Wednesday, 10 August 2016

Neanderthals lacked specialised cold weather clothing

Study of faunal remains suggest garments with fur trim were made only by modern humans.

Neanderthal use of clothing has long been debated. Even during warm interglacial periods, Neanderthals must have faced a problem with heat-loss in winter. It has been argued that wearing cape-type clothing across the shoulder would not have been sufficient to ward off the cold of even a moderately severe winter or body cooling caused by wind-chill. Clothing and footwear would therefore have had to be sewn together tightly in order to keep out snow and water. (Sørensen, 2009) Despite this, definite evidence for tailored clothing is lacking in Europe prior to the arrival of modern humans, and it has only been found at modern human sites. (Klein, 1999; Hoffecker, 2005)

In an attempt to resolve the issue, a team of researchers led by anthropologist Mark Collard adopted a novel approach. They considered faunal remains found at both Neanderthal and modern human sites and noted species whose skins might have been used to make clothing. They found that although species suitable for making cold-weather garments were found at both Neanderthal and modern human sites, remains of wolves, foxes, rabbits and mink occurred more frequently at modern human sites. These species are used to make garments with fur trim, and it was accordingly argued that Neanderthals did not make such garments and did, after all, rely on cape-type clothing. (Collard, et al., 2016)

References
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Sørensen, B., Energy use by Eem Neanderthals. Journal of Archaeological Science 36 (10), 2201-2005 (2009).
Klein, R., The Human Career, 2nd ed. (University of Chicago Press, Chicago, 1999).
Hoffecker, J., Innovation and Technological Knowledge in the Upper Paleolithic of Northern Eurasia. Evolutionary Anthropology 14, 186-198 (2005).
Collard, M., Tarle, L., Sandgathe, D. & Allan, A., Faunal evidence for a difference in clothing use between Neanderthals and early modern humans in Europe. Journal of Anthropological Archaeology (2016).x


Friday, 29 July 2016

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:
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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


Thursday, 9 June 2016

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
:
x
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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. Nature 441, 624-628 (2006).
Brumm, A. et al., Hominins on Flores, Indonesia, by one million years ago. Nature 464, 748-753 (2010).
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Thursday, 26 May 2016

175,000-year-old underground Neanderthal stone circle

Structure discovered in 1990s is ten times older than Lascaux cave paintings

Bruniquel Cave in southwest France was discovered by members of a local caving club in 1990. The cave’s entrance had been sealed by a landslide during the last Ice Age, but the cavers re-opened a narrow 30m (100 ft.) passage leading into a main gallery of chambers rich in stalagmites and stalactites. Some 336 m (1,000 ft.) from the entrance, they found strange complex of stone circles, constructed from broken stalagmites. Intrigued by the discovery, the cavers brought in archaeologist Francois Rouzaud to investigate.

The complex comprises two circles measuring 6.7 × 4.5 m (22 ft. x 14 ft. 9 in.) and 2.2 × 2.1 m (7 ft. 3 in. x 6 ft. 10 in.) and four smaller stacks of stalagmites, two of which are located inside the larger circle. Around 400 stalagmite fragments were used in the construction, half of which are mid-sections with the tip and base removed. The fragments were standardised in length, leaving no doubt that the structures had been constructed by humans. All six structures show extensive traces of fire, with many of the fragments showing signs of either blackening or reddening.

Rouzaud recovered a burned bone from the largest structure, which was radiocarbon dated and found to be 47,600 years old. This predates the arrival of modern humans in the region, but not sufficiently to rule out the possibility that they were the builders. The only other possibility was Neanderthals – which in the 1990s, was viewed as unlikely. The slow-to-die perception of Neanderthals as dimwits was even more prevalent then. Sadly, before further investigations could be carried, Francois Rouzaud died suddenly, aged just 50. With his death, all work at Bruniquel Cave ceased, and the enigmatic stone circles were forgotten until they came to the attention of geologist Sophie Verheyden.

Verheyden was curious as to why nobody had attempted to date the stalagmites. 47,600 years is close to the useful limit of radiocarbon dating, but uranium series dating can go back much further, and speleothem is very amenable to this method. By applying it to calcite layers that had formed over the stalagmite fragments after the complex was built, it would be fairly straightforward to determine when they had been broken off from the floor of the cave. Verheyden assembled a multi-disciplinary team including archaeologist Jacques Jaubert and geologist Dominique Genty and in 2013, after obtaining permission to study the cave, they resumed the investigation.

