Genetic study suggests that Sima hominins were proto-Neanderthals

430,000-year-old nuclear genome sequences confirms affinities  

Sima de los Huesos (‘Pit of Bones’)is a small muddy chamber lying at the bottom of a 13 m (43 ft.) chimney, lying deep within the Cueva Mayor system of caves in the Sierra de Atapuerca of northern Spain. Hominin remains were first reported there in the 1970s, and to date the remains of 28 individuals have been recovered. The Sima hominins lived around 430,000 years ago and while conventionally described as Homo heidelbergensis, they share some derived features with Neanderthals. This has led some to suggest that they are very early Neanderthals.

In 2014, mitochondrial DNA was obtained from the thighbone of one of the Sima hominins. It was expected that it would show affinities to later sequences obtained from Neanderthals, but instead it suggested that the Sima hominins were more closely related to Denisovans. However, mitochondrial DNA does not reveal the full picture of relationships among populations, so researchers set about the more difficult task of obtaining nuclear sequences from the Sima remains.

Genetic material was recovered from an incisor and a molar tooth, a fragment of a thighbone and a shoulder blade. Useful sequences were obtained from the incisor tooth and the thighbone fragment. The results have shown that the Sima hominins were, after all, more closely related to Neanderthals than they were to Denisovans. The Sima hominins were thus either early Neanderthals or closely related to the ancestors of Neanderthals after diverging from a common ancestor shared with the Denisovans. The age of the Sima remains is compatible with earlier estimates that the Neanderthal/Denisovan split occurred between 381,000 and 473,000 years ago. Based on the correctness of these estimates, modern humans diverged from Neanderthals 550,000 to 765,000 years ago – too early for later examples of Homo heidelbergensis such as Arago or Petralona to belong to a population ancestral to both Neanderthals and modern humans. The true common ancestor may be Homo antecessor, which was present in Spain from 1.2 million to 800,000 years ago and might have been responsible for the hominin footprints discovered at Happisburgh, England, in May 2013. However, this species has yet to be identified in Africa and may be a European variant of Homo erectus that migrated from Asia.

The Denisovan affinities of the mitochondrial DNA are still unexplained. One possibility is that the common ancestor carried mitochondrial lineages present in both, but later eliminated from the Neanderthals. The authors noted that this requires an explanation for the presence of two deeply divergent mtDNA lineages in the same archaic group, one that later recurred in Denisovans but disappeared from the Neanderthals; and one that became fixed in Neanderthals. The required explanation might be later population bottlenecks that are known to have affected Neanderthal populations. However, the authors preferred explanation is that the mitochondrial genomes of later European Neanderthals was acquired by interbreeding with hominins from Africa. This might explain the absence of Neanderthal-derived morphological traits in some European Middle Pleistocene hominins such as Ceprano and Mala Balanica.

Reference:
Meyer, M. et al., Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins. Nature (Published online) (2016).

Killed with a blunt instrument

Evidence for lethal interpersonal violence in the Middle Pleistocene

Evidence of interpersonal violence between humans resulting is (perhaps surprisingly) rare in the Pleistocene. Examples include the Shanidar 3 and St. Césaire 1 Neanderthals, from Iraq and southwestern France respectively. Shanidar 3 suffered a penetrating injury from a projectile weapon, and St. Césaire 1 suffered a fractured skull consistent with a deliberate blow from a sharp object. It cannot be ruled out that the injuries were the result of accidents: a hunting injury in the case of Shanidar 3 and a fall in the case of St. Césaire 1 (though the location of the injury at the apex rather than side of the cranial vault makes this unlikely). Neither incident was fatal, at least not immediately so, as both lived long enough thereafter for healing to begin. There are also cases where bones have been de-fleshed and broken open to extract marrow, suggesting cannibalism – although it is unclear whether individuals were attacked and killed, or whether they were already dead and possibly eaten by their companions.

The 430,000-year-old site of Sima de los Huesos (‘Cave of Bones’) in northern Spain has yielded a large number of human remains described as either Homo heidelbergensis or as proto-Neanderthals. The remains were found in a deep pit into which they were intentionally dropped, either as part of a mortuary ritual or more likely as a means of hygienically disposing of dead bodies.

Cranium 17 is a very complete cranium recovered in 52 pieces. It comprises the entire face, including much of the upper dentition (upper right C to M3 and upper left C to M2), the frontal bone, most of the sphenoid bone, the left parietal bone, the left temporal bone minus the mastoid process, and most of the occipital bone. The slight dental wear suggests that Cranium 17 belonged to a young adult.

