Remarks on the archaeological and ... - Springer Link

HUMAN EVOLUTION

Arribas A. Museo Geominero, Instituto Tecnol6gico Geominem de Espafta (ITGE). Rs Rosas, 23. 28003 Madrid, Spain. E-mail: [email protected]

Palmqvist E Departamento de Geologfa y Ecologfa (t~rea de Paleontologfa), Facultad de Ciencias, Campus Universitario de Teatinos. 29071 Mdlaga, Spain. E-mail: [email protected]

Keywords: VM-0, BL5-0, Venta Micena, Barranco Le6n, Fuente Nueva, lower Pleistocene, faunal dispersal events, lithic artefacts.

Vol. 17 - n. 1-2 ( 5 5 - 7 8 ) - 2 0 0 2

The first human dispersal to Europe: remarks on the archaeological and palaeoanthropological record from Orce (Guadix-Baza basin, southeastern Spain) The chronology of the first arrival of Homo in Europe is a rather controversial issue, with most scholars claiming until very recently that there were no permanent human settlements before the middle Pleistocene. However, new findings at Atapuerca, Dmanisi and Orce, as well as the re-evaluation of the evidence from Java, Israel and China indicate a protracted chronology for the arrival of hominids in Eurasia, during late Pliocene/lower Pleistocene times. The systematic study of the macrovertebrate assemblages from circummediterranean sites such as Orce and Dmanisi has shown a faunal replacement at the Plio-Pleistocene boundary, marked by the arrival in Europe of African immigrants such as the hippopotamus, an equid similar to modem grevy's zebra, a large cercopithecoid and several carnivores, including a giant hyaena, a sabre-tooth and a wild dog. An analysis of the relative frequency of bones and teeth for those species of large mammals preserved in Venta Micena indicates the improbability that Homo sp. is represented in the fossil assemblage by several bones and no tooth remain. Finally, new data on the stratigraphy of Barranco Le6n are offered, with remarks on the discovery in this locality of lithic artefacts and molar tooth fragment BL5-0.

Introduction: the evidence for the first human arrival in Europe The chronology of the first human colonization of Europe has generated a long and persistent debate during the last decade (e.g., Carbonell & Rodriguez, 1994; Roebroeks & Kolfschoten, 1994, 1995). Until very recently most palaeoanthropologists and prehistorians claimed that there were no permanent human settlements before 0.6-0.4 M.yr. (e.g., Arago, Bilzingsleben, Boxgrove, Fontana Ranuccio, Mauer, Sch6ningen), with most evidences concentrating on less than 0.3 M.yr. (e.g., Atapuerca Sima de los Huesos, Petralona, Swanscombe, Steinheim, Tautavel). However, new fmdings as well as the biostmtigraphical and geochronological re-evaluation o f the evidence already available suggest an early arrival of hominids in Asia, during late Pliocene times; such evidence covers a wide geographical fringe, from Israel (Erq-el-Ahrnar, 'Ubeidiyah, Yiron) (Bar-Yosef, 1994; Tchernov, 1999), Georgia (Dmanisi) (Gabunia & Vekua, 1995; Gabunia et al., 2000), the Indian subcontinent (Pabbi Hills, Riwat) (Rendell et al., 1987; Dennell et al., 1988), Java (Mojokerto, Sangiran) (Swisher et al., 1994), and China (Gonqwangling, Jianshi, Longuppo, Luonan, Yuanmon) (Zhisheng & Chuankun, 1989; Wampo et al., 1995).

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ARRIBAS,PALMQVIST

On the other hand, recent archaeological and palaeoanthropological discoveries in several sites placed close to or below the Bruhnes-Matuyama polarity reversal from Italy (Ceprano) (Ascenzi et al., 1996) and Spain, such as Atapuerca Gran Dolina (Carbonell, Bermfdez de Castro et al., 1995; Bermrdez de Castro et al., 1997), Cueva Victoria (Palmqvist, Prrez-Claros et al., 1996) and Orce (Martinez-Navarro et al., 1997; Arribas & Palmqvist, 1999), are providing an emerging picture of a continued human settlement in Europe at the end of the lower Pleistocene. The latter findings, particularly the discoveries in Atapuerca, have forced several researchers who defended the "short chronology" for the first human arrival in Europe (i.e., that no significant habitation took place before 0.5 M.yr.) to change their view towards an early occupation of Europe (Carbonell, Mosquera et al., 1995, 1999; Dennell & Roebroeks, 1996). Several sites located within the Orce-Venta Micena sector of the Guadix-Baza Basin (province of Granada, southeastern Spain) have provided some fossil remains which have been tentatively attributed to the hominids (e.g., skull fragment VM-0 and humeral shaft VM-1960 from Venta Micena, molar tooth fragment BL5-0 from Barranco Le6n-5) (Gibert et al., 1998; Gibert, Campillo et al., 1999; Gibert, Gibert, Albadalejo et al., 1999; S~inchez et al., 1999). Complementarily, two important tool assemblages (Fuente Nueva-3 and Barranco Le6n-5 sites) (Tixier et al., 1995; Turq et al., 1996; Martinez-Navarro et al., 1997; Oms et al., 2000) contribute new evidence of human presence in southern Spain during the lower Pleistocene. The human affmities of the palaeoanthropological remains from Venta Micena have instigated a long and persistent controversy during the past two decades (for review and references, see Palmqvist, 1997; Cela-Conde, 1999; Gibert, Campillo et al., 1999). The basal tool assemblage from Fuente Nueva-3 (FN-3) is less problematic, however, and includes more than one hundred pieces composed of limestone cobbles and knapped flint, showing an Oldowan Developed technology (Turq et al., 1996). The stone tools are associated with a faunal assemblage of lower Pleistocene mammals, which is similar in composition to that of Venta Micena. According to palaeomagnetic analysis (Oms et al., 2000), the whole FN-3 section is included within a reversed polarity interval. The faunal assemblage indicates that they are placed within the Matuyama chron; specifically, the presence ofAllophayomis bourgondiae indicates that the age of the palaeolithic assemblage preserved at FN-3 is slightly older than 1.07 M.yr., the lower limit of the Jaramillo normal subchron (Martinez-Navarro et al., 1997; Arribas & Palmqvist, 1999; Oms et al., 2000). Implements localized in both FN-3 and Atapuerca-TD lower levels are characterized by the following features (Carbonell et al., 1999): (i) total absence of large flakes and, hence, of tools such as handaxes, cleavers, and picks; (ii) main production of small flakes with cutting edges; (iii) main application of orthogonal methods to reduce the cores from different knapping surfaces orthogonally positioned, although unipolar and centripetal methods are already present; and, (iv) raw materials with a local origin, being flint dominant in FN-3 and flint, quartzite, and limestone in Atapuerca Gran Dolina.

