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Fósiles Humanos - Trinchera Dolina

THE HUMAN FOSSILS FROM GRAN DOLINA TD-6 LEVEL: 'Homo antecessor'

The first Europeans

The origin and antiquity of the first Europeans has inspired an enormous interest in both the scientific community and the general society since the first Neandertal fossils discovered in the 19th Century (from such sites as Engis in Belgium, Forbes Quarry in Gibraltar and the Feldhofer Cave in the Neander Valley in Germany) were correctly interpreted as “primitive humans” from remote populations of humanity. Decades later, we know that the evolutionary history of human populations in Europe has been extraordinarily complex and goes back perhaps more than a million years. Who were these ancestors who first inhabited the European continent? At what point did hominids enter the territory we now know as Europe? How are these original pioneers related to current European populations? Why did hominids expand their territory and move out of Africa to occupy new environments?

Each new discovery at sites in Europe, Africa and Asia, as well as advances in other disciplines related to the study of human origins, have allowed scientists to answer these questions in their attempt to reconstruct the geographic and temporal patterns of human evolution in Europe. Where are we in these studies today? What have the discoveries and the results produced by the research team during more than 30 years of excavations at the sites in the Sierra de Atapuerca contributed to these questions?

At the beginning of the 1990's a large majority of prehistorians defended the idea that the first colonization of Europe had occurred around 500,000 years ago. The well-known Mauer mandible, which was discovered in 1907 near Heidelberg in Germany, was the first representative of the newly created species dubbed Homo heidelbergensis, and for 90 years, was considered the oldest human fossil in Europe. To this, were added later discoveries from sites in Germany (Steinheim, Bilzingsleben), France (Montmaurin, Arago), Greece (Petralona), the U.K. (Boxgrove, Swanscombe, Pontnewydd) and Spain (Sima de los Huesos in Atapuerca), among others. The study of the fossil remains from this last site has had an enormous impact on the interpretation of the peopling of Europe during the Middle Pleistocene, some 780,000-120,000 years ago.

This complex of European sites, and many others which haven’t yielded human fossils but do preserve clear evidence of different daily activities (e.g. knapping of stone tools, defleshing of animals, curing of animal skins, etc.) offer a vision of Europe inhabited by a relatively homogeneous population of hunters and gatherers, which are collectively classified within the species 'Homo heidelbergensis'. Based on the sites of Notarchirico (Italy) and Carrière Carpentier (France), members of this species occupied Europe beginning some 600,000 years ago using a stone tool technology known as Mode 2, or Acheulean, and eventually controlled fire. But were these populations of 'Homo heidelbergensis' the first people to occupy Europe?

Since the 1980's, the idea that the first inhabitants of Europe could have arrived around one million years ago was being increasingly advocated by part of the scientific community. The supposed evidence came from sites such as Isernia la Pineta, Monte Poggiolo and Notarchirico (all in Italy), Kärlich (Germany), Korolevo (Ukraine) and the lower levels at Gran Dolina in the Sierra de Atapuerca, which all preserved evidence of more primitive stone tools, known as Mode 1, or Oldowan. Ages for these sites derived from direct dating methods, such as potassium-argon (K/Ar) or thermoluminescence (TL), or indirect methods, such as paleomagnetism or biochronology) ranged between 600,000 and one million years ago.

The debate between the defenders and the detractors of a European settlement older than 500,000 years ago centered on the possibility that the stone tools found at these sites were merely naturally fractured rocks, known as geofacts, and did not constitute intentionally manufactured stone tools. Further, most of these Mode 1 tool kits, sometimes associated with fossilized remains of different animal species, were found at sites formed near the banks of lakes and rivers, having been displaced from where they originally accumulated. Thus, they didn’t seem to be in a primary context, and the possibility of water transport could be argued to explain some of the fracture patterns. These reasonable doubts in the interpretation and dating of these sites weakened the argument for a Europe occupied in such remote times.