Most of the fragmentation of the cranium involved dry bone breakage occurring long after death.

However, there were two unhealed depressed fractures consistent with blunt force trauma from the same weapon (or ‘tool’ as the paper euphemistically describes it), resulting in penetration of the bone-brain barrier. Either injury would probably have been fatal: two suggests an intention to kill. Furthermore, the presence of two injuries caused by impact with the same object more or less rules out post-mortem damage to the cranium caused by it landing on a hard object when it was dropped into the pit, or by subsequent rock-falls.

Cranium 17 represent the earliest reasonably clear-cut case of interpersonal violence between humans leading to death. It demonstrates that this rather depressing aspect of human behaviour has an ancient origin.

References:
Sala, N. et al., Lethal Interpersonal Violence in the Middle Pleistocene. PLoS One (2015).

 

 

530,000 years old Spanish hominins were closely related to Denisovans

Mystery of Sima de los Huesos ‘proto-Neanderthal’ mitochondrial genome.

Sima de los Huesos – ‘the Pit of Bones’ –  is a small muddy chamber lying at the bottom of a 13 m (43 ft.) chimney, lying deep within the Cueva Mayor system of caves in the Sierra de Atapuerca of northern Spain. Human remains dating to the Middle Pleistocene were first discovered there in 1976, and systematic excavation has been in progress since 1984. Investigation of the cramped site has proved to be long and difficult – it is located more than 500 m (⅓ mile) from the mouth of the Cueva Mayor and is hard to access, necessitating at times crawling on the stomach. To date, over 2,000 fragmentary hominin fossils have been recovered, including three skulls. In total, the remains are thought to represent at least 32 individuals of both sexes. Many of the remains are of adolescents and young adults, though, the pattern of mortality was probably quite normal for the time, and a similar peak in adolescence has been found at a site at Krapina in Croatia. There is no evidence for violence and the deaths could simply be the result of hunting accidents and childbirth complications. Hunting accidents were probably not uncommon among inexperienced young hunters and women likely fell pregnant soon after commencing menstruation (Pettitt, 2005).
Uranium-series dating suggests that the remains are least 530,000 years old (Bischoff, et al., 2007), and display a mixture of Homo heidelbergensis and Neanderthal features. For this reason, the  Sima de los Huesos hominins are often described as ‘proto-Neanderthal’ (Klein, 2009), although it has also been argued that they were a species distinct from both Neanderthals and Homo heidelbergensis rather than an intermediate between the two (Tattersall, 2002).

In a newly-published study, researchers at the Max Planck Institute for Evolutionary Anthropology have reported the sequencing of the almost-complete mitochondrial genome of one of the Sima de los Huesos hominins. The mitochondrial DNA was extracted from a thigh bone. An estimated age of 400,000 years was obtained by comparison with other, younger ancient DNA sequences dated by direct means. This is rather more recent than the uranium series dates for the site, but still by far the oldest hominin DNA ever recovered. The previous record-holder was no more than 100,000 years old.

Given the geographical location of the Sima de los Huesos and the apparent affinities of the hominins to Neanderthals, it was expected that the material would show affinity to genetic sequences obtained from later Neanderthal remains. Instead, it more closely resembled ancestral Denisovan mitochondrial DNA (Meyer, et al., 2013).

The Denisovan genome, first identified Denisova Cave in the Altai Mountains of southern Siberia, has been found in the modern populations of New Guinea and Island Southeast Asia, implying that the Denisovan range had once extended from the deciduous forests of Siberia to the tropics. This is a wider ecological and geographic region than any other hominin species, with the exception of modern humans (Reich, et al., 2011); but could their range have extended all the way to Europe?

It is likelier that the Sima de los Huesos hominins were the common ancestors of both the Neanderthals and the Denisovans. Mitochondrial lineages originally present in both lineages subsequently disappeared from the Neanderthals, but persisted in the Denisovans. They could have been lost from the Neanderthal line as a result of a population bottleneck of the type known to have affected later Neanderthal populations (Dalén, et al., 2012).

References:

1. Pettitt, P., in The Human Past, edited by Scarre, C. (Thames & Hudson, London, 2005), pp. 124-173.

2. Bischoff, J. et al., High-resolution U-series dates from the Sima de los Huesos hominids yields 600 +/-66 kyrs: implications for the evolution of the early Neanderthal lineage. Journal of Archaeological Science 34, 763-770 (2007).