The palaeoanthropologieal record from Venta Micena: fact or artefact?

Systematic excavations made at the Venta Micena quarry from 1982 onwards have provided nearly 15,000 fossils of large mammals, of which three have been tentatively classified as Homo sp. (for review and references, see Gibert, Campillo et al., 1999). These fossil remains include a small bone skull fragment (VM-0), a humeral diaphysys (VM-1960) of a juvenile individual, and a humeral fragment (VM-3691) of an adult individual. There are many reports

THE FIRST HUMAN DISPERSAL TO EUROPE

57

and articles dealing with VM-0 (the most relevant of them are reviewed below), but the humeral shafts were unpublished until the recent anatomical studies by Gibert, Campillo et al. (1999) and by SS.nchez et al. (1999), which stress the human affinities of these specimens, based on comparative analisis of computerized axial tomographs of humeral shaft cross-sections; however, it has been suggested that VMq960 could be a rib of the large scimitar-cat Homotherium latidens (S. Moy~-Sol~, pers. comm. to P. Palmqvist, August 1996). Cranial fragment VM-0 measures between 7.5 and 9 cm in diameter, and comprises part of the two parietal bones and the upper occipital squama. The wide curvature of this skull bone, the length of the sagittal suture (>6 cm), and the angle that it forms with the lamboid sutures (-120~ suggested to Gibert et al. (1983) that this fossil belonged to a juvenile individual of Homo sp. However, this conclusion was reached on the basis of the exocranial morphology, because the inner surface of the fossil was covered by a very cemented calcareous sediment. Subsequent cleaning of the endocranium revealed small, deep digital impressions and wellmarked transversal sulci, a 6 mm height sagittal crest on the occipital bone, and the trace of a coronal or fronto-parietal suture. Such atypical features led Agusti & Moyfi-Sol~ (1987) to consider that the fossil belonged to an equid of less than 3-4 months of age, although Gibert et al, (i989) reaffirmed its hominid attribution after comparative anatomical study. It is interesting to note that a sagittal crest is also present in a conclusively identified human fossil, the holotype of Homo erectus from Trinil (Martinez-Navarro, 1996). In a recent article, Moy~-Sol~ & K0hler (1997) reanalyse the morphological evidence available and conclude that this specimen was part of the cranial vault of an immature individual ofEquus altidens, the species which is better represented in the faunal assemblage from Venta Micena (Palmqvist et al., 1996). The main evidence used by Moy~-Solfi & K0hler (1997) to reach this conclusion is the presence of the coronal suture, which is particularly well preserved in the internal surface of the cranial vault; this suture runs only 4 cm from lambda, crossing perpendicularly the sagittal suture. If this interpretation proved correct, it would be key for the taxonomic assignment of VM-0, since a parietal length of only 4 cm would make attribution to Homo impossible. However, such "coronal suture" is clearly a diagenetic fracture due to sediment pressure, which perhaps was developed on a previous suture (whose structure and development was, in such case, completely masked). In fact, nearly all bones preserved at Venta Micena show orthogonal fractures produced by the diagenetic compaction of the sediment (Arribas & Palmqvist, 1998). Alternatively, Martinez-Navarro (1996) indicates that the "suture" was caused by desquamations of the inner cortical bone, as revealed by radiograph images of the fossil. Given the limitations of anatomical studies to resolve the human vs. equid affinities of this bone skull fragment, other methodological approaches were used, including the morphometric analysis of cranial sutures and the search for preserved proteins: Suture complexity was evaluated using the fractal dimension of a drawing made by Dr. J. Gibert, which revealed that the contour of the sagittal and right lambdoid ectocranial sutures were nearly linear, similar in complexity to those of modern and Plio-Pleistocene hominids (Gibert & Palmqvist, 1995). However, this drawing was over-simplified, and an accurate tracing of these sutures made by Dr. S. Moyg-Sol~ revealed a high number of small-scale fmgerings (Palmqvist, 1997: Fig. 1); the new fractal analysis provided a revised higher t~actal dimension value, which is well above the highest value obtained by Gibert & Palmqvist (1995) for juvenile individuals of Homo, and similar to those of young equids (Palmqvist, 1997). Fossil proteins (albumin and immunoglobin) have been detected by two independent ana-

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ARRIBAS,PALMQVIST

lyst teams at the University of California, San Francisco, and at the University of Granada in samples of bone tissue from VM-0, VM-1960 and VM-3961, using enzyme-linked immunoabsorbant assay (ELISA), dott-blotting, and radioimmunoassay (R/A) (Borja, 1995; Borja et al., 1997; Gibert et al., 1998; Lowenstein et al., 1999). Specifically, the albumin from VM-0 and VM-1960 was immunologically closer to human albumin than to equid albumin. However, one of the equid samples (VM-1653) used as test control yielded a significant reactivity with human anti-albumin, providing an estimated concentration in the fossil extract of 4 ng/ml of human albumin and 11 ng/ml of equid albumin (Lowenstein et al., 1999: Table 1). In addition, Dr. J. Lowenstein reported in an International Congress of Human Paleontology (Orce, September 1995) that one horse metacarpal (VM-79) used as test sample in R/A provided a much stronger reaction for human albumin (34 ng/ml detected) than for equid albumin (10 ng/ml) (Lowenstein, 1995); surprisingly, this sample is not included in the article published recently by Lowenstein et al. (1999) in Human Evolution. The obtaining of such contradictory results opens the possibility that the samples were contaminated. In addition, several studies (Cattaneo et al., 1993; Fiedel, 1996; Tuross et al., 1996) put a cautionary note on the viability of palaeoimmunologic analyses, stressing the contradictory results obtained in many studies of proteins recovered from fossil bones and blood residues from stone tools using ELISA and RIA. A third approach to this problem is offered here, estimating the probability that a taxon of the size of Homo sp. (i.e., -50 kg) could be represented in the faunal assemblage from Venta Micena by several bones and no tooth remain. The palaeontological collection from this site (Arribas, 1999) is composed of a number of identifiable specimens (NISP) of 5,801 (3,015 dental elements and 2,786 bones). These specimens allow calculation of a minimal number of individuals (MN/) of 227, which belong to 20 taxa of large (>5 kg) mammals: Mammuthus meridionalis, Hippopotamus antiquus, Bovini cf. Dmanisibos, Soergelia minor, Praeovibos sp., Hemitragus alba, Eucladoceros giuliL Pseudodama sp., Stephanorhinus etruscus, Equus altidens, Hystrix major, Homotherium latidens, Megantereon whitei, Lynx aft. issiodorensis, Pachycrocuta brevirostris, Canis (Xenocyon) falconerL Canis etruscus, Vulpespraeglacialis, Ursus etruscus, and cf. Meles. The bone assemblage includes also 656 indetermined specimens that could not be assigned to one of the taxa listed above, such as small fragments of bone diaphyses and cranial vaults (felidae: 24, carnivora: 23, artiodactyla: 112, herbivore: 409, mammal indet.: 88), and -10,000 unidentifiable bone shafts. Tooth remains and elements l~om the postcranial skeleton of the following species of small mammals are also present in the faunal assemblage: ,41lophaiomys pliocaenicus, Apodemus aft. mystacinus, Castillomys crusafonti spp., Eliomis intermedius, Desmana sp., Prolagus capensis and Oryctolagus cf. lacosti (Agusti, Arbiol et al., 1987). Taphonomic analysis of the bone assemblage (Arribas et al., 1996; Palmqvist et al., 1996; Arribas & Palmqvist, 1998; Palmqvist & Arribas, 2000) revealed that most skeletal remains of large mammals were scavenged by the giant hyaena P. brevirostris from carcasses of animals hunted selectively by hypercamivores, such as sabre-tooths (H. latidens and M. whitei) and wild dogs (C. falconeri). Adult hyaenas transported ungulate carcasses and body parts to their maternity dens as a function of the mass of the ungulates scavenged: species of300 kg the hyaenas preferentially transported the limbs, which provide high marrow yields. Given that long bones are subject to destruction by hyaenas for accessing their marrow cavities, this implies that small-to-medium sized species are comparatively better represented in the assemblage by teeth than by bones, as shown in Fig. 1.


