistocene. Atapuerca TD6-AS represents the most ancient deposits in Europe where Homo and spotted hyaenas coexisted and, they probably competed ecologically. The carnivores from TD6 are biochronologically consistent with the end of the Early Pleistocene or early Cromerian (corresponding with the Biharian biochron). The timespan could correspond with oxygen isotope stages 19, 20 or 21.

The human cranial remains from Gran Dolina Lower Pleistocene site (Sierra de Atapuerca, Spain).

In this article we study the cranial remains of the late Lower Pleistocene human fossils from Gran Dolina (Sierra de Atapuerca, Spain), assigned to the new species Homo antecessor. The cranial remains belong to at least five individuals, both juveniles and adults. The most outstanding feature is the totally modern human morphology of the very complete face ATD6-69, representing the earliest occurrence of the modern face in the fossil record. The Gran Dolina fossils show in the face a suite of modern human apomorphies not found in earlier hominids nor in contemporary or earlier Homo erectus fossils. There are also traits in the Gran Dolina fossils shared with both Neandertals and modern humans, which reinforce the hypothesis that Neandertals and modern humans form a clade, and that the Gran Dolina fossils are a common ancestor to both lineages.

Axial and appendicular skeleton of Homo antecessor.

The human trunk and limb bones recovered from the Gran Dolina site, in the Sierra de Atapuerca (Burgos, Spain) are studied. All these fossils were excavated at the level called TD6 between 1994 and 1995 and have been dated in excess of 780,000 years ago. These remains have been recently attributed to a new Homo species named Homo antecessor. Axial (vertebrae and ribs) and part of the appendicular (clavicles, radii, femur and patellae) skeleton are studied here. Hand and foot bones have been studied elsewhere (Lorenzo et al., 1999). Four is the minimum number of individuals represented by the postcranial remains recovered up to now. All elements are briefly described anatomically, measured and compared with other fossil hominids and modern humans in order to establish, as far as possible, what postcranial morphology characterized this new species of our genus. The H. antecessor postcrania, generally, display a set of morphological traits that are more similar to modern humans than to the Middle and Upper Pleistocene European hominids. Our results do not contradict the previous phylogenetic analysis, i.e., that H. antecessor represents the last common ancestor for H. sapiens (modern humans) and H. neanderthalensis (Neandertals).