3. Klein, R., The Human Career, 3rd ed. (University of Chicago Press, Chicago, IL, 2009).

4. Tattersall, I., in The Speciation of Modern Homo sapiens, edited by Crow, T. (Oxford University Press, Oxford, 2002), pp. 49-59.

5. Meyer, M. et al., A mitochondrial genome sequence of a hominin from Sima de los Huesos. Nature (Published online) (2013).

6. Reich, D. et al., Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania. American Journal of Human Genetics 89, 1-13 (2011).

7. Dalén, L. et al., Partial genetic turnover in neandertals: continuity in the east and population replacement in the west. Molecular Biology and Evolution 29 (8), 1893-1897 (2012).

Projectile weapons invented almost 280,000 years ago, by pre-modern humans

Study suggests Ethiopian Rift stone points were used as hafted javelin tips.

The invention of projectile weaponry was clearly an important advance for early humans, enabling large mammals or enemies to be killed or wounded at a distance, without the dangers of a confrontation at close quarters.

The earliest humans probably hunted to an extent, but unequivocal evidence for the hunting of large mammals does not appear in the archaeological record until the Middle Pleistocene. In 1995, four wooden spears were discovered at an open cast mine near the town of Schöningen in Germany. The 400,000-year-old weapons were found with the carcasses of the horses they had been used to kill: the earliest-known association of hunting weapon with quarry. Each spear was over 2 m (6 ft. 6 in.) long, sharpened at both ends, and scraped smooth with stone tools (Thieme, 1997). However, these were unlikely to have been projectile weapons. They are closer in thickness to ethnographically-recorded thrusting spears rather than throwing spears, and if thrown would have had a killing radius of less than 8 m (26 ft.) (Shea, 2006).

Even earlier are the 500,000-year-old stone points from the site of Kathu Pan 1 (KP 1) in South Africa. Some exhibit fractures to their ends, bases and edges that are consistent with a short-ranged weapon striking a target – but not with use for cutting or scraping. The points are shaped near the base in a way that suggests that they were hafted to wooden spears. Experiments with replicas of the KP 1 points, made from similar raw materials, suggest that they made effective spear tips. This makes them the earliest-known multi-component tools; however, they were thrusting spears rather than projectile weapons (Wilkins, et al., 2012).

Throwing spears or javelins were once thought to be a technology unique to modern humans. However, a newly-published study suggests that they predate the emergence of Homo sapiens by 80,000 years. The Gademotta Formation is an archaeological site located on the flanks of an ancient volcanic caldera in the Ethiopian Rift. Investigations since 2010 have yielded over two hundred intact or fragmentary stone points, nearly all of which made from locally-available obsidian. Obsidian is a naturally-occurring volcanic glass that is well-suited to the production of implements with a sharp cutting edge. Argon-argon dating suggests that the oldest of the artefacts are 279,000 years old. Many of the points were found to bear fracture patterns on their tips consistent with impact damage arising from their use as hafted javelin tips, rather than as thrusting weapons (Sahle, et al., 2013).

The pre-modern humans living in Africa at this time are commonly referred to as Homo heidelbergensis. It is commonly supposed that they lacked the cognitive abilities of modern humans (Klein & Edgar, 2002), but the emerging view is that the sophistication of Middle Pleistocene humans has been severely underestimated. The Gademotta projectile tips are an important piece of evidence in this new picture.

References:

1. Thieme, H., Lower Paleolithic hunting spears from Germany. Nature 385, 807-810 (1997).

2. Shea, J., The origins of lithic projectile point technology: evidence from Africa, the Levant, and Europe. Journal of Archaeological Science 33, 823-846 (2006).

3. Wilkins, J., Schoville, B., Brown, K. & Chazan, M., Evidence for Early Hafted Hunting Technology. Science 338, 942-946 (2012).

4. Sahle, Y. et al., Earliest Stone-Tipped Projectiles from the Ethiopian Rift Date to.279,000 Years Ago. PLoS One 8 (11) (2013).

5. Klein, R. & Edgar, B., The Dawn of Human Culture (John Wiley & Sons, Inc., New York, NY, 2002).

Out of Europe?