The results are reported in the online edition of the journal Nature and they suggest that the Bruniquel Cave stone circles are 176,500 years old – ten times older than the cave paintings of Lascaux. There is not the slightest possibility that they were the work of modern humans, who would not arrive for another 130 millennia. The only hominins living in southwestern France at that time were Neanderthals. The attribution of the Bruniquel constructions to Neanderthals demonstrates that they possessed the sophistication and organisational skills to heat and light a deep underground cavern while they built and used an elaborate structure of a type never before seen elsewhere.

The obvious question now is was the function of these structures, located at such a great distance from the cave entrance? There is no evidence that the cave was used as a living habitat. Had the stone circles dated to the Upper Palaeolithic, nobody would have doubted that the complex was a ritual centre of some kind. It is difficult to avoid the conclusion that it served this function for its Neanderthal builders and as such is further evidence of their capacity for symbolic behaviour.

References:
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1.
Jaubert, J. et al., Early Neanderthal constructions deep in Bruniquel Cave in southwestern France. Nature (Online edition) (2016).
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Wednesday, 27 April 2016

Iron Age origins of European Alpine dairy farming

Chemical analysis of organic residues from pottery reveals lipids

Dairy produce from the high Alps is today of enormous economic and cultural importance to the region. The recent history of dairy farming is well-documented, but there is very little in the way of archaeological evidence to attest to its origins. Transhumance (seasonal migration of livestock between pastures) leaves few traces, and the problem is compounded by acidic soils that lead to the deterioration of faunal remains.  

Milk production in lowland settings in Europe is documented from the Early Neolithic, and ceramic sieves for separating curds and whey are evidence for the production of cheese and fermented milk products by populations that were still predominantly lactose intolerant. In the Alpine lowlands, there is evidence for dairy farming in the form of lipid residues on pottery vessels from around 6,000 BC. However, it was at this stage part of a generalised mixed farming economy that also included meat production.  

From around 3000 BC, it has been speculated that dairy farming intensified as there was a greater reliance on ‘secondary’ animal products such as wool and milk, and greater utilisation of poorer and less accessible land. As noted above, the limited supporting archaeological evidence is not unexpected. Seasonal occupation of high-altitudes intensified from around 2500 BC to 1000 BC and large dry stone enclosures were constructed during this period. They are thought to be livestock pens, but the scarcity of artefacts or faunal remains means that there is no definite clues as to their function. The only ceramics to have been recovered from these sites are small, highly fragmented potsherds.

To investigate further, researchers obtained 30 securely-dated potsherds from six highland archaeological sites of the Engadin region of southern Switzerland. The sites dated from 5000 to 1000 BC. The region is typical of the alpine environment, with valley bottoms above 1,000 m above sea level and high seasonal pastures ranging from around 2,000 m to 2,800 m above sea level. Five of the sites were more than 2,000 m above sea level. They include early Neolithic and Bronze Age rock-shelters and a later Iron Age stone enclosure and hut.

Lipids were successfully extracted in varying amounts from the potsherds, with all the Iron Age pots yielding much higher quantities. Analysis of the lipids using gas chromatography mass spectrometry revealed profiles typical of degraded animal fats. Several Bronze Age and Iron Age potsherds contained ketones with chain lengths consistent with heating of saturated fatty acids, suggesting that the pots were used for heating animal products.

Carbon stable isotope analysis was then applied to fatty acids obtained from 28 of the potsherds. The milk of ruminants and to a lesser extent carcass fat of ruminants, is depleted in 13C relative to other fatty acids. Values obtained were then compared with those obtained from dairy, ruminant and non-ruminant sources. It was found that values for lipids obtained from the Iron Age potsherds were consistent with dairy products. By contrast, the earlier Neolithic and Bronze Age potsherds yielded values consistent with ruminant and non-ruminant animal fats. Dairy farming was identified at all of the Iron Age sites included in the study.

Thus it appears that while low-altitude dairy farming was present from the Neolithic onwards, specialist Alpine dairy farming was a later development. Iron Age alpine pastoralists would have had to face adverse and unpredictable weather, and a significant reduction in the yield and quality of milk. It is likely that pressure on lowland pastures and an increased demand for alpine cheese were motivating factors. This in turn was probably triggered by social and economic changes, deterioration of the climate, and demographic growth during the Late Bronze Age and the Early Iron Age.