59

The fracturing by hyaenas of limb bones in the dens was highly selective, correlating with marrow content and mineral density (Arribas et al., 1996; Arribas & Palmqvist, 1998). Biostratinomic fractures are very abundant, since only 5 specimens, with the exception of the porcupine (H. major), identified from a maxilla, and the mustelid (cf. Meles), represented by a distal humerus and a fragment of a canine tooth. The most abundant taxa range in estimated adult mass between 150 and 400 kg, and are represented by 3,898 specimens (1,979 teeth, 1,919 bones); the abundance of skeletal remains from species of small body size (15,000 fossils unearthed during systematic excavations in the Venta Micena quarry, no tooth remain of hominids has been yet discovered in this palaeontological locality. This argues strongly against the possibility that the three bones considered by Gibert, Campillo et al. (1999) to show human affinities could belong to Homo sp.

The archaeological record from Barranco Le6n-5: stratigraphie context, age, and finding of molar tooth fragment BL5-0 Gibert, Gibert, Albadalejo et al. (1999) reported recently in Human Evolution on the discovery of a rather small tooth fragment (BL5-0) during systematic excavations held in August 1995 at Barranco Le6n-5, a palaeontological site located in a ravine near the village of Orce.

60

ARRIBAS, PALMQVIST

BL5-0 preserves the mesial part of the crown and root (4.6 mm crown height, 2.9 mm root length). A large wear facet is present on the crown, showing the dentine exposed. Following the comparative study of the arrangement and angles formed by the striae of Retzius and Hunter-Shreger bands, the shape of the enamel prism patterns, and the enamel thickness, Gibert, Gibert, Albadalejo et al. (1999) conclusively identify BL5-0 as an upper human molar. However, we think that several remarks on the stratigraphy of this locality are necessary, and also on the circumstances in which the finding of the tooth fragment took place. The continental sedimentary sequence within the Orce-Venta Micena sector is predominantly carbonated (Vera et al., 1985 ; Sofia et al., 1987). Until the beginning of the nineties all the palaeontological localities with mammal remains had been found in sediments from lacustrine or swampy environments, and no fossiliferous fluvial deposits were known within this sector. By such reason, the search for this type of deposits was one of the main objectives of the field work, since they would provide complementary taphonomic and palaentological information to that obtained in Venta Micena, a locality developed on a lacustrine border. However, the geological prospection for appropiate sedimentary layers was long, because the region is covered by numerous ravines distributed on a surface o f - 2 0 km2 (Fig. 2). Field work was focussed during 1992 in the analysis of the stratigraphy of Barranco Lern (BL). This ravine is North-South oriented and its headwaters are several hundred meters distant from the Mesozoic palaeogeographic height of Sierra Umbria (Fig. 3). The ravine was visited during the eighties by all members of the excavation team, since it has two localities with small mammals of lower Pleistocene age, Barranco Lern-2,3 and Barranco Le6n-1 (Agusti, Moy/t-Sol/l et al., 1987; Agusti, Moy/l-Solit & Pons-Moy/t, 1987). The sediment at these localities is composed of dark-coloured mudstones and silts rich in organic matter, which indicates deposition in a swampy environment with a rich vegetation cover. Both layers outcrop in a vertical wall, and are separated by -3 m of deposits. These deposits showed a thin covering of calcareous mud produced by weathering of the overlying sediments, which did not allow to see the original composition and structure of the covered deposits. However, a small stratum placed close to the bottom of BL-I (and previously described as fossiliferous by Vera et al., 1985) showed the crown of an equid molar tooth. The subsequent cleaning of the surface of this layer revealed that it was composed of a clastic sediment 15-35 cm thick, showing at its bottom numerous boulders, bone shafts, teeth of large mammals, and five toffee-coloured laminar chert flakes 1-6 cm long. The flakes outcropped laterally along two meters and showed evidence of tool manufacturing. In this way, the interest of the new locality relied on its palaeontological record, the potential archaeological importance and, specially, its taphonomic characteristics (fluvial taphosystem), which were completely new in this sector of the OrceVenta Micena basin. As previously exposed, there are several palaeontological localities outropping in this ravine; the stratigraphic column shows the following sedimentary evolution, from bottom to top (Figs. 4-5): - Barranco Le6n-2,3, which is a layer composed of black clays and brown limes with an average thickness of 60 cm, showing abundant lateral changes of facies to light-coloured bioclastic sands and marls. This locality was already known (Agusti, Moy~-Solit et al., 1987) and its faunal list includes the following taxa: Allophaiomyspliocaenicus, Apodemus mystacinus, Apodemus aft. sylvaticus, Castillomyscrusafonti ssp., Eliomys intermedius, Equus cf. altidens, Cervidae gen. indet, et sp. indet., Bovini gen. indet., Hemitragus alba, Soergelia minor, Hippopotamus antiquus and Mammuthus meridionalis.

