Earliest hominin cancer

Malignant tumour found in 1.7m year old metatarsal
 
Cancer is the primary cause of death in industrialised countries and the second most common cause of death in the developing world. The condition not known to occur in non-chordates and is largely confined to the higher vertebrates. It is extremely ancient, with purported cases of neoplasm found in fossil fish from the Upper Devonian. It may therefore be assumed that hominins have always been afflicted by cancer, but evidence for malignant tumours is rare in the fossil record. The earliest example affecting an archaic human is a case of fibrous dysplasia from a Neanderthal rib dated to 120,000 years ago from the site of Krapina in northern Croatia.

The earliest evidence yet described for malignant bony tumours in the hominin fossil record has recently been announced by a South African team. They found definite evidence for a malignant tumour in a hominin fossil designated SK 7923: a left fifth metatarsal from the cave site of Swartkrans in the Cradle of Humankind, South Africa, dating to between 1.6 and 1.8 million years old. The exact species has not been determined, but the site has previously yielded fossils of Paranthropus robustus and Homo erectus.

The tumour was identified as an osteosarcoma, a rare primary bone cancer which in modern humans usually affects younger people. Early diagnosis and treatment can effect survival rates of 60 to 80 percent, although until the 1960s the outlook was very poor. It was not clear how old SK 7923 was at death, or whether the cancer was the cause of death, but the cancer would have affected their ability to walk and run – which by itself could have ultimately proved fatal.

The same team also reported a benign bone tumour affecting the juvenile Australopithecus sediba MH 1 from Malapa, dating to 1.98 million years ago.

It is often assumed that both malignant and benign tumours in humans are the result of modern lifestyles and environments, but these results show that they occurred in our ancient relatives millions of years before modern industrial societies arose.

References:
Odes, E. et al., Earliest hominin cancer: 1.7-million-yearold osteosarcoma from Swartkrans Cave, South Africa. South African Journal of Science 112 (7/8) (2016).
Randolph-Quinney, P. et al., Osteogenic tumour in Australopithecus sediba: Earliest hominin evidence for neoplastic disease. South African Journal of Science 112(7/8) (2016).x

 

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Flores ‘hobbits’ were already small 700,000 years ago

Earliest Homo floresiensis fossils found at Mata Menge
 
The diminutive Homo floresiensis hominins, popularly referred to as the Flores hobbits, are thought to be descended from normally-sized hominins who underwent a phenomenon known as ‘insular dwarfism’ after they reached Flores. Food shortages combined with an absence of dangerous predators meant that smaller individuals, with lower calorific requirements, were at an advantage and over many generations the entire population ‘downsized’.

Up until now, the evidence for when this process begun have been tentative. The hominins originally found at the western Flores cave site at Liang Bua, though older than once thought, are still no more than 100,000 years old. It has been suggested that stone tools from the sites of Mata Menge and Wolo Sege in central Flores show technological continuity with artefacts associated with the original Homo floresiensis finds at limestone cave of Liang Bua in western Flores. The Mata Menge artefacts are 880,000 years old and those from Wolo Sege are at least at least a million years old, suggesting that hominins were on Flores by then, although these artefacts cannot tell us anything about the size of their makers (Brumm, et al., 2006; Brumm, et al., 2010)

However, Mata Menge has now yielded actual hominin remains, which have been dated to 700,000 years ago by argon-argon and fission track methods. (Brumm, et al., 2016) They comprise an adult hominin fragmentary lower jawbone and six teeth. The fossils have been described as ‘Homo floresiensis-like’ and the jawbone and a molar teeth are even smaller than those of their Liang Bua counterparts. Thus Flores hominins were already downsized by this time. (Van den Bergh, et al., 2016) 

References
:
Brumm, A. et al., Age and context of the oldest known hominin fossils from Flores. Nature 534, 249-254 (2016).
Van den Bergh, G. et al., Homo floresiensis-like fossils from the early Middle Pleistocene of Flores. Nature 534, 245-248 (2016).
Brumm, A. et al., Early stone technology on Flores and its implications for Homo floresiensis. Nature441, 624-628 (2006).
Brumm, A. et al., Hominins on Flores, Indonesia, by one million years ago. Nature 464, 748-753 (2010).