Aspecto del yacimiento de Trinchera Dolina durante las primeras campañas de excavación Finally, in 1994, excavations at the site of Gran Dolina in the Sierra settled the debate once and for all. In 1993, the Atapuerca research team began a test pit of some six square meters in the site of Gran Dolina with two goals in mind. In the first place, it was necessary to get a better understanding of the stratigraphy as well as the fossiliferous and archaeological potential of the site. Secondly, reaching the lowest, and hence oldest, levels of the site as quickly as possible could provide new data in the debate on the first Europeans. The defenders of the so-called “short chronology” had reinforced their position with the discovery of a tibia fragment of 'Homo heidelbergensis' associated with a rich Mode 2 stone tool assemblage at the site of Boxgrove, in England. The age of this fossil was similar to that of the Mauer mandible. However, levels TD4-TD6 at Gran Dolina were older than 500,000 years, and stone tools belonging to a Mode 1 technology had already been recovered.

In July of 1994, the test pit in Gran Dolina reached level TD6, and a remarkable discovery was made. On the 8th day of the month, several human remains appeared associated with Mode 1 stone tools as well as clearly ancient micromammal and faunal remains. This assemblage appeared together in a level some 25 centimeters thick, which is now known as the Aurora stratum. During three field seasons (1994-1996), these six square meters were meticulously excavated, eventually yielding 85 fragmentary human remains from different parts of the skeleton and representing at least six different individuals. These were associated with 268 stone tools, and more than 4,000 fragmentary fossils of large mammals.

Atapuerca foto. Los tres primeros dientes humanos recuperados en TD-6 (Gran Dolina) en el año 1994 A rigorous taphonomic analysis of the Aurora stratum has demonstrated that the site is in primary context and that the archaeological and paleontological remains are anthropic in origin. That is, the actions of human beings were responsible for producing this accumulation of artifacts, probably in what was an ancient occupation site or campground near the entrance of the large cave that was the Gran Dolina at that time.

The analysis of the “fossilized” magnetic properties of the sediments in the different levels of Gran Dolina has revealed that the lower levels (TD2-TD6 and the lower part of TD7) were deposited during the so-called Matuyama epoch, when the Earth’s magnetic pole was reversed with respect to the present-day. The Matuyama period covers the time range from 1,770,000-780,000 years ago, with a short period of normal magnetic polarity between 1,070,000-990,000 years ago, called the Jaramillo event. ESR and Uranium series dates for level TD6, as well as the studies of microvertebrates and large mammals from the different levels in Gran Dolina, place the human fossils from the Aurora stratum between 780,000-850,000 years ago. Thus, the presence of hominids in Europe beyond the 500,000-year limit of the “short chronology” was definitively demonstrated. The discovery in 1990 of various quartzite stone tools in level TD4, as well as a few flint flakes, and finally in 2007, human fossil remains in the lower levels of the Sima del Elefante, indicate that the earliest occupation occurred in the Sierra at least a million years ago, during the Lower Pleistocene (1,770,000-780,000 years ago).

Atapuerca foto Javier Trueba. Detalle del sondeo de seis metros cuadrados iniciado en el año 1993 en el yacimiento de Trinchera Dolina In 1991, a surprising discovery was made at the site of Dmanisi, located in the Republic of Georgia, between the Caspian Sea and the Black Sea, not far from the Caucasus and at the gates of Europe. A hominid mandible showing very primitive characteristics was found associated with a rich assemblage of Mode 1 stone tools, microvertebrates and large mammal remains. The age of this mandible was determined by paleomagnetic and biochronological data to be at least 1,750,000 years old. The morphology and dimensions of the Dmanisi mandible indicated similarities to the African species 'Homo ergaster' and 'Homo habilis'. While the first publications on the site generated controversy due to the unexpected nature of the find, the recent excavations have offered even more spectacular results.