Reference:x
Carrer, F. et al., Chemical Analysis of Pottery Demonstrates Prehistoric Origin for High-Altitude Alpine Dairying. PLoS One 11 (4), DOI:10.1371/journal.pone.0151442 (2016).
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Thursday, 7 April 2016

No Neanderthal-derived Y-chromosomes in modern population

Evidence found of genetic incompatibility

An open access study published in The American Journal of Human Genetics has found no evidence of Neanderthal introgression into modern male Y-chromosome despite it being elsewhere in the modern genome. The study is the first in which a Neanderthal Y-chromosome has been sequenced as all the Neanderthal individuals previously sequenced to 0.1x coverage were women. Women do not have a Y-chromosome, so men inherit their Y-chromosomal DNA exclusively from their fathers. The researchers sequenced the Y-chromosome from a male Neanderthal from the El Sidrón cave site in northern Spain, dating to 49,000 years ago.

The researchers found that the Neanderthal and modern human Y-chromosomes diverged from one another around 588,000 years ago, which is consistent with estimates for when the ancestors of Neanderthals and modern humans diverged from one another. This was not unexpected: the surprise was that no Neanderthal-derived Y-chromosome has ever been observed in a modern male. While this could simply be the result of genetic drift, the researchers found evidence of genetic incompatibility between the Y-chromosomal genes of Neanderthals and modern humans.

They identified protein-coding differences between Neanderthal and modern human Y-chromosomes, including potentially deleterious coding differences in the genes PCDH11Y, TMSB4Y, USP9Y and KDM5D. PCDH11Y and its X-chromosomal counterpart PCDH11X might play a role in brain lateralisation and language development; TMSB4Y might influence sperm production; USP9Y might reduce cell proliferation in malignant tumours; and KDM5D might play a role in suppressing the invasiveness of certain cancers.

Three of these changes are missense mutations, i.e. they alter the amino acid sequence of proteins, which in turn have a biological impact. All three are in genes that produce male-specific minor histocompatibility (H-Y) antigens. Such antigens can trigger an immune response during pregnancy, leading to a miscarriage. These antigens are similar to human leucocyte antigens (HLA) that form part of the body’s immune system, but because the genes are on the Y-chromosome they are specific to men. If only girls were carried to full term, that could explain the absence of any Neanderthal contribution to the present-day Y-chromosome.

Reference:
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Mendez, F., Poznik, D., Castellano, S. & Bustamante, C., The Divergence of Neandertal and Modern Human Y Chromosomes. The American Journal of Human Genetics 98, 728-734 (2016).x

Thursday, 31 March 2016

Flores ‘hobbits’ died out much earlier than originally thought

Homo floresiensis extinct by 50,000 years ago

A new study published in Nature has suggested that Homo floresiensis became extinct much earlier than originally reported. The type specimen LB 1, recovered from Late Pleistocene sediments at Liang Bua, Flores in 2004 was claimed to be 18,000 years old, with other remains and associated stone tools dating from 74,000 to 95,000 years old. The dates were inferred from radiocarbon, thermoluminescence, uranium series and electron spin resonance dates on associated sedimentary material. No direct dates were obtained from the remains themselves for fear of damaging them. However, some authorities were dubious that the ‘hobbits’ could have survived for so long after modern humans reached Southeast Asia.

It has now been discovered that the hominin remains and artefacts were found in a stratigraphic sequence of older sediment forming a pedestal, which have been truncated by one or more phases of erosion and subsequently covered by later sediment. This was not recognised during the original excavations, hence making the accuracy of the inferred dates suspect.

The new dates have been obtained by dating the main stratigraphic units within the pedestal; and this time direct dating was also applied to the skeletal remains of Homo floresiensis. Radiocarbon, thermoluminescence, and uranium series methods were used. The revised dates suggest that the skeletal remains range from 60,000 to 100,000 years old and the associated stone tools range from 50,000 to 190,000 years old.

Parts of Southeast Asia may have been inhabited by Denisovans during this period, and modern humans reached Australia by 50,000 years ago. Whether either came into contact with Homo floresiensis or were connected to its demise is at this stage still unknown.

Reference:
Sutikna, T.
et al., Revised stratigraphy and chronology for Homo floresiensis at Liang Bua in Indonesia. Nature, doi:10.1038/nature17179 (2016).


Sunday, 20 March 2016

Melanesian genomes reveal episodes of interbreeding with Neanderthals and Denisovans

Study demonstrates multiple encounters with archaic humans

In a new attempt to obtain genetic information about Neanderthals and Denisovans, researchers have analysed the genomes of 1,523 genetically-diverse individuals, including 35 Melanesians. Results were compared with known Neanderthal and Denisovan sequences. 1340 Mb of the Neanderthal genome and 304 Mb of the Denisovan genome were obtained.