Milner Hall yields first hominin fossils

Fossils recovered at ‘Cradle of Humankind’ site

Sterkfontein is a set of limestone caves near Krugersdorp, South Africa. It is one of the most important hominin fossil-bearing sites in the world and finds include the female australopithecine Mrs Ples, discovered in 1947 and recently voted No.95 in a list of 100 Great South Africans. Sterkfontein has yielded stone tools in addition to hominin fossils and it is now part of the Cradle of Humankind, a World Heritage Site named by UNESCO in 1999. Most of the finds have been made in Members 4 and 5 of the cave’s sedimentary sequence, but rather less well known is the large underground chamber known as Milner Hall.

It is from Milner Hall that the discovery is reported of a hominin adult upper right molar (M1) tooth and a proximal phalanx finger bone, probably from a left hand. The chamber has previously yielded only stone tools, and association with these suggests that the fossils are 2.18 million years old.

The tooth is broadly closer to Homo than to Australopithecus or Paranthropus. It most closely resembles the Olduvai OH 6 first molar assigned to Homo habilis and a first molar assigned to the recently-proposed Homo naledi. The shape and size of the tooth’s cusps align it to early Homo.

The finger bone is larger and more robust than that of any hominin so far discovered in South Africa. It resembles the Olduvai Homo habilis fossil OH 7, but is much larger. It is markedly curved, within the range of Australopithecus afarensis and suggesting adaptation for tree-climbing, but it lacks other features associated with arborealism, such as a strongly developed flexor apparatus and a mediolaterally expanded diaphysis; these features are present in A. afarensis, Homo habilis and present-day chimpanzees. The finger bone possesses an enigmatic mixture of primitive, derived and unique characteristics. It is not clear whether or not it belonged to the same individual and its taxonomic affinities are at this stage uncertain.

References:

Stratford, D., Heaton, J., Pickering, T., Caruana, M. & Shadrach, K., First hominin fossils from Milner Hall, Sterkfontein, South Africa. Journal of Human Evolution 91, 167-173 (2016).

 

 

New hominin species reported from Ethiopia

Australopithecus deyiremeda was a contemporary of ‘Lucy’
Hominin remains comprising a complete lower jawbone, a partial lower jawbone and two partial upper jawbones, together with some accompanying teeth have been described as a new species, Australopithecus deyiremeda. The fossils were excavated in 2011 in the Woranso–Mille study area, central Afar, Ethiopia. They were found in deposits dated from 3.3 to 3.5 million years old, making Australopithecus deyiremeda a contemporary of Australopithecus afarensis (the species to which the well-known fossil ‘Lucy’ belongs) and the controversial hominin species Kenyanthropus platyops. The specific name deyiremedameans ‘close relative’ in the local Afar language and follows a now-established tradition of using local languages to name hominin species.
Australopithecus deyiremeda is distinguished from Ardipithecus ramidus by its thicker dental enamel and more robust lower jawbone. It is distinguished from Australopithecus afarensis by a number of features of its lower jawbone, by the positioning of its cheekbones in relation to the upper jawbone, and by its smaller back teeth.
What are the implications of this discovery? For a long time, it was believed that there was just the one hominin species, Australopithecus afarensis, living in the period from four to three million years ago, in East Africa. It was possible to argue that the earlier Australopithecus anamensis (4.2 to 3.9 million years ago) and the later Australopithecus garhi (2.5 million years ago) were simply early and late forms of the same species and that Australopithecus bahrelghazali from Chad (known from a single 3.5-million-year-old specimen) represented a Central African extension of its range. On this view, Australopithecus afarensis was a single, long-lived, geographically widespread species, capable of occupying a wide range of habitats. Not until 2.8 million years ago did other hominin species start to appear: Australopithecus africanus and later Australopithecus sediba in South Africa and the so-called robust australopithecines (Paranthropus) in both South Africa and East Africa.
Even if Kenyanthropus platyops is rejected, this view is no longer tenable. There is now incontrovertible evidence that multiple australopithecine species were living in East Africa during the Middle Pliocene. It is also notable that Australopithecus afarensis has been recorded at Hadar, only 35 km (20 miles) north of Woranso–Mille. Not only did these species overlap in time, they were close in geographical terms, probably occupying differing feeding niches.
Early hominin evolution has been described as more of a tangled bush than a family tree. In addition to Australopithecus afarensis, Australopithecus deyiremeda and possibly Kenyanthropus platyops, it is likely that the Ardipithecusline was still in existence at this time. The Woranso–Mille site has also yielded a 3.4-million-year-old partial hominin foot with an opposable big toe. Though it has not been assigned to a particular species, the toe suggests Ardipithecus or something very similar.
With the LD-50-1 lower jawbone pushing back the origins of Homo to 2.8 million years ago, later australopithecines such as Australopithecus sediba have been bumped from the list of possible human ancestors. However, the Woranso–Mille discovery means that we are no nearer identifying from just which part of the ‘tangled bush’ the first humans emerged.
References:
Haile-Selassie, Y. et al., New species from Ethiopia further expands Middle Pliocene hominin diversity. Nature 521, 483-488 (2015).