Three nearly complete crania and two new mandibles have been recovered, as well as some bones of the postcranial skeleton. The study of these fossils has confirmed the similarities of the Dmanisi hominids with 'Homo ergaster,' but has also revealed some distinct characteristics in this population which is separated by thousands of kilometers from the African hominids. Further, the cranial capacities, or brain size, of the three skulls are very small and similar to the values recorded for Homo habilis. The smallest skull (D2700) has a brain size of about 600 cm3, while the other two skulls, D2282 and D2280, have brain sizes of 650 and 770 cm3, respectively. The Dmanisi hominids have been included by their discoverers in a new species, 'Homo georgicus', a probable descendant of 'Homo habilis'. This implies that a form of hominid, with characteristics intermediate between 'Homo habilis' and 'Homo ergaster', left Africa and began the first expansion into Eurasia at the end of the Pliocene, much earlier than we would have believed only a decade ago.

It’s still unclear whether this first dispersal was definitive. Was this an initial, short-term excursion from Africa only followed by a much greater exodus several hundred thousand years later? Alternatively, did the Dmanisi hominids extend their range through the south of Asia, reaching as far as the Indonesian archipelago, and give rise to the species known as 'Homo erectus'? If so, did this first hominid dispersal also lead to the colonization of Europe, which must have occurred much earlier than even the Atapuerca discoveries? But before we go further, let’s take a look at the hominids from TD6. Who were these people, and what role do they play in human evolution?

The human fossils from TD6

Una visión general a muchos de los fósiles de 'Homo antecessor' que han aparecido en el nivel TD-6 de la Gran Dolina The human fossil remains from the Aurora stratum in TD6 correspond to different skeletal parts from a minimum of six individuals. This assemblage includes fragments of the maxilla (upper jaw) and the mandible (lower jaw) as well as parts of the temporal, frontal, occipital, zygomatic, and sphenoid bones. Among the postcranial elements, portions of the clavicle, radius, femur, ribs, vertebrae, patella, and various foot and hand elements (such as metacarpals, metatarsals, hamates and 16 phalanges) are preserved. The maxillary and mandibular fragments, as well as the 30 deciduous (milk) and permanent teeth which form part of the sample indicate that the fossils correspond to two children who died between 3 and 4 years of age (Hominids 2 and 6), two adolescents, one of them between 10-12 years old (Hominid 3) and the other between 13-14 years old (Hominid 1), and two adults who died around 20 years of age (Hominids 4 and 5).

Below, it is listed the remains that belong to each of these individuals. Hominid 1 is well represented by a mandibular fragment, with three molars still in their tooth sockets, and a small fragment of maxilla with the canine and first premolar still in their sockets as well as several more loose teeth. Hominid 2 is recognized by the left portion of a maxilla with the deciduous canine and first deciduous molar in their sockets, as well as the still-forming toothbuds of the permanent incisors, canine and first premolar. Hominid 3 comprises a fragment of the frontal (forehead) bone, which preserves most of the right side and part of the left, as well as a large part of the facial skeleton, including the maxilla and zygomatic (cheek) bone. Several permanent teeth are still in their sockets within the maxilla, some of which are still erupting (the canine, second premolar and second molar) or in the process of crown formation (third molar).

Canino humano de la especie 'Homo antecessor', procedente de la Gran Dolina The TD6 human teeth are larger and more complex than those of living humans. The upper lateral incisor presents a “shovel-shaped” morphology, with thickened crests along the margins of the tooth, somewhat different from that which is still preserved in some recent populations. The premolars and molars have extra cusps and numerous enamel crenulations (“wrinkles”) on the chewing surface. The lower premolars have more than one root, well-developed talonids on the chewing surface and enamel folds on the buccal (cheek) surface. Finally, the size proportions of the tooth crowns, whether comparing within the same class of tooth (premolars or molars) or whether comparing between classes (incisors vs. molars) are very different from modern populations. The TD6 teeth clearly show a “primitive” pattern shared with other species of Homo: 'Homo habilis', 'Homo ergaster' and 'Homo erectus'.