Three weeks ago, I criticised the “quality” papers (the “Daily Telegraph” was an exception) for running a story based on a two-year-old paper about Homo georgicus as fresh news and for hyperbolic headlines about “rewriting the history of man”. True to form, the media have now completely missed out on an article published in Nature which does – if its conclusions are correct – have a substantial bearing on how we view the path of human evolution. The paper appeared in the 3 September edition of the journal, but due to a postal service that would be considered a disgrace in Somalia, it has only just reached me.

The paper entitled “The oldest hand-axes” in Europe is by Gary R. Scott and Luis Gibert of the Berkeley Geochronology Center, Berkeley, CA. It reports the re-dating of Acheulean hand-axes from Solana del Zamborino and Estrecho del Quipar, both in south eastern Spain. Both sites were previously considered to be among the younger Acheulean sites on the Iberian Peninsula. An age of approx 200ky assumed for Solana was based on its well-developed Acheulean technology. However Scott & Gibert reported revised dates of 0.9mya and 0.76mya for Solana del Zamborino and Estrecho del Quipar respectively, based on magnetic polarity considerations (Scott & Gilbert, 2009).

The oldest Acheulean hand-axes are around 1.65my old, from West Turkana in Kenya and by 1.4mya their usage was fairly widespread in Africa so on the face of it the fact that hand-axes had reached Spain by 0.9mya is hardly earth-shattering, albeit interesting. However while Acheulean hand-axes were once described as displaying a “variable sameness” that strikes “even enthusiasts as monotonous”, later hand-axes do appear to be more refined than earlier ones, which tend to be much thicker, less extensively trimmed and less symmetrical. The “evolved Mode 2” technology is not seen in the archaeological record in Africa until after 600,000 years ago, 300,000 years after its appearance in Spain.

The significance of this is that while even the earlier hand-axes probably represented a cognitive advance over that required to produce the early Oldowan tools, the later hand-axes possess three-dimensional symmetry that may imply a further cognitive advance as the tool would have had to be viewed and rotated through the mind’s eye while it yet remained a block of un-worked stone (Klein, 2005). The date of 600,000 years ago coincides with the first appearance in the fossil record of Homo heidelbergensis, which while slightly smaller-brained than a modern human, was considerably better endowed in that department than its supposed ancestor, Homo erectus. Homo heidelbergensis (or archaic Homo sapiens as it was known until fairly recently) is believed to be the common ancestor of both modern humans and the Neanderthals. Its bigger brain may have helped it to master the harsh conditions in Europe, which was periodically affected by episodes of glaciation. It could also have been responsible for the refinement in hand-axe making technology.

One problem is that there is no obvious evolutionary cause for this expansion in brain size if we accept, as is generally assumed, that Homo heidelbergensis evolved in Africa. The earliest human species, Homo habilis, possessed a larger brain than the australopithecines it is supposed to have evolved from. Its appearance coincides with the start of the present series of ice ages, 2.6 million years ago. Similarly Homo erectus – which also represented a cognitive step-up from its predecessor – appeared around 1.8-1.7mya during a further deterioration in the climate. But no such event seems to signal the appearance of Homo heidelbergensis.

While it would be a mistake to think there is agreement on the matter, a widely-held view is that Homo heidelbergensis evolved in Africa and migrated into Europe. The European deme eventually became the Neanderthals while the stay-at-home African deme eventually became Homo sapiens. Homo heidelbergensis was not the first human species to colonise Europe, but it was the first to stay there and reach more northerly places such as England and Germany. Previous migrants seem to have eventually been extinguished such as Homo antecessor, known from Level TD6 of the Gran Dolina cave, Atapuerca, Spain or back-migrants from Asia, en route back into Africa such as Homo cepranensis, known from a single skull found near Ceprano, Italy. The technology of the TD6 people was pre-Acheulean, that of the Ceprano people unknown. Both “species” were probably Homo erectus (broadly defined) and they were in Europe at about the same time as the makers of the Solana tools.

If it is the case that a) the re-dating is correct and, b) the “2g Acheulian” Solana tools were beyond the capabilities of Homo erectus then another human species must have made them. One possibility is Homo antecessor, but the problem is that while this species is said to have been larger-brained than “standard” Homo erectus (Bermudez de Castro, Arsuaga, Carbonell, Rosas, Martınez, & Mosquera, 1997) it lacked even the older-style Acheulean tools (Carbonell, et al., 2008), though we cannot rule out the possibility that these might at some stage come to light.