Fifty years of Homo habilis

The first human species – or was it?
 
Fifty years ago, the British anthropologist Louis Leakey and two colleagues reported the discovery of a new human species, Homo habilis (‘handy man’), in the journal Nature. Homo habilis lived at least 1.9 million years ago and remains the earliest-known widely-recognised human species to this day. The new species was described from fossils recovered at Olduvai Gorge, Tanzania between 1960 and 1964, but the story of its discovery began more than three decades earlier in 1931, when Leakey first investigated this now world-famous site.

Leakey believed that humans had evolved from African apes, as Darwin had originally suggested. By the early twentieth century however, this view had fallen out of favour and an Asian origin was widely favoured. The earliest-known human species at that time was Homo erectus, which had been discovered in late nineteenth century and was then known only in Asia. Although Neanderthals had been discovered some decades before that, Homo erectus was the first human species to be discovered that lived significantly before Homo sapiens and its brain was only around two-thirds the size of a modern brain.

However, in 1924, Australian anthropologist Raymond Dart had studied an apelike fossil found at a lime quarry at Taung, near Johannesburg, South Africa. He noted that the spinal column entered the skull through the centre rather than the back, suggesting that it was a biped and therefore a very early human – although its brain was no larger than that of a chimpanzee. Dart named it Australopithecus africanus(southern ape from Africa). The discovery switched the focus back to Africa, and in the decades that followed, australopithecines were also found in East and Central Africa. What was missing was a human ancestor intermediate between the australopithecines and Homo erectus.

Leakey became interested in Olduvai Gorge when fossilised human remains were found there, though ironically these later turned out to be a comparatively recent burial. Olduvai Gorge is probably the best-known fossil site in the world, and is now a UNESCO World Heritage site. A steep-sided ravine in Eastern Serengeti, it was formed when a stream carved its way through sedimentary rock, revealing seven main archaeological layers going back two million years. It was originally known as Oldoway Gorge; but it and Olduvai are mispronunciations of the local name Oldupai Gorge, which in turn comes from the Maasai word for the wild sisal plant growing in the gorge.

The 1931 expedition failed to discover any fossils, but a number of stone tools were found. These included a rudimentary stone chopping tool that was made by chipping flakes off a stone cobble to produce a weighty, sharp-edged cutting tool capable of cutting into animal carcasses. The tool is now on display in the British Museum, which at 1.8 million years old is the oldest object in the museum’s collection. Leakey classed the find as Oldowan, for the then still-current name Oldoway Gorge. The tool was found in Bed I, the lowest, earliest archaeological level at the site; more sophisticated stone hand-axes were found in higher, later levels. Leakey believed that the site recorded a sequence leading from the simple chopping tools in the lowest levels to the far more sophisticated tools in the higher Bed IV. The search was now on for the maker of the Oldowan tools, but Leakey’s work was interrupted by the breakup of his marriage and the outbreak of the Second World War.

In 1951, he returned to Olduvai Gorge with his second wife, Mary, and in 1959, after several fruitless seasons, the Leakeys were finally rewarded with the discovery of the fossil skull of a young adult in the same archaeological layer that had yielded the stone cobble tool. It was small-brained and large jawed, with massive chewing teeth. The new species was designated Zinjanthropus boisei; ‘Zinj’ is an ancient Arabic word for the coast of East Africa, and the name also honours expedition sponsor Charles Boise. The skull was given the affectionate nickname of ‘Dear Boy’ by Mary Leakey. Now known as Paranthropus boisei, ‘Dear Boy’ belonged to an offshoot of the australopithecine lineage that is thought to have been an evolutionary dead end. Could this have been the maker of the cobble tools? It seemed doubtful.