61


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Figure 1. Least squares regresston analysis for the relationship between the logarithms of the relative abundance of tooth remains and the body mass (M, in kg) estimated for the adult individuals of those taxa of large mammals (N = 20) preserved in the lower Pleistoeene assemblage at Venta Mieena. The dotted lines represent the p < O.05 eonfidence interval above and below the regression line (data on abundanee of teeth~bones from Arribas & Palmqvist, 1998). The three specimens included in Hom ~ sp. (cranial fragment VM-O, humeral shaft VM-1960, and distal humerus VM-3691) are those considered to show human affinities by Gibert, Campillo et al. (1999); this taxon was not used in the adjustment of the regression line. An endoeranial view of skull fragment VM-Ofrom Venta Micena is included, showing the coronal suture/diagenetie fracture and the tentorial crest in the occipital bone.

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Figure 2. Geographic location o f the Orce-Venta Micena sector in the northeastern part o f the Guadix-Baza basin. The position o f the three lower Pleistocene localities with the most significant palaeontological (Venta Micena) and archaeological record (Barranco Le6n-5 and Fuente Nueva-3) is marked on the digital model o f the surface. The reference framework during the lower Pleistocene is an endorheic lacustrine system with waters coming from southwards, showing an emerged area around Venta Micena and savanna-type plains to the East and North. In the vicinity o f Fuente Nueva there was a swamp associated to a Mesozoic "island-mountain '" and in Barranco Le6n an episodic fluvial channel intersected the swamps near the Jurassic emerged mountains. Scale bar length represents 5 Km.


63

Figure 3. Digital models of the surface in the Orce-Venta Micena sector and aerial photograph of the region around Barraneo Le6n (1. Venta Mieena, 2. Fuente Nueva, 3. Barraneo Le6n). A and B. Views from the East and West, respectively, of the Oree- Venta Mieena sector (the direction o f the fluvial system is indicated, and also the possible source o f part of the fossils and lithic artefacts unearthed at Barranco Le6n-5). C. Aerial photograph of Barranco Le6n (3) showing the minimal distribution of subenvironments during the lower Pleistocene. A swamp developed around the ravine, and a sporadic fluvial channel with a South-North direction deposited within it the fossil remains and stone tootls o f BL-5 (the probable source areas of the lithic artefacts in the palaeoegeographic heights during the lower Pleistocene are marked in white). The palaeosoil placed to the northeast of the figure was emerged to the East o f the sector, in such way that its maximum development is found in the Venta Mieena area. Scale bar length represents 1 Km in each of the three figures.

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ARRIBAS, PALMQVIST

Figure 4. View of the stratigraphic section at Barranco Le6n, showing the position o f the locality BL-5 in the part o f the ravine where this level presents distalfacies (fine detritics; the facies are proximal 50 meters to the North, being composed by calcareous boulders >10 cm thick). The palaeontological locality BL-2,3 is placed at the bottom of the figure. BL-5 is erosive on both BL-4 and the underlying unit, showing a grain-size decreasing evolution up to BL-1, which represents the sealing deposits of the fluvial palaeochannel. The layers marked with an asterisk (BL-4 and that immediately above BL-1) are identical, both in composition and structure; this indicates that the swampy system recovered its sedimentary dynamics after the erosion produced by the channel, showing again typical central swampy facies (i.e., a subaquatic, low-energy tractive environment free o f vegetation). The numerical ranking of the fossiliferous layers follows the work o f Agustl, Moygt-Solit et al. (1987).


65

Figure 5. Hew o f Barranco Le6n before 1995 (all the area shown between BL-5 and the arrow to the left o f this layer was destroyed by the preparation o f the excavation during that year). Black arrows mark the position o f the BL-5 layer (the proximal facies showing the pebbles o f the lag-deposit are to the South [left side on this view], and the distal facies are to the North [right side on this figure]). White arrows indicate the position o f BL-2,3. t~aite stars mark the surface o f the slope where several chert flakes were found before 1992. The black star indicates the upper platform where there are abundant musterian flakes and nuclei. Up to 1992 no lithic tool was found where this layer outcrops. Vertical scale bar length represents I m.

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ARRIBAS,PALMQVIST

A layer 25 cm thick, composed of calcilutites and sands, which has not provided vertebrate remains. Barranco Letn-A, a 50 thick stratum composed of dark-colured lutites and silt. Although this layer has not been sampled systematically, there are abundant bone shafts outcropping on its surface. A 100 cm thick layer of white mudstones with no fossil content, which interdigitates with a level 45 cm thick (Barranco Letn-B) of sandy lutites with bone shafts of large mammals. A level 20 cm thick with dark-coloured lutites and silt, which does not show fossil remains. Barranco Le6n-4, a 22 cm thick stratum composed of gray mudstones with skeletal remains of large mammals, including a maxillae of Pseudodama sp., which outcrops in the southern part of the ravine. The top of this layer is erosive, being replaced in the north of the ravine by a detritic unit which outcrops along 150 m and has made dissapear the muddy stratum, totally or in part. Barranco Le6n-5, the latter detritic unit, is 22 cm thick and erosive, in such way that its bottom is in some points in contact with BL-4 and in others with the underlying lutitic level. The base of this layer is rather irregular in the proximal fringe, formed by rounded pebbles of several centimeters to decimeters of diameter, composed of Jurassic limestones and dolomites; the pebbles change northward to calcareous and muddy intraclasts, The matrix is composed of fme-grained quartz sands and lutites, with abundant shell fragments of fresh-water gastropods. As indicated before, this layer has provided lithic artefacts manufactured by the hominids (Tixier et al., 1995; Turq et al., 1996) and fossils (mainly teeth, phalanges, and vertebrae) of Oryctolagus cf. lacosti, Canis etruscus, Eucladoceros sp., Bovini indet., Hippopotamus antiquus, Equus cf. altidens and Felidae cf. Homotherium sp. There are also skin plates of Testudo sp. The genus Homo should be added to these taxa, due to the presence of ethologic structures (since the lithic tools can be considered as such; Arribas & Palmqvist, 1999). - A detritic level 35 cm thick composed of mudstones, which is structured in three decimetric sublevels where the average grain size decreases from the lower to the upper, formed by dark, brown limes with tractive sedimentary structures. Barranco Le6n-1, a stratum 20 cm thick composed of lutites and black mudstones, which shows the following assemblage of small mammals (Agusti, MoyA-SolA et al., 1987): Allophaiomys pliocaenicus and Mimomys sp. - A stratum 30 cm thick composed of gray limes homologous to those present in BL-4, which continues in sandy and calcareous sediments. The layers comprised between BL-2,3 and BL-4 indicate the sedimentation of tributary channels in a swampy palaeoenvironment, with detritic inputs from the west of the fluviallacustrine system, showing lateral changes of facies and a vertical altemance between sediments deposited in marginal environments, covered by dense vegetation, and central ones without vegetation, deposited under a shallow water sheet. On the contrary, the sedimentary layers comprised between BL-5 and BL-1, both included, represent a shallowing sequence which fills a fluvial palaeochannel, showing the erosion by the riverbed of the previous swampy deposits (BL-4). The infilling of this channel with sediment transported by the waters (which were >100 m width and -2 m deep) started with a bottom "lag" (BL-5) and fmished through a grain size decreasing sequence in a swampy sealing pond (BL-1). The erosion of the swampy sediments by the palaeochannel seems to have been produced during only one fluvial event, which erod-