In contrast to the primitive pattern seen in the teeth, the face of Hominid 3, represented by the adolescent maxilla numbered ATD6-69, shows an identical morphology to that seen in modern humans, like ourselves. In the midface, living humans show a distinctive anatomy, which until the discovery of ATD6-69, was believed to be unique to our species, Homo sapiens. An important component of this midfacial anatomy are the infraorbital plates, located to the side of the nose and below the eyes, which are formed by the maxillary and zygomatic bones and whose suture (the line of fusion between the two bones) crosses it diagonally.

In 'Homo sapiens', these infraorbital plates face toward the front. However, they don’t look completely forward, but rather forward and somewhat downward as well. Because of this orientation, the maxilla has a depressed area on its surface, which corresponds to an anatomical structure known as the canine fossa, although this term is somewhat imprecise and has been used in different ways. In addition, in 'Homo sapiens', the bony margins of the nasal cavity are placed further forward than the rest of the face, which produces a certain “prognathism” or projection of the midface, known as midfacial prognathism. We could say that the walls of the nasal cavity run in a parasagittal plane, that is, parallel to the sagittal plane or midline of the body, while the infraorbital plates face forward but are located behind the borders of the nasal cavity. In an idealized representation of the modern human midface, the infraorbital plates and the walls of the nasal cavity join in a right angle, but in reality there is a smoother transition between the two surfaces. This is the morphological pattern which characterizes ATD6-69.

El Chico de la Gran Dolina, de unos 11 años de edad, es el fósil más emblemático de 'Homo antecessor' de Atapuerca The fossil numbered ATD6-58, which consists of part of the left maxilla and malar (cheek) bone, provides information on the midfacial anatomy of the adult specimens of 'Homo antecessor'. This fossil also shows the presence of a canine fossa, but less pronounced than that in ATD6-69. This leads us to believe that in adult members of the TD6 population the face was larger and more inflated than in the juveniles, due to the expansion of the maxillary sinuses during adolescence. The reduction of the facial skeleton in adults is characteristic of 'Homo sapiens' and corresponds to a weaker development of the chewing muscles. As a consequence, the face in our species is more similar to the immature individuals of the species represented in TD6. As we will see, the midface of immature individuals of other Pleistocene human species doesn’t present this modern morphology. In 'Australopithecus' and 'Paranthropus', the infraorbital plates also face forward, but they are oriented either vertically or even face slightly upwards. Further, the margins of the nasal cavity are not placed further forward than the infraorbital plates, and in Paranthropus the margins are even placed slightly behind the cheek bones, making the entire face appear somewhat concave.

The flattened nasal bones, located between the eyes and forming the upper margin of the bony nasal cavity, do not stand out from the rest of the face in profile. Nor do they form an osseous bridge. This morphology is also encountered in fossils of the genus 'Homo' attributed to 'Homo habilis' and 'Homo rudolfensis', as well as in the Dmanisi skulls. This situation changes somewhat in 'Homo ergaster', where the nasal cavity develops more anteriorly, pushing the bony margins forward with respect to the midfacial region (the infraorbital plates). Related to this anterior expansion of the nasal chamber in 'Homo ergaster', the nasal bones are oriented more horizontally in profile view than in the previously mentioned species and form an osseous bridge making up the roof of the nasal cavity. This morphology can be easily seen in some African fossils such as the adult individual KNM-ER 3733 (Kenya), as well as in the juvenile KNM-WT 15,000 (Kenya) specimen, the so-called Turkana boy. This latter fossil provides us with an excellent comparison for the adolescent Hominid 3 from Gran Dolina because both of these immature individuals were at similar growth stages when they died. In spite of these changes just described, the facial architecture in the earliest humans presents little relief compared with our own species. That is, the lack of a forwardly placed nasal chamber, forming a markedly positive relief, and excavated infraorbital plates in the region of the canine fossa, give it an “unsculpted” appearance.