The Leakeys were then joined in the field by their son Jonathan, and in November 1960 Jonathan and Mary found a lower jawbone with 13 teeth still in place, together with finger, hand and wrist bones. Over the next three years further fossils were recovered and analysed with the help of primatologist John Napier and anthropologist Phillip Tobias. They came from a species with a larger brain and smaller teeth than ‘Dear Boy’. Louis Leakey believed that this was this was the real toolmaker. The new species was announced in the journal Nature in April 1964 and given a name proposed by Raymond Dart – Homo habilis.

Compared to the australopithecines, the skull of Homo habilis was less massively-built, and the upper and lower jaws were within the size range of both Homo erectus and modern humans. The feet were humanlike, as were the thumb joints – but it was shorter in stature and much smaller-brained than a modern human. Males averaged 5 ft. 1 in and females 4 ft. 1 in; the brain size of around 600 cc was far less than the 1350 cc average for a modern human, or even the 750 cc human minimum proposed by British anthropologist Sir Arthur Keith in the late 1940s. This figure lies midway between the largest gorilla brain and the smallest modern human brain. Homo habilis was nevertheless significantly taller and bigger-brained than the australopithecines. However, the limb proportions were still apelike, with proportionately long arms and short legs, suggesting that Homo habilis retained some apelike tree-climbing abilities.

The Olduvai fossils are 1.8 million years old. Most remains are from East Africa; but the skull STW 53 from Sterkfontein, South Africa, may also be Homo habilis. The oldest tentative fossil evidence for Homo habilis to date is AL 666-1, a 2.33-million-year-old upper jawbone recovered at Hadar, Ethiopia, but the oldest uncontested Homo habilis remains are only 1.9 million years old. The most recent Homo habilis fossil currently known is a 1.44-million-year-old partial upper jawbone from Koobi Fora, Kenya. These dates – if both correct – imply that the species survived for almost a million years. Homo habilis is not known to have left Africa, but it has been suggested that it might have been the ancestor of Homo floresiensis, the so-called ‘hobbit people’ from the Indonesian island of Flores.

The Oldowan stone tool tradition associated with Homo habilis was the most primitive of all stone tool traditions. We now know that such tools were also made by some of the later australopithecines and might have a response to deteriorating climate as the Earth entered the current series of ice ages 2.5 million years ago. It is possible that as the climate deteriorated, preferred food types became unavailable and australopithecines added more meat to their diet. The increased need to butcher carcasses led to the development of stone tools. Early Homo erectus also used Oldowan tools before switching to the more advanced hand-axes seen in the upper levels at Olduvai Gorge. However, many Homo erectus groups, particularly in the Far East, persisted with the Oldowan stone cobble tools.

Plaster casts of the inside of Homo habilis braincases have shown that the sulcal and gyral patterns (ridges and furrows that give the human brain its wrinkled look) were more humanlike than apelike. The frontal and parietal lobes are enlarged, and that the Broca’s Area was expanded in comparison to the same region in australopithecines and modern apes. The frontal lobes, which control higher brain functions including planning and reasoning, are located at the front of the brain. Behind them, on the top and on each side of the brain are the parietal lobes, which carry out a wide range of functions including spatial awareness and the processing of sensory information.

Broca’s Area is named for nineteenth century physician Paul Broca who demonstrated a connection with speech. Damage leads to Broca’s aphasia, where patients are unable to speak in a grammatically correct manner. This suggests some linguistic abilities, though recent research shows that the Broca’s Area is also associated with tool-making. It is possible that its expansion was linked to enhanced tool-making skills as well as or possibly instead of the use of language.