A more radical possibility is that a Homo erectus group equipped with Acheulean technology migrated into Europe and – unlike other migrants – managed to adapt to the harsher conditions. These provided the selective pressure for brain expansion and the migrant population eventually evolved into Homo heidelbergensis which then ranged far and wide throughout Eurasia, eventually evolving into the Neanderthals. But one group moved back into Africa and eventually became Homo sapiens. Thus the immediate ancestors of modern humans were actually a species of European origin rather than African.

© Christopher Seddon 2009
References:
Bermudez de Castro, J., Arsuaga, J., Carbonell, E., Rosas, A., Martınez, I., & Mosquera, M. (1997). A Hominid from the Lower Pleistocene of Atapuerca, Spain: Possible Ancestor to Neandertals and Modern Humans. Science , 276, 1392-1395.
Carbonell, E., Bermudez de Castro, J., Pares, J., Perez-Gonzalez, A., Cuenca-Bescos, G., Olle, A., et al. (2008). The first hominin of Europe. Nature , 452, 465-470.
Klein, R. (2005). Hominin Dispersals in the Old World. In C. Scarre, The Human Past (pp. 84-123).
Scott, G., & Gibert, L. (2009). The oldest hand-axes in Europe. Nature , 461, 82-85.

Homo heidelbergensis

Introduction:
Homo heidelbergensis, or “archaic Homo sapiens”, is the name given to the large-brained hominins that appeared in Africa 600,000 years ago and migrated into Europe and possibly Asia. It is conventionally regarded as having given rise to modern humans in Africa and the Neanderthals in Europe.

The type specimen is the Mauer Mandible (Mauer 1), a virtually-complete lower jaw recovered from fluvial beds near the village of Mauer, in south-west Germany. The find was made on 21 October 1907 by a gravel-pit worker named Daniel Hartmann and described the following year by Professor Otto Schoetensack of the University of Heidelberg. The Mauer Mandible has been dated to 500,000 years old.

Until about ten years ago, the rather unsatisfactory term “archaic Homo sapiens” was used to describe any mid-Pleistocene hominin that wasn’t Homo erectus, Homo sapiens, or a Neanderthal. The latter was usually classified as a subspecies of Homo sapiens, i.e. H. s. neanderthalensis, but they are now generally regarded as a separate species. Consequently “archaic Homo sapiens” is itself regarded as a separate species, with the 1907 name Homo heidelbergensis having seniority under the rules of taxonomy.

As Manzi (2004) notes however this is no more than a revision of the old paradigm, with the substitution of a grade “archaic Homo sapiens” with a clade, Homo heidelbergensis, accompanied by the recognition of three distinct species, i.e. H. heidelbergensis, H. neanderthalensis and H. sapiens, with corresponding speciation events between the Middle and Late Pleistocene in Africa and Eurasia.

Whether or not Homo heidelbergensis is a genuine species or simply a grade of “Version 3.0 human” containing several species remains controversial.

Key Fossils:
Kabwe (Broken Hill), Zambia: Skull and several postcranial bones including a femur and a tibia (Broken Hill 1). It was found in an iron and zinc mine in Broken Hill, Northern Rhodesia (now Kabwe, Zambia) in 1921 by a Swiss miner named Tom Zwiglaar. Dating is uncertain, but probably between 700,000 and 400,000 years old. It has a cranial capacity of around 1100cc and was originally described as Homo rhodesiensis.

Lake Ndutu, Tanzania: a 400,000 year old cranium, found in 1973, with an estimated cranial capacity of 1100cc.

Bodo, Middle Awash, Ethiopia: a 670,000-600,000 year old cranium found in 1976 by a survey headed by Jon Kalb. Cranial capacity is 1300cc.

Sima de los Huesos, Atapuerca, Spain: 350,000 year old remains representing 28 individuals, including three nearly complete skulls, SH4 (cranial capacity 1390cc), SH5 (cranial capacity 1125cc) and SH6 (cranial capacity 1220cc).

Petralona, northern Greece: Skull discovered in cave system in 1960, dated 250,000 – 150,000 years old, with a cranial capacity of 1200cc.

La Caune de Arago, Tautavel in southern France: isolated teeth, cranial, mandibular and fragmentary postcranial remains belonging to at least four adults and three children, dated to approximately 450,000 years old. The distorted Arago 21 cranium has an estimated capacity of 1150cc.