We’re not sure what this region looked like in 'Homo erectus' because there are very few skulls which preserve the face, and even these have led to different interpretations. The most complete specimen is Sangiran 17, from the island of Java in Southeast Asia, which, although deformed, looks like a more robust (heavily built) version of the 'Homo ergaster' face. We should point out here that the cranium of 'Homo erectus' is also a robust version, with a few minor differences, of that of 'Homo ergaster'. It doesn’t seem, therefore, that the facial anatomy in 'Homo erectus' was like our own, nor like that of ATD6-69, but rather represents the evolutionarily primitive state. If this is true, the species represented by the Gran Dolina fossils couldn’t be the ancestor of 'Homo erectus'. This is our current hypothesis, although, of course, we need more fossils to be completely certain.

Cráneo neandertal, con un esquema de su morfología facial especializada (derecha) comparada con la de un hipotético antecesor (izquierda) The Neandertals, on the other hand, present a midfacial anatomy completely different from both the primitive condition seen in Homo erectus and that of our own species. In these fossils, the nasal cavity projects even further forward than in 'Homo sapiens'. Consequently, the nasal bones are oriented completely horizontal, and the walls of the nasal cavity flow smoothly into the infraorbital plate, forming a single surface and giving the midface a more pointed appearance. In this midfacial morphology, the canine fossa is absent, and the cheeks are not pronounced. We believe that the Neandertal midface evolved from the condition seen in ATD6-69, which is also our own, and, in terms of this anatomical characteristic, the Neandertals are evolutionarily more specialized (or “derived”) than ourselves.

European Middle Pleistocene fossils such as Arago 21, Petralona, Steinheim or those from the Sima de los Huesos in the Sierra de Atapuerca show an intermediate stage. In the evolutionary line which gave rise to ourselves, a modern midfacial morphology can be seen in fossils from the sites of Skhul and Qafzeh (both in Israel) at the beginning of the Upper Pleistocene, and in other African fossils which may be even older, such as Jebel Irhoud 1 (Morocco), Laetoli 18 (Tanzania), Broken Hill 2 (Zambia) and Florisbad (South Africa), as well as in the Chinese skull from the site of Dali. Other African fossils, in particular the skulls from Bodo (Ethiopia) and Broken Hill 1, don’t show a modern midface, but neither are they like the Neandertals nor the earliest humans. Our interpretation of these individuals is that the expansion of the maxillary sinuses in these adult faces has disfigured the more modern-looking immature characteristics. Thus, the Bodo specimen presents the peculiar condition of having a very large facial skeleton which is also very inflated.

El Cráneo 5 de la Sima de los Huesos (Burgos, Atapuerca) es el mejor conservado de todo el registro fósil. Se asigna a la especie 'Homo heidelbergensis' Some researchers have also emphasized the importance of the lower borders of the infraorbital plates. They point out that in Asian 'Homo erectus' fossils, this border, technically known as the zygomatic crest, is horizontal and its most medial part (that closest to the midline of the body) is located somewhat above the alveolar margin (the level of the too throw). This morphology is also that seen in our own species, which could lead us to believe there is a certain evolutionary continuity between 'Homo erectus' and 'Homo sapiens'. On the other hand, the lower border of the infraorbital plates in the Neandertals is not horizontal, but runs diagonally, with its most medial part almost joining the alveolar margin, or tooth row. Nevertheless, in the fossils mentioned previously from Gran Dolina, as well as in a third fragment numbered ATD6-19 (a small fragment of the right infraorbital plate), the zygomatic crest is horizontal and the most medial part is located above the alveolar margin. This indicates that the morphology seen in 'Homo antecessor' represents the evolutionarily primitive state, while that of the Neandertals is a derived condition.

The fragments of temporal bone recovered from TD6 preserve two characteristics which also provide information on the evolutionary relationships of 'Homo antecessor' with other Pleistocene species of 'Homo'. The TD6 fossils show the presence of a styloid process, a long, thin bony projection emerging from the base of the skull which serves as an attachment site for several neck muscles. This is a primitive characteristic, which is also present in most skulls that belong to the genus Homo. However, in 'Homo erectus', the styloid process is not fused to the base of the skull, and this species shows a derived condition for this trait. Further, the upper margin of the temporal squama (the flattened portion forming part of the side of the skull) is high and arched, like other Middle Pleistocene fossils from Africa and Europe, as well as in the Neandertals and ourselves. 'Homo erectus', 'Homo ergaster' and 'Homo habilis', on the other hand, have a low and relatively straight upper margin to their temporal squama. The expression of this characteristic in 'Homo antecessor' underlines its close evolutionary relationship with the Neandertals, modern humans and their respective Middle Pleistocene precursors.