However, the late australopithecines that made stone tools had brains no larger than their forebears, so tool-making alone doesn’t explain why Homo habilis needed a bigger, better brain. Bigger brains might sound like a good idea, but the same could be said of owning a Rolls-Royce. The problem in both cases is that they are expensive to run, and there is a pretty good case for trying to get by without. Brain tissue requires over 22 times as much energy as an equivalent amount of muscle tissue. In a modern human, the brain uses around 16 percent of the body’s energy budget despite making up just 2 percent of the body’s overall mass. While the energy costs of the smaller Homo habilis brain were less than those of a modern human brain, they were still considerable.

A possible answer is the social brain hypothesis, a theory which links the brain size of primates to the size of their social group. The enhanced brainpower is needed to keep track of the complex social relationships that are normal in many primate societies – not just human ones. Larger, more co-operative social groupings in Homo habilis society might have been an evolutionary response to the deteriorating climate and reduced availability of food.

Just where Homo habilisbelongs in the human family tree remains contentious, even half a century after its discovery was announced. Even its membership of the human league is now questioned, with some seeing it as the anthropological equivalent of the now ex-planet Pluto and arguing that it should be reclassified as an australopithecine.

Although most textbooks describe Homo habilis as the ancestor of Homo erectus, the view has been called into question. Recent fossil finds indicate that Homo habilis persisted alongside Homo erectus for hundreds of thousands of year at Koobi Fora, Kenya. This makes it unlikely that the latter evolved from the former, and instead it has been proposed that both shared a common ancestor about two million years ago. If it were to turn out that the disputed AL 666-1 upper jawbone was something other than Homo habilis, then this scenario would become likely as the oldest examples of the two species would then be practically the same age. Another possibility is that the true ancestor of Homo erectus is the recently-discovered australopithecine species Australopithecus sediba. Australopithecus sediba lived in South Africa two million years ago, with limb proportions said to be more humanlike than Homo habilis.

Do the fossils assigned to Homo habilis even represent a single species? The variation in Homo habilis fossils is considerable and it has been suggested that these actually represent two species. Some examples have a broader, flatter face and larger teeth than others, and it is has been proposed that these be assigned to a second species known as Homo rudolfensis. On the other hand, it has been claimed that the degree of variation between skulls assigned to Homo habilis, Homo rudolfensis and Homo erectus is actually no more than that between five early Homo erectus skulls found at Dmanisi, Georgia, and it has accordingly been suggested that all three are actually the same species. The problem with this view is that it does not explain the more apelike limb proportions of Homo habilis.

It is this detail together with the small brain size that has led some to believe that Homo habilisshould be reclassified as an australopithecine. Quite simply, it is too unlike Homo sapiens to be regarded as a human species. However, there is no consensus on the issue. Studies have been conducted to determine whether it can be included in Genus Homo on the basis of anatomical characteristics shared with other members, but these have proved inconclusive.

If Homo habilis individuals could somehow have been aware that they would one day become the subject of such deliberations, it is unlikely that they would have been overly concerned. It should not be forgotten that they might have existed for as long as a million years, which is a testament to their success as a species.

Were multiple early human species living in Georgia, 1.85 million years ago?

New skull with ‘enigmatic’ jawbone and differing tool technologies suggests that two different hominin groups are represented by Dmanisi remains.

The former Soviet republic of Georgia is located at the crossroads of Europe and Asia. Lying on the eastern shores of the Black Sea, it was the destination of Jason and the Argonauts in their quest for the Golden Fleece, but long before this it was a stopping point for the earliest-known hominin migration out of Africa. In 1984, stone tools were discovered at the small medieval town of Dmanisi in the southeast of the country, 93 km (58 miles) southwest of the capital, Tbilisi. Archaeologists broke through the foundations of a medieval building into an ancient river deposit, where simple stone tools resembling those made by the earliest humans were found with the bones of extinct mammals.

During the 1990s, the remains of early humans were recovered, including two partial skulls and a lower jawbone. The fossils were dated by palaeomagnetic, potassium-argon and argon-argon methods, giving an age for the remains of 1.77 million years old (Gabunia, et al., 2000). Subsequent dating of the stone tools indicated that the site was first occupied 1.85 million years ago, and that repeated occupations continued over a period of 80,000 years. There was evidently a long-term human presence in the Caucasus at around or even before the time of the earliest evidence for Homo erectus in Africa (Ferring, et al., 2011).