Mauer, Germany: the Mauer Mandible, as mentioned above.

Steinheim, Germany: a distorted but nearly complete cranium found in a gravel pit 1933 by Karl Sigrist. It is believed to be 350,000-250,000 years old. The cranial capacity is 1100cc.

Boxgrove, England: a partial tibia discovered in 1994 dated to 423,000-362,000 years old, associated with Acheulian tools.

Swanscombe, England: three skull fragments belonging to the same individual recovered between 1935 and 1955; believed to be 300,000-200,000 years old and popularly known as Swanscombe Man, though now thought to be female. The cranial capacity has been estimated at 1325cc.

Dali, Shaanxi Province, China: a 250,000 year old cranium discovered by Shuntang Liu in 1978, with a cranial capacity of 1120cc.

Jinniu Shan: cranium, vertebrae, ribs, pelvis, patella and limb bones discovered in 1984. The cranial capacity is 1300cc and the remains are believed to be 250,000 years old.

Description:
Manzi (2004) selects the Middle Pliocene fossils from Kabwe, Petralona and Dali fossils as being typical of Homo heidelbergensis. They have a “transitional aspect” between earlier and more recent hominins which include both primitive and derived traits. Primitive or “archaic” features include a heavily-built cranial structure with massive brow ridges; crests in the temporo-occipital region, including erectus-like occipital and angular tori; a low and antero-posteriorly elongated cranial vault; a protruding and large facial skeleton; and the absence of a modern chin. These traits are however reduced in comparison to Homo ergaster/erectus.

The main derived feature is that the general shape of the cranial vault is consistent with increased brain-size. The frontal is less receding than it is in earlier hominins; the parietal profile is more convex along the mid-sagittal plane and less angled in coronal sections; and the occipital squama is more vertical and arched.

The cranial capacity is typically between 1100-1300cc, around 90% of that of modern humans, a considerable increase on that of Homo erectus/ergaster.

Affinities to other hominins:
The view that this species evolved in Africa about 600,000 years ago, then migrated into Europe, and that the two lineages led to respectively Homo sapiens and the Neanderthals, is probably as convincing as any of the alternatives.

Homo antecessor (known only from Spain) has recently been touted as ancestral to Homo heidelbergensis, suggesting that either the latter was a European species that later migrated back into Africa, or that Homo antecessor evolved in Africa.

Another possibility is that African and European Homo heidelbergensis are different species, with the Bodo Cranium an early example of the former. On this view, the African species would take the name originally assigned to the Bodo Cranium, Homo rhodesiensis. However the sudden increase in brain size to 90% of the modern average seen in the fossil record at around 600,000 years ago, after remaining more or less static at 65% during the previous 1.2 million years, does suggest a punctuated event which in turn suggests a single species.

Just about all that can be safely said at the present time is that our understanding is very incomplete!

Technology:
Homo heidelbergensis is associated with the same Acheulian (Mode II) technology as that originated by Homo ergaster 1.65 million years ago; however later Acheulian hand-axes are thinner, more symmetric and more extensively trimmed. Some authorities describe this technology as “Late Acheulian”. It is possible that its appearance is connected with the emergence of Homo heidelbergensis and is a product of this species greater cognitive abilities.

References:

J. M. Bermudez de Castro, J. L. Arsuaga, E. Carbonell, A. Rosas, I. Martınez, M. Mosquera (1997): A Hominid from the Lower Pleistocene of Atapuerca, Spain: Possible Ancestor to Neandertals and Modern Humans, Science Vol. 276 30 May 1997.

Cameron D & Groves C (2004): Bones, Stones and Molecules: “Out of Africa” and Human Origins, Elsevier Academic Press.

Conroy G (1997): “Reconstructing Human Origins: A Modern Synthesis”, W.W. Norton & Co. Inc, New York, NY & London.

Klein, R. (1999): The Human Career (2nd Edition), University of Chicago Press.

Klein R & Edgar B (2002): “The Dawn of Human Culture”, John Wiley & Sons Inc., New York.

Lewin, R and Foley, R 2004: Principles of Human Evolution (2nd edition), Blackwell Science Ltd.

Manzi G (2004): Human Evolution at the Matuyama-Brunhes
Boundary, Evolutionary Anthropology 13:11–24 (2004).

Scarre C (2005) (Ed): “The human past”, Thames & Hudson.