De donde venimos: la filogenia de los hominidos This combination of traits in the cranial and dental remains, together with a number of generalized characteristics in the mandibular fragment ATD6-5 which are common to all Lower and Middle Pleistocene hominids from Africa and Europe, led us to propose a new species of the genus Homo, defined by the TD6 fossils: 'Homo antecessor'. In Latin, the name “antecessor” means explorer, or pioneer, and we wanted to suggest that the TD6 hominids belong to a species which colonized Europe during the Lower Pleistocene, much earlier than the emergence of populations represented by fossils such as the Mauer mandible, the Boxgrove tibia or the Sima de los Huesos at Atapuerca. But what was the origin and destiny of "Homo antecessor"? What role did this species play in human evolution?

The primitive pattern of its teeth and the generalized morphology of the mandible of 'Homo antecessor' don’t help much in placing this species within the human evolutionary tree. Some of the dental and mandibular characteristics suggest that Homo antecessor is related to 'Homo ergaster', a Lower Pleistocene species from Africa, whose most complete representatives date to between 1.7-1.5 million years ago. Nevertheless, the new evidence from Dmanisi forces us to reopen the debate on the first Europeans. There is no evidence that the population represented by the hominids from this Georgian site expanded into Europe, and they may never have done so. Even if 'Homo georgicus' did occupy Europe during the Lower Pleistocene, there wouldn’t necessarily have to be an ancestor-descendant relationship with 'Homo antecessor'. The comparisons made to date between the two species, although quite preliminary, indicate some clear differences. As mentioned previously, it’s also possible that the Dmanisi hominids spread out through southern Asia, reaching the island of Java in the extreme southeast and giving rise to the species 'Homo erectus'.

Development and Body Proportions of 'Homo antecessor'

The completely modern anatomy of ATD6-69 suggests a close evolutionary relationship between 'Homo antecessor' and our own species. Although ATD6-69 belongs to an immature individual and the adult facial anatomy of 'Homo antecessor' wasn’t exactly the same as in the adults of our species, we now know that the modern human face appeared through a process called neoteny. This occurs when the adults of a certain species, in this case 'Homo sapiens', retain anatomical aspects characteristic of juvenile individuals. This evolutionary process is usually brought about through what is known as heterochrony, a change in the rate and timing of the somatic (body) development between ancestors and their descendants. This is how adults of 'Homo sapiens' have retained the juvenile aspect of the face from our ancestor species.

La arcada dental del Chico de la Gran Dolina. El estado de emergencia de sus dientes indica que su edad al morir estaría en torno a los 11 años On the other hand, our studies of Hominids 1, 2 and 3, have revealed that the pattern of dental development in the TD6 hominids, which is a reliable indicator of somatic development, is identical to that of modern populations. The dental development pattern is defined by the formation times of the crowns and roots of all the teeth and by the sequence of different important moments in tooth formation. These moments refer primarily to the beginning and end of the crown and root formation of each tooth, which have a particular timing in every species. Hominids 1, 2 and 3 from TD6 preserve teeth which are at different stages in their formation and eruption, and which has allowed us to pinpoint this timing in several teeth at the moment of their death.