There have been a number of subsequent discoveries of human remains at the site. These include the skull, lower jawbone and partial skeleton of an adolescent (Vekua, et al., 2002; Lordkipanidze, et al., 2007); the skulls and lower jawbones of two adults (Lordkipanidze, et al., 2006; Lordkipanidze, et al., 2013); and postcranial bones from three other individuals, all adults (Lordkipanidze, et al., 2007). One of the skulls belonged to an elderly male who had lost all but one of his teeth some years prior to his death. He could not have survived unaided and must have been cared for by his companions throughout those last years of his life (Lordkipanidze, et al., 2005; Lordkipanidze, et al., 2006). The other skull, the fifth to be discovered at the site and hence known as Skull 5, is characterised by a large face and thick browridges. Skull 5 is complete and undeformed; it is the only known fully-preserved adult hominin skull from the early Pleistocene (Lordkipanidze, et al., 2013).

From the various remains, body size metrics have been estimated for the Dmanisi hominins. They were 1.45 to 1.66 m (4 ft. 9 in. to 5 ft. 5 in.) tall and weighed 40.0 to 50.0 kg (88 to 110 lb.). The cranial capacities of the five skulls range from 546 to 730 cc, about half that of a modern human. The encephalization quotient (a measure of brain size in relation to body size) lies in the range from 2.4 to 3.13; a figure that is at the lower end of the estimates for African Homo erectus, and is more comparable to that of Homo habilis or Australopithecus (Lordkipanidze, et al., 2007; Lordkipanidze, et al., 2013).

The Dmanisi hominins display a mosaic of primitive and derived (more modern) features. Their limb proportions were similar to those of a modern human. The lower limbs and feet were essentially modern, although the feet turned slightly inwards. On the other hand, the forearm lacked what is known as humeral torsion. In modern humans, the elbow joint is typically rotated relative to the shoulder joint, so that the forearm naturally hangs with the palms facing inwards; but the Dmanisi forearm lacked this rotation, so their palms were oriented more forwards. The inward-turning feet, lack of humeral torsion, small body size and small brain size may be seen as primitive traits, sharing more in common with Homo habilis than with Homo erectus (Lieberman, 2007; Lordkipanidze, et al., 2007).

Initially assigned to African Homo erectus (Vekua, et al., 2002), the Dmanisi hominins were later put forward as a new human species, Homo georgicus (Gabunia, et al., 2002); though this proposal has since been retracted (Lordkipanidze, et al., 2013), and it has been suggested that early African Homo erectus was not only quite widespread, but also unusually variable in both body and brain size, and also less modern than sometimes supposed (Lieberman, 2007).

Two more radical (and diametrically-opposed) possibilities have recently been put forward. The first is that the various species often proposed for early African Homo (Homo habilis, Homo rudolfensis, Homo ergaster and Homo erectus) were all actually variants of the same species, and that early Homo was a single lineage which evolved over time without differentiating into multiple species. This conclusion is based on a claim that shape variation between the five Dmanisi skulls is roughly the same as that seen among the various early Homo skulls from East Africa, even though the former represents a single species and the latter are generally thought to represent several (Lordkipanidze, et al., 2013).

The second proposal (Bermúdez de Castro, et al., 2014) is that Skull 5 represents a different group of early hominins to that of the other Dmanisi remains. The lower jawbone is larger than those of others, and is said to represent a ‘large and somewhat enigmatic individual’. Its shape differs, and the differences cannot be accounted for in terms of body size or sex. It possesses a mosaic of primitive and derived features that are absent from other Dmanisi specimens. Furthermore, patterns of dental wear suggest a higher intake of fibrous and abrasive foods. It has accordingly been suggested that the jawbone is adapted to a different ecological niche to the other Dmanisi hominins, and that it represents a different species.

Although tools document a long-term human presence at Dmanisi, all the actual human remains were found in the same geological layer. This makes the ‘two species’ scenario problematic, as it implies that both species lived at about the same time. However, the stratigraphy of Dmanisi is complex, and it is possible that the fossil remains were re-deposited in the same geological layer after initially occupying sediments of different ages. It has also been claimed that the tools found at Dmanisi are consistent with the existence of two different populations.

More evidence is needed to determine just where the Dmanisi hominins fit into the broader human evolutionary picture, but it is becoming clear that the first hominin dispersal out of Africa was a far more complex process than was at one time supposed.