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-


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ed the plain and deposited new sediments and bone remains from the South of Sierra Umbria, which are clearly allochtonous to the swamp. As a consequence, the quiet sedimentary dynamics of the swampy system were modified by the catastrophic arrival of materials from a neighbouring area which until that moment was isolated from the swampy environment by a Mesozoic rocky threshold. On the top of BL- 1 there is a new layer of gray limes, very similar to those placed below BL-5, which indicates the normalization of the sedimentary dynamics after the deposit of the sequence which filled the palaeochannel. As a consequence, BL-5 is a locality in which there is a concentration and sorting by water of fossils from animals which inhabited the swampy margin (eg., Hippopotamus antiquus), with others from the riverbed (eg., fresh-water mollusks), and also from the source area of the torrential waters (eg., Equus cf. altidens and probably also the lithic tools), which were removed from their primary context in the South of Sierra Umbria (Fig. 3). Thus, the assemblage is taphonomically reworked, and by this reason all palaeoecological and palaeoethological interpretations should be done with caution, following the appropiate taphonomic controls. What seems clear is that both the skeletal remains of large mammals and the lithic artefacts are not placed were they were produced, and there are no objective evidence of in situ human activity, contrary to what has been published by Dr. J. Gibert and his associates. On the contrary, the fossils and tools were deposited in a place where a tributary of the Orce river transported materials from different nearby environments, thus producing a biostratinomic mixing of calcareous pebbles, bones and lithic artefacts from the swampy system and from the Mesozoic heights. The evidence presented above allows us to discard the possibility that there was human activity at BL-5, since the origin of this locality was produced under an intense water sheet at least two meters depth, as corroborated by the lithology, the erosive base which affects two underlying strata with different composition, the presence of intraclasts originated from the water erosion of these strata, the abundance of Mesozoic calcareous extraclasts in the proximal facies of BL-5, the high horizontal and vertical dispersion of bone remains, the high degree of fluvial abrasion and fragmentation of fossils (in which isolated teeth and bone shafts predominate), and the low taxonomic diversity, since the most abundant species is the hippopotamus, represented by craniodental elements. However, all these features suggest that the taphonomic study of BL-5 and the overlying sedimentary units up to BL-1 would provide detailed information on the geological processes that originate fluvial deposits with archaeological and palaeontological remains. Finally, it is worth to mention some remarks on the age of BL-5. A recent publication (Oms et al., 2000) with the results obtained in a paleomagnetic study of BL-5 has revealed exclusively reverse magnetization throughout the whole stratigraphic sequence, thus indicating a Matuyama age (1.77-0.78 M.yr.) for this archaeological locality. Therefore, the previously available paleomagnetic information was clearly overestimated, since Arribas et al. (1994), Gibert et al. (1994) and Gibert, Gibert, Albadalejo et al. (1999) placed BL-5 within the Olduvai event (i.e,, 1.98-1.77 M.yr.; see Gibert, Gibert, Albadalejo et al., 1999: Fig. 2). The faunal list from this locality includes taxa indicative of a lower Pleistocene age, but allows no further biochronological precissions; however, the underlying locality is BL-2,3 and the overlying one is BL-1, the latter showing an assemblage of small mammals which could mark the limit between the Allophaiomys pliocaenicus and Mimomys savini biozones. These upper Villafranchian localities have been placed biostratigraphically above Venta Micena (Agusti & Moy~t-Solh, 1992) and below Fuente Nueva-3 (Martinez-Navarro et al., 1997). By this reason, the age of BL-5 could be placed within the middle third of the lower Pleistocene, before the

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appearance of M. savini in the Iberian palaeomastological record (Arribas & Palmqvist 1999). M. savini is associated with A. bourgondiae in Fuente Nueva-3, the younger locality of the stratigraphic column. There are also some remarks conceming molar tooth fragment BL5-0, attributed to Homo by Gibert, Gibert, Albadalejo et al. (1999). Firstly, contrary to that affirmed in the latter article, this locality was known to have a record of large mammals from the eighties decade (Vera et al., 1985; Anad6n et al., 1987: Fig. 22). By that time some members of the scientific team led by Gibert found several fragments of chert in the surface of the slope that gives access to the medial part of the Barranco Lern ravine (Fig. 5); such cherts could have been trasported by rain washing from the surface of the plain excavated by the ravine, since Magdalenian nuclei and chert flakes are abundant on this plain. During 1992 one of the authors of this article (A. Arribas) found in situ, within the stratigraphic profile of the stratum which was named later as BL-5, a set of chert flakes associated to abundant osseous remains of megaherbivores. The presence of lithic tools in the profile is constant between 1992 and 1994. In August 1994 A. Arribas took a sample (500 g) of the limes which constitute the matrix of this layer, in order to make preliminary sedimentological and microstratigraphic analyses. The subsequent washing and sieving of this sample in September 1994, in the Laboratory of Palaeontology and Mineralogy of the Museo Geominero (ITGE), revealed abundant dental fragments ofperissodactyls and ruminants, and also a tooth fragment with a maximum size of 5 mm, which in first instance seemed to have belonged to an omnivorous mammal. Given the fact that the other tooth fragments could be identified up to family level (Equidae, Cervidae, Bovidae and Leporidae), an attempt to determine this small fossil was also performed. The tooth fragment showed an advanced degree of wearing and preserved part of a root, a reduced pulp cavity, a thick enamel and the facet of contact with other tooth of the same dental series. Taking into account such features, the relative dimensions of the specimen and its microstructure, it was compared with teeth of ursids, suids and hominids, after a preliminary study which revealed that the fossil differed substantially from any deciduous or permanent tooth of ruminants and carnivores. Homologous sections of the upper and lower molariform teeth of several members of the three families of omnivorous mammals were obtained; the results showed that the structure of the small tooth fragment was analogous to the fragments of lower molar teeth of Homo sapiens used in the comparisons, According to the author's opinion, a dental fragment with such characteristics should not be published, because it does not provide relevant taxonomic information, although it must be taken into account if it really belongs to the family Hominidae, since it appeared associated to stone tools within a sedimentary layer of lower Pleistocene age. Due to this reason, the decision to show this specimen to the Spanish specialist in human dentition, Dr. J.M. Bermfidez de Castro (Museo Nacional de Ciencias Naturales, CSIC), was taken. Up to that moment, November 1994, Dr. J. Gibert did not know about this fossil, since A. Arribas wished to have the previous opinion of an expert, given the strong debate on all the palaeoanthropological remains from Orce. The tooth fragment was tentatively identified by Bermfidez de Castro as a deciduous human molar, although this specialist explained that to accurately determine the specimen was a rather difficult task, an opinion with which A. Arribas fully agreed. In addition, Dr. J. Van der Made, an expert in omnivorous mammals, remarked that the tooth fragment was quite different from the teeth of suids and very similar to those of primates. Following these considerations, the molar tooth was sent to Dr. J. Gibert with the recommendation that the importance of the locality did not rely on this fossil, but on the unusu-