The pattern of dental development has a very strong genetic component and is only slightly influenced by external factors in the environment. Further, the pattern of dental development preserves a strict correlation with different aspects of what is known as the “life history pattern” of a species. Among these aspects, the different stages which define the general somatic development of a species deserve special attention. In chimpanzees and gorillas, somatic development occurs during the first 11-12 years of life. During this time, these species experience a long period of infancy, which corresponds with breastfeeding, followed by a long juvenile period, which ends when the animal reaches sexual maturity. So far, all the available evidence indicates that species of 'Australopithecus', 'Paranthropus' and the earliest members of the genus 'Homo' had a pattern of dental development that was similar in many aspects to chimpanzees and gorillas. Thus, these hominids could have had a developmental model similar to these primates, with long infant and juvenile periods, and no more than 11 years of somatic development before reaching sexual maturity. 'Homo antecessor' represents the oldest hominid species in which a completely modern human dental development pattern has been described. This suggests that the two new stages in somatic development which characterize our species were also present in 'Homo antecessor': childhood and adolescence. Further, the duration of somatic development in this species would also have been prolonged, as in 'Homo sapiens', perhaps approximating the 18 years which it currently takes humans to reach the adult stage.

Brain size also maintains a very high correlation with the duration of somatic development. Theoretical analyses suggest that hominids reached a rate of development similar in duration to our own species when they crossed the 1000 cm3 threshold of cranial capacity. In the TD6 hominids, we can only approximate the cranial capacity based on the partial frontal bone ATD6-15. The dimensions (minimum frontal breadth and bistephanic breadth) are larger than in the skulls of 'Homo ergaster' and suggest a cranial capacity greater than 1000 cm3. Although this data is not definitive, it supports the conclusions reached from the study of dental development.

Una visión general a muchos de los fósiles de 'Homo antecessor' que han aparecido en el nivel TD-6 de la Gran Dolina The study of the different bones of the postcranial skeleton, that is, everything else but the cranium, is hampered by the fact that most of them are very incomplete. The most informative remains are an adult clavicle (ATD6-50), an adult radius (ATD6-43), two patellae (kneecaps), probably representing the same individual, as well as the different hand and foot elements. The anatomy of all these fossils, despite showing some primitive characteristics typical of the genus 'Homo' (with the exception of 'Homo habilis'), seems to be very close to that of modern populations. The radius and the clavicle are both long, and the stature estimates based on these bones, using mathematical formulas based on modern humans, suggest the TD6 hominids were around 1.7 meters tall (about 5' 10"), a result which is consistent with the length of the metatarsal. The relatively long radius suggests a high value for the brachial index, a measure of the proportions of the humerus to the radius. This means that, for its stature, 'Homo antecessor' would have had upper limb proportions similar to modern populations.

Cannibalism in the Gran Dolina

In previous paragraphs, we have referred to the fragmentary nature of the TD6 human remains. The same could be said of the fossilized remains of the different large mammal species recovered from this level. Both the human and animal remains appear randomly dispersed throughout the six square meters excavated and the 25 cm in depth of the Aurora stratum. All the remains show a similar fracture pattern, which includes small percussion pits accompanied by striations and abrasions produced by the impact of hard objects. Wider and longer chopmarks, with a V-shaped profile, produced by a hard cutting edge used to cut tendons and dismember bones, as well as splintering typically produced by breaking the shafts of the smaller-diameter long bones, such as the radius and ulna, are also present throughout the assemblage. Numerous cutmarks and scraping marks can also be seen, produced by the sharp cutting edge of different stone tools when cutting tendons and flesh or when removing the periosteum and muscles from the bones. This evidence clearly suggests that the animal and human cadavers were subjected to the same processes of dismemberment, removal of the muscles, evisceration, and extraction of the periosteum and marrow from the bones. The carrying out of this procedure, with nothing more than the hands and a few stone tools, unquestionably implies the consumption of the soft tissues by other human beings.