References:
1. Gabunia, L. et al., Earliest Pleistocene Hominid Cranial Remains from Dmanisi,Republic of Georgia: Taxonomy, Geological Setting, and Age. Science 228, 1019-1025 (2000).

2. Ferring, R. et al., Earliest human occupations at Dmanisi (Georgian Caucasus) dated to 1.85–1.78 Ma. PNAS 108 (26), 10432-10436 (2011).

3. Vekua, A. et al., A New Skull of Early Homo from Dmanisi, Georgia. Science 297, 85-89 (2002).

4. Lordkipanidze, D. et al., Postcranial evidence from early Homo from Dmanisi, Georgia. Nature 449, 305-310 (2007).

5. Lordkipanidze, D. et al., A Fourth Hominin Skull From Dmanisi, Georgia. The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology 288A, 1146–1157 (2006).

6. Lordkipanidze, D. et al., A Complete Skull from Dmanisi, Georgia, and the Evolutionary Biology of Early Homo. Science 342, 326-331 (2013).

7. Lordkipanidze, D. et al., The earliest toothless hominin skull. Nature 434, 717-718 (2005).

8. Lieberman, D., Homing in on early Homo. Nature 449, 291-292 (2007).

9. Gabunia, L., de Lumley, M.-A., Vekua, A., Lordkipanidze, D. & de Lumley, H., Découverte d’un nouvel hominidé à Dmanissi (Transcaucasie, Géorgie). C.R. Palévol. 1, 243–253 (2002).

10. Bermúdez de Castro, J., Martinón-Torres, M., Sier, M. & Martín-Francés, L., On the Variability of the Dmanisi Mandibles. PLoS One 9 (2), e88212 (2014).

Reassessment of 1950s fossil find provides early evidence for hominins in Central Africa

2.0 to 2.6-million-year-old tooth is from australopithecine or early human.

A reassessment of a fossil tooth from an old archaeological collection suggests that early hominins had extended their range to the western branch of Africa’s Great Rift Valley by no later than two million years ago. Since the late 1950s, large numbers of early hominin fossils have been found in the eastern branch of the Great Rift Valley, which is often described as the Cradle of Humanity. However, up until now, none have been found in the western branch.

Ishango 11 is an archaeological site in the Democratic Republic of Congo; it is located alongside the Semliki River, in the western branch of the Great Rift Valley. In the 1950s, the site was excavated by the Belgian geologist Jean de Heinzelin, who recovered numerous fossil human and animal remains, together with stone and bone artefacts. The assemblage dates mainly to the early part of the African Late Stone Age, from 25,000 to 19,000 years ago. It is housed in the Department of Anthropology and Prehistory at the Royal Belgian Institute of Science, Brussels.

However, the finds also included an upper left first molar that did not appear to be from such a recent period. Known as #Ish25, doubts were cast on its affinities to modern humans as long ago as 1958. A recent study has shown that #Ish25 probably originated from an earlier geological layer than the other fossils and artefacts. Animal remains associated with this layer suggest that it dates to between 2.6 and 2.0 million years ago. These dates make #Ish25 the earliest fossil hominin find from the western branch of the Great Rift Valley (though not the earliest from Central Africa, as much earlier hominins are known from Chad).

Various statistical analyses of the shape and size of #Ish25 suggest closer affinities to hominins from the Late Pliocene/Early Pleistocene than those from the Middle Pleistocene to Recent epochs. The exact hominin species to which the tooth belongs cannot be determined with certainty; Australopithecus africanus, Paranthropus robustus and early Homo are all possibilities.

The western Great Rift Valley underwent episodes of climate change 3.0, 2.6 and 1.8 million years ago; these led to the partial replacement of Congo flora and fauna with those typical of the East Africa; the latter are adapted to more open grassland conditions. The #Ish25 findings suggest that these conditions led to a dispersal of hominins into the region from either East Africa or South Africa.

The study also demonstrates how valuable knowledge can often be gained by applying modern techniques to old anthropological collections.

 Reference:

1. Crevecoeur, I. et al., First Early Hominin from Central Africa (Ishango, Democratic Republic of Congo). PLoS One 9 (1), e84652 (2014).