69

al assemblage of large mammals and stone tools preserved in a lag-deposit within a palaeochannel. In fact, the tooth fragment only suggested the possibility that identifiable hominid remains could be found after the systematic excavation of this locality, given that it is a concentration or placers sedimentary process (sensu Seilacher et al., 1985). The first systematic excavation of this locality took place during August 1995. Therefore, the affirmation of Gibert, Gibert et al. (1999) that tooth fragment BL5-0 was found during that excavation is incorrect, since the fossil specimen comes from a sample of sediment taken from the stratigraphic profile which outcrops in the ravine and was identified the year before. The data presented above justify the quality of the geological, palaeontological and archaeological record from Orce, showing that this geographic region has preserved an exceptional evidence on the composition of the European ecosystems during the Quatemary, and also provides a first-hand source of information on the chronology and ecological circumstances of the first human dispersal from Africa to Europe.

Faunal replacement in the lower Pleistocene of Europe The major sea-level fluctuations and climatic shifts evidenced by stable isotopes provide a basis for the study of major vegetational and faunal changes in the Eurasian continent during the Plio-Pleistocene (Azzaroli, 1995; Arribas & Palmqvist, 1999). Three important sea-level drops stand out due to their translation in wide-ranging environmental changes along the continents: the Aquatraversan, the Aullan, and the Cassian erosional phases. The older of these sea-level falls, the Aquatraversan or "Elefant-Equus event", took place halfway through the Pliocene (2.6-2.4 M.yr.), being accompanied by a marked cooling of ocean waters and by wideranging changes in vegetation and faunas on the continents (the transition from the warm Reuverian to the cooler Praetiglian in Western Europe), including the extinction of warm-forest faunal elements such as zygodont mastodon (Anancus avernensis) and tapir (Tapirus arvernensis), and the arrival from Asia of elephants (Mammuthus meridionalis) and the first monodactyl equids (Equus stenonis). The second event, the Aullan (1.8-1.6 M.yr.), corresponds with a relatively minor retreat of the sea-level, and coincides with the conventional NeogeneQuaternary boundary, marking the arrival of several African immigrants to Europe, including the genus Homo, and is further discussed below. Finally, the Cassian sea-level fall (1.2-0.9 M.yr.) was also produced by a cooling of the ocean waters, affecting deeply the continental vegetation and faunas, and marks the "end-Villafranchian" dispersal event with the transition to the middle Pleistocene Galerian faunas (see review in Arribas & Palmqvist, 1999). These major climatic changes were accompanied in East Africa by a shift from mesic, closed environments to more xeric, open habitats, which was reflected in the assemblages of large mammals by a significant faunal turnover between 2.5 and 1.6 M.yr. (Behrensmeyer et al., 1997), translated in an increase of the percentage of terrestrial grazers and a parallel decline of the abundance of frugivores and species with arboreal locomotion (Reed, 1997, 1998). The systematic study of the macrovertebrate assemblages from circnmmediterranean sites such as Orce and Dmanisi has shown a faunal break at the Plio-Pleistocene boundary in the western and central fringes of Eurasia (Arribas & Palmqvist, 1999). It is also recorded in part within the Villafranchian of Italy (Olivola and Tasso faunal units), where the faunal replacement was called the "Wolf event". This break is marked by the arrival in Europe of African immigrants during the late Pliocene and the beginning of the Pleistocene, such as the hip-