Canibalismo en el nivel 6 del yacimiento de la Gran Dolina (Atapuerca, Burgos), hace algo más de 780.000 años Among the varied forms of cannibalism on record, we can discard those which occurred in historic times (in the context of magic rituals, funeral ceremonies or clearly pathological cases) involving symbolic thought and a cultural background characteristic of modern populations. It seems more appropriate to consider reasons more in keeping with not only the kind of humanity which existed at the end of the Lower Pleistocene, but also the direct evidence from the TD6 assemblage. The Aurora stratum was deposited during a time of very favorable climatic conditions, according to both the pollen analysis and the composition of the large mammal remains recovered. The abundance and diversity of the species represented, would argue against the hypothesis that the hominids of TD6 were suffering from a severe resource shortage or famine, during which they would have been forced to consume other group members or loved ones to survive, known as survival cannibalism. The hypothesis which best fits the evidence, regardless of whether the archaeological and paleontological record from TD6 represents a very short, concrete moment in time or a longer period of occupation, is that the humans and other animals were consumed as a result of a planned and habitual behavioral strategy. We can’t discard the possibility that the humans were found lifeless and brought back to camp to be consumed. In any case, this type of cannibalism is known as gastronomic cannibalism, in which human beings could form part of the diet under certain circumstances.

The human fossils from level TD6
Inventory of the maxillary, mandibular and dental remains from the Aurora Stratum (TD6 Gran Dolina) representing at least six individuals of 'Homo antecessor'.

ATD6-5: Right mandibular fragment w/(M1-M3)
ATD6-13: Left maxillary fragment w/(C-P3)
ATD6-1: Lower left canine (C)
ATD6-2: Lower left lateral incisor (I2)
ATD6-3: Lower right first premolar (P3)
ATD6-4: Lower right second premolar (P4): H1
ATD6-6: Fragment of lower canine (C)
ATD6-7: Upper right first premolar (P3)
ATD6-8: Upper right second premolar (P4)
ATD6-9: Upper left second premolar (P4)
ATD6-10: Upper right first molar (M1)
ATD6-11: Upper left first molar (M1)
ATD6-12: Upper right second molar (M2)
ATD6-14: Left maxillary fragment w/(dc-dm1): H2
ATD6-15: Frontal bone fragment
ATD6-69: Left maxilla and zygomatic bone w/ Left P3, M1, M2 (unerupted) and M3 (toothbud) and Right I2-M1: H3
ATD6-48: Lower left lateral incisor (I2): H4
ATD6-52: Lower left central incisor (I1): H5
ATD6-312: Upper left lateral incisor toothbud (I2): H6

Abbreviations: I = Incisive; C = Canine; P = Premolar; M = Molar; Mx = Maxillary teeth; Md = Mandibular teeth; d = deciduous teeth [canine (c) molar (m)]; H = Hominid (Number of dental individual)

Lifeways

'Homotherium latidens', un tigre de dientes de sable,  fue uno de los grandes depredadores del Pleistoceno Inferior y Medio de Atapuerca The humans that lived at the Gran Dolina some 800,000 years ago (level TD6) hunted and scavenged in the Sierra, sometimes transporting complete limbs of their prey back to the cave to consume them at leisure. Other times, they took advantage of the cadavers of the bodies they found on the landscape. They particularly liked young horses and deer, which were consumed frequently. For both hunting as well as flesh removal, they used stone tools made on local raw materials, particularly the large cobblestones from the Arlanzón River which made good hammerstones for flintknapping or breaking bones. These humans had already been living in Europe for some time, probably covering large territories in their movements throughout the year, following the migrating animal herds as well as the seasonally available fruits in different regions.

Some 300,000 years ago things had changed. The Gran Dolina is where they had their campsite. The cave had a large entrance with good lighting and the site was probably spacious and comfortable. They seem to have spent a good deal of time there since cut-marked bones are abundant and many of them were smashed to smithereens to extract the marrow. The density of the tools suggests an intensive occupation of the site. After such a long time, the details of how the cave was used by humans are difficult to establish with certainty. We don’t know if they were permanent occupants of the cave, although this is unlikely. Studies of modern populations with a similar lifestyle as the Paleolithic suggest that human groups tend to migrate across a wide territory throughout the year. These groups would change location seasonally in search of forests with abundant ripe fruits, rivers for fishing or migrating herds of animals. The Sierra must have been a good place to spend part of the year.

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