Stringer C & Andrews P (2005): “The Complete World of Human Evolution”, Thames & Hudson.

© Christopher Seddon 2009

Homo antecessor

Homo antecessor (“Pioneer Man”) is the name given to an extinct human species known from just two sites in the Atapuerca Hills of Northern Spain – Gran Dolina and Sima del Elefante. The remains were discovered by Eudald Carbonell, Juan Luis Arsuaga and J. M. Bermúdez de Castro.

The initial discoveries were made at the Gran Dolina Cave, Layer TD6 between 1994 and 1995. The find comprised over 90 bone fragments including 18 skull fragments, 4 partial jaws, 14 teeth, 16 vertebrae, 16 ribs, 20 bones from the hands and feet, 2 wrist bones, 3 collar bones, 2 lower arm bones, a thigh bone and 2 knee-caps from a minimum of 6 individuals, all of whom were aged between 3 and 18 when they died. Around 200 flaked stone artefacts were also found. Palaeomagnetic considerations date the find to at least 700,000 years old; electron spin resonance dates the fossils and artefacts to between 857,000 and 780,000 years old; bones of extinct rodent species support this age; the excavators conservatively date the find to 800,000 years old.

However in 2007 a fragment of a mandible and an isolated lower left fourth premolar from the same individual were recovered from the TE9 layer at the nearby Sima del Elefante site. These have also been assigned to Homo antecessor and dating based on palaeomagnetism, biostratigraphy and cosmogenic nuclides suggests an age of 1.2–1.1 million years.

The tools found at the Gran Dolina are simple Mode 1 (Oldowan) technology, with no evidence of Acheulian hand-axes or cleavers characteristic of later African Homo ergaster or H. heidelbergensis.

One of the most significant features of the Gran Dolina TD6 find is that around 25% of the bones show signs of human-caused damage including chop and cut marks, peeling where bones have been broken and bent, and percussion marks where bones have been splintered for marrow extraction. All of which adds up to a compelling case for cannibalism. The extent of the damage suggests this was of a dietary rather than ritual nature, suggesting in turn nutritional stress.

Bermúdez de Castro and his colleagues argue against the currently popular view that hominids such as Mauer, Vertesszollos, Bilzingsleben, Arago, and Petralona, together with Bodo, Broken Hill 1, and Dali (among other middle Pleistocene fossils not considered to be H. erectus) belong to a single species, Homo heidelbergensis, that was ancestral to both modern humans and the Neanderthals. They argue that European middle Pleistocene fossils are ancestral only to the Neanderthals and that the Mauer mandible, the holotype for Homo heidelbergensis, shows clear derived Neanderthal traits, such as a large retromolar space, whereas teeth shape and morphology are indistinguishable from those of Neanderthals. They conclude that other than a European chronospecies, H. heidelbergensis should be rejected.

Dental and cranial features suggest Homo antecessor is close to Homo ergaster. While Homo antecessor has similarities to Homo heidelbergensis (i.e. proto-Neanderthals), it has more traits in common with modern humans than does Homo heidelbergensis, being for example relatively gracile, most similar to H. ergaster and modern humans but unlike H. heidelbergensis or the Neanderthals. On this picture, Homo antecessor evolved from Homo ergaster in Africa then spread via the Middle East to Europe where it evolved (via Homo heidelbergensis) into the Neanderthals. In Africa Homo antecessor evolved into Homo sapiens via such fossils as the Bodo and Kabwe skulls. The species Homo rhodesiensis or Homo helmei would have to be revived for these presumptive H. antecessor/H. sapiens transitional types, with H. heidelbergensis being a solely European transitional type between H. antecessor and the Neanderthals.

Neither this view nor Homo antecessor as a species is widely accepted. Many believe that H. antecessor is an ofshoot of Homo ergaster and that it died off without issue, possibly during the glacial periods of 800,000-600,000 years ago. Clearly further evidence is needed, from Africa in particular.

References:

J. M. Bermudez de Castro, J. L. Arsuaga, E. Carbonell, A. Rosas, I. Martınez, M. Mosquera (1997): A Hominid from the Lower Pleistocene of Atapuerca, Spain: Possible Ancestor to Neandertals and Modern Humans, Science Vol. 276 30 May 1997.

Cameron D & Groves C (2004): Bones, Stones and Molecules: “Out of Africa” and Human Origins, Elsevier Academic Press.

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© Christopher Seddon 2008