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popotamus, an equid similar to modern grevy's zebra, a large cercopithecoid and several carnivore species, including a giant hyaena, a sabre-tooth, and probably also a wild dog. The first monodactyl equids are fnost recorded in North America (Hagerman Formation, Idaho) at 3.4 M.yr. by the species Equus simplicidens. The genus Equus arrived in Eurasia at -2.6 M,yr., where they are represented by the species Equus stenonis in Russia (Livezovka), Italy (Olivola, Montopoli), France (Saint Vallier, Chilhac) and Spain (Hu~lago, Rinc6n, La Puebla de Valverde). Between 2.3 and 1.4 M.yr. two species of horses with slender metapodials and phalanges than those ofE. stenonis are found in East Africa (Omo Shungura, Olduvai, East Turkana), North Africa (A~n Boucherit, A ~ Hanech) and the Middle East ('Ubeidlya). One of these species (Equus numidieus) had a large body size, comparable with that of extant Equus grevyi (i.e., -350 kg), while the other(Equus tabeti) was of smaller size, similar to Equus kiang (i.e., -200 kg). E. numidicus arrived in Europe during the Plio-Pleistocene transition (where it has been named Equus altidens) and is found in Spain (Venta Micena, C611ar de Baza, Cueva Victoria, Hu~scar-1), Italy (Pirro Nord, Selvella), France (Sainzelles) and Germany (Sfissenborn). The replacement of E. stenonis by E. altidens at the Plio-Pleistocene transition indicates a change from wet, woodland habitats to more open and dry plains (Guerrero-Alba & Palmqvist, 1997). The presence of the large African cercopithecoid Theropithecus oswaldi in the lower Pleistocene of Cueva Victoria (Murcia, Southeast Spain) (Gibert et al., 1995) constitutes an important faunal event, since the palaeogeographical distribution of this species was basically restricted to Africa until it was discovered in this karstic site, although fossils of Theropithecus have been found at Mirzapur, India (Arribas & Palmqvist, 1999). The arrival in the Old World of the genus Canis from North America took place -3.0 M.y. ago, as evidenced by the finding of Canis etruscus-like forms in deposits of this age in China. The first record of this coyote-sized species in Europe is in the Olivola faunal unit and defines the "Wolf event": Canis (Xenocyon)falconeri was a hypercamivorous canid (Palmqvist et al., 1999) scarcely recorded during the late Pliocene and early Pleistocene in the Old World. This species had a second metacarpal with a very reduced articular facet for the first metacarpal, what indicates that the latter bone was vestigial if not absent, a condition similar to that of African painted dogs, Lycaon pictus, the only extant canids with a tetradactyl forelimb. C falconeri is first recorded in China, within the upper Pliocene locality at Fan Tsun (-2.5 M.yr.). This species arrived in East Africa during Olduvai Bed I times (1.9 M.yr.), and its first record in Western Europe is in the Upper Valdamo (Tasso faunal unit, included in the upper part of the Olduvai Subchron). In spite of the Asian origin of this species, we can not rule out the possibility that it reached Europe from Africa, since its first European record matches that of other African inmigrant, Hippopotamus antiquus. However, the arrival of both species also coincides with that of others from Asia, like Canis arnensis, Praeovibos, andAllophaiomyspliocaenicus. Pachycrocuta brevirostris was a large, short-faced hyaena relatively common in lower Pleistocene European assemblages of large mammals. It had a body 20% larger than the modem spotted hyaena, Crocuta crocuta, and was well adapted for destroying carcasses and consuming bone (Palmqvist et al., t996; Arribas & Palmqvist, 1998). This species shows a relative shortening of the distal limb segments, what suggests a less cursorial life style than others hyaenids, although such shortening could provide greater power and more stability for dismembering and carrying large pieces of carcasses. P brevirostris is recorded in China from the end of the Pliocene (Nihowan) to middle Pleistocene times (Zhoukoudlan Locality I). It is found in Africa between 1.0 and 3.0 M.yr., and its arrival in Europe is recorded in upper

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71

Pliocene deposits at Olivola (-1.8 M.yr.), while the latest appearances are in early middle Pleistocene sites, like S(issenborn. In the Iberian Peninsula this species is found exclusively in early lower Pleistocene localities, and its record during middle Pleistocene times is not known. It is ditticult at present to decide ifP. brevirostris originated in Asia or in Africa; however, what seems clear is its presence in Africa when it spread in Europe during the beginning of the Eburonian event. The extinction o f P brevirostris seems to have been linked to the decline and subsequent disappearance of machairodont cats at approximately 0.5 M.yr., what implied the loss of an important source of partly-consumed carcasses, and thus a change in the interactions between flesh-eating and bone-cracking species of the carnivore guild (Arribas & Palmqvist, 1999). The earliest record of the sabre-tooth genus Megantereon is at 4.5 M.yr. in the Bone Valley Formation (Florida), where it is represented by M. cultridens. This species dispersed from North America to the Old World at 3.5-3,0 M.yr., and inhabited Europe until the lower Pleistocene; in China it lingered well into the middle Pleistocene at Choukutien Locality I (see review in Martinez-Navarro & Palmqvist, 1995). In Africa M. cultridens evolved to M. whitei, which is characterized by a reduction in the size of the maxillary carnassial (P4), the mandibular premolars (which is reflected in the appearance of a diastema between P3 and P4), and the lower camassial tooth (M1). M. whitei replaced M. cultridens in Western and Central Eurasia at the Plio-Pleistocene boundary, as recorded at Orce, ApoUonia and Dmanisi (MartinezNavarro & Palmqvist, 1996). The arrival of this carnivore in Eurasia may have played a significant role in facilitating the dispersal of Pachycrocuta and Homo outside Africa, since itwas an ambush predator that presumably left large amounts of flesh and all within-bone nutrients in the carcasses of the ungulates preyed, which could be scavenged by the hyaenas and the hominids (Arribas & Palmqvist, 1999). The data presented above indicates that a flux of African species to Eurasia took place during the end of the Plio-Pleistocene transition. Such evidence enforces the argument that Homo must have migrated into Europe at a similar stage, pertaining to a protracted European chronology. The fact that most African species are found in Southern Spain is explained if we consider that the Iberian Peninsula was faunally and climatically a part of Africa during the Neogene, far more than it was a part of Europe. This ecological approach to the first human arrival in Europe allows inclusion of the genus Homo in a faunal set which expanded its palaeogeographical range during the early Pleistocene.

Chronology and ecological context of the first human dispersal to Europe Until now, three chronological hypotheses regarding the first arrival of humans to Europe had been proposed: the Europe of 0,5 M.yr. (i.e., the "Young Europe" of Carbonell, Mosquera et al., 1995), which was widely accepted until 1994; the Europe of 1.0 M.yr. (i.e., the "Mature Europe"), which has been followed since then by most palaeoanthropologists (Carbonell et al., 1999); and the Europe of 1.5 M.yr. (i.e., the "Old Europe"), which is for us the most reliable chronological scenario. In order to decide in favour of any of them, it is necessary to answer the following question: did humans leave Africa alone or simultaneously within a set of large mammals? This question has only two possible answers (Arribas & Palmqvist, 1999): 1.- Humans left the austral continent alone. If this hypothesis proves correct, the disper-

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sal of Homo out of Africa would not depend on any extrinsic factor, but on intrinsic ones (i.e., population "saturation", technological advances in tool making). From this premise, if humans left Africa alone they could do so at any given moment from the time of their origin whenever the geographic and climatic barriers allowed them to disperse. According with the available paleoanthropological record, the oldest presence of Homo in Asia would be then restricted to 1.8-1.6 M.yr. (Java, Southern China), in the Caucasus to -1.77 M.yr. (Dmanisi, Georgia), and in Western Europe to -0.8 M.yr. (Atapuerca, Ceprano). In this case it would make no sense to consider in this discussion those aspects related with the technological level adquired by the genus Homo or with the faunal dispersal events which took place during the Plio-Pleistocene. The oldest archaeological and paleontologic evidence recovered in Southeast Spain (Orce) would not be relevant, since the information supplied by these sites points to a faunal turnover which is not detected in Atapuerca (where the record comprises species originating more recently in Asia, during the middle Galerian). In this case the arrival of Homo to Europe would be independent of other palaeobiological factors, and thus the dispersal would be monospecific. This chronological scenario has been recently envisioned by Carbonell et al. (1999), who ask the following questions: (i) why at -1 M.yr. did Mode I disperse into Europe, but not Mode II, which was already developed in several African areas?; (ii) how did Mode II technology replace Mode I in Europe (i.e., by gradual evolution or by a rupture)?; and (iii) why did Mode II industry appear in Europe so long after its origin in Africa? In an attempt to solve these problems, Carbonell et al. (1999) consider that early African humans were splitted in two groups, those which retained the Oldowan (Mode I) tools and those producing the technologically improved Acheulean (Mode II) artefacts. In their model, the dispersal to Europe took place at -1 M.yr., and involved only Mode I technology (although Mode II was already well developed in Africa from 1.4 M.yr. onwards; Asfaw et al., 1992), due to differential subsistence strategies, such as the competition for resources between Mode I- and Mode II-producing populations, which drove the former, but not the latter populations out of the Rift System to other areas. Carbonell et al. (1999) conceive Mode I technology as highly effective in succesfully facing the new Eurasian environments, and propose that when the African areas with Mode II became saturated (i.e., 0.5 M.yr. after the first dispersal at -1.0 M.yr.), the Mode II technical system started to spread, replacing Mode I technology in Eurasia long after its initial settling. However, this model of displacement in a sort of techno-discrimination scenario is a rather difficult hypothesis to prove, since it does not take into account: (i) the recent findings of Oldowan tools in the archaeological sites from Orce, with ages in excess of 1 M.yr. (MartinezNavarro et al., 1997; Oms et al., 2000); (ii) the discovery of Oldowan tools and human remains showing affmities with African H. ergaster in Dmanisi, dated at -1.77 M.yr. (Gabunia & Vekua, 1995; Gabunia et al., 2000); and (iii) the important faunal replacement in the European assemblages of large Inammals during the Plio-Pleistocene transition, which records several species of large mammals originating in Africa, including an ostrich at Dmanisi (MartinezNavarro & Palmqvist, 1995, 1996; Arribas & Pahnqvist, 1999). 2.- Humans left Africa accompanied by other animals. If this scenario is correct, the fossil record should preserve species originating in Africa within the Eurasian ecosystems of lower Pleistocene times, and the faunal turnover should concentrate on a restricted chronological interval. This hypothesis is widely corroborated by the fossil record in Europe, as discussed before. If we consider the partial faunal replacement of large mammals which took place in Europe at the Plio-Pleistocene limit ('Wolf event': Asian species, 'Homo event': immigrants from Africa), it is then possible to explain the presence of both African carnivores and

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Asian ruminants in the lower Pleistocene of the circummediterranean area, and their coexistence with members of the genus Homo showing anatomical affinities with H. ergaster, as proposed by Arribas & Palmqvist (1999) and recently evidenced by the finding of two skulls at Dmanisi (Gabunia et al., 2000). These hominids possesed the Oldowan (Mode I) Industrial Complex, since the population dispersed out of Africa before the emergence of the Acheulean (Mode II) technological system (i.e., before 1.5-1,4 M.yr.). The first evidence of this faunal dispersal is recorded at the Plio-Pleistocene transition (1.8-1.6 M.yr.) in Western Europe, within the Olivola and Tasso faunal units, and in Central Eurasia (Dmanisi), where exists a complete record of this dispersal event, including human remains and evidence of cultural activity. Southeast Spain (Orce-Cueva Victoria, 1.4-1.1 M.yr.) has an exceptional record of these faunal assemblages, as well as the technological evidence of the first human populations. Finally, the most complete anatomical and cultural evidence of the hominids who could have been the descendant of those directly implied in the first colonization of Eurasia is found at the Gran Dolina of Atapuerca (-0.8 M.yr.). Therefore, the recent fmdings in Atapuerca TD-6 Level do not support the scenario of the mature hypothesis for a colonization of Europe at -1 M.yr., given (i) the anatomical features of the hominid remains, which have been attributed to a new species, H. antecessor (but which are probably better related to H. ergaster); (ii) the lack of fit between the age proposed for the site, its geographic location and the Oldowan/Acheulean chronology; and (iii) the faunal incongruity (i.e., Asian origin of the middle Galerian species preserved in the assemblage). On the contrary, the record from Atapuerca fills in part the palaeoanthropological hiatus of the "old hypothesis" (i.e., the colonization of Europe before 1.5 M.yr. ago). We consider that the hominids from TD-6 could represent one of the latest European populations of the lower Pleistocene, descended from the ancestor lineage defined by H. ergaster, which retained its initial Oldowan technology and survived in Europe after the extinction that affected other species of large mammals in Africa at 1.5 M.yr. Such extinction event changed the composition of the carnivore guild, including the dissapearance of the sabre-toothed cats and the giant hyaenas. Sabre-tooths were the top predators of the palaeocommunity, showing a highly specialised craniodental design and a powerfully built postcranial skeleton (Arribas & Palmqvist, 1998, 1999). These features indicate that they were able to hunt very large prey relative to their own size, and left on the carcasses of their prey large amounts of flesh and all within bone nutrients, which could be subsequently scavenged by other carnivores, such as the bone-cracking hyaenas and the hominids. The loss of these resources seems to have forced the technological evolution to Mode II technologies in Africa (Arribas & Palmqvist, 1999). However, the survival in Europe of hominids with mode I artefacts until 0.5 M.yr. was possible thanks to the meat and bone marrow provided by their ability to scavenge with these technologically primitive tools the carcasses of ungulates hunted and partially defleshed by sabretooths (Homotherium latidens and Megantereon whitei), which inhabited Europe until this age. The extinction in Europe of these predators at -0.5 M.yr. and their substitution by the pantherine cats opened the ecological scenario to the more elaborated, Mode-II tools (Arribas & Palmqvist, 1999). ACKNOWLEDGMENTS.- This research has been financed by a research project from the "Direccirn General de Ensefianza Superior e Investigacirn Cientifica" (DGESIC PB97-1082). Thanks to Rob Walsh for his insightful comments and constructive review of the manuscript.

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Received May 11, 2000

Accepted November 10, 2001