The Melanesians show between 1.9 and 3.4 percent of Denisovan ancestry. They have an average 104 Mb of archaic sequences: 48.9 Mb of Neanderthal, 42.9 Mb of Denisovan, and 12.2 Mb of ambiguous sequence that could be either. By contrast, only 0.026 Mb (in Esan) to 0.5 Mb (in Luhya) of archaic sequences per individual were found in Africans. An average 65.0 Mb of archaic sequences were found in East Asians; 55.2 Mb in South Asians; and 51.2 Mb in Europeans. Most of these archaic sequences were Neanderthal in origin, although a small fraction (less than 1 percent) in East Asians and South Asians are predicted to be Denisovan. There was evidence for an additional pulse of Neanderthal admixture in Europeans, East Asians, and South Asians compared to Melanesians. The data suggests that there were at least three separate episodes of interbreeding between Neanderthals and modern humans, and one of modern humans interbreeding with Denisovans.

The study also found a statistically-significant overlap between regions depleted of Neanderthal and regions depleted of Denisovan genetic sequences, suggesting that archaic sequences in these regions were deleterious and were purged by the effects of purifying selection. Regions depleted of archaic lineages are contain large numbers of genes associated with specific regions of the brain, particularly in the developing cortex and adult striatum. A large region depleted of archaic sequences spans 11 Mb on chromosome 7 and contains the FOXP2 gene associated with speech and language, as well as genes associated with autism.

It is likely that further studies will reveal an increasingly complex picture of how modern humans have interbred with archaic humans throughout Eurasia. The depletion of archaic sequences from brain-related sequences of the genome might hint at cognitive differences between modern and archaic humans; or these regions might simply be more prone to adverse effects of horizontal gene transfer.

Reference:
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Vernot, B. et al., Excavating Neandertal and Denisovan DNA from the genomes of Melanesian individuals (10.1126/science.aad9416) (2016).x


Friday, 18 March 2016

The mammoth diet of Neanderthals

Stable isotope evidence from three Belgian sites

Attempts to gain insight into Neanderthal diet have been many and various over the years. Methods have included consideration of dental microwear, tooth calculus, lithic use-wear and residues, and stable carbon and nitrogen isotope data. These studies have shown that the Neanderthal diet included the consumption of large herbivores, but the extent to which smaller mammals, birds, riverine and seafood was eaten remains uncertain.

To address these issues, researchers conducted carbon and nitrogen stable isotope analyses of collagen extracted from Neanderthal remains from the Belgian sites of Goyet and Spy. Results were compared with those from extensive faunal remains from Goyet, Spy and a third Belgian site, Scladina. These included mammoth, rhino, horse, reindeer, hyena, wolf, cave bear and cave lions. The proportion of the isotopes carbon-13 and nitrogen-15 reflect an animal’s place in the food chain: the highest levels are found in carnivores.

The results show that Neanderthal isotope levels and hence diet differed from that of any carnivore, indicating that they occupied a distinct ecological niche. The overall data suggested that while predators typically preferred smaller animals such as reindeer and horse, the Neanderthal focus was on large herbivores. Mammoth was the most important source of meat, accounting for around 30 to 40 percent of the Neanderthal diet. Reindeer and rhino accounted for lesser proportions, and plant food for about 20 percent.

Reference:
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Wißing, C. et al., Isotopic evidence for dietary ecology of late Neandertals in North-Western Europe. Quaternary International, http://dx.doi.org/10.1016/j.quaint.2015.09.091 (2015).x


Thursday, 17 March 2016

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:
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Meyer, M. et al., Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins. Nature (Published online) (2016).
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Thursday, 10 March 2016

Meat-eating and food processing were major drivers of human evolution

Study shows how dietary changes and stone tools enabled reductions in size of teeth, jaws and gut

In comparison to earlier hominins, Homo erectus was bigger both in stature and brain size. As such, its energy requirements would have increased – but paradoxically the teeth and chewing muscles were smaller, maximum bite forces weaker and the gut size was reduced. It has long been assumed that this was made possible by increased meat consumption, slicing and pounding food with stone tools, and by cooking. However, the latter was uncommon until around 500,000 years ago. By these means, it is believed that Homo erectus and later humans reduced the both amount of chewing required for their food and workload of the gut in digesting it.

In a newly-published study, Zink and Lieberman report on a series of experiments intended to test these hypotheses. They measured chewing performance in adult human subjects fed size-standardized portions of meat and underground storage organs (roots, tubers, etc.) which are thought to have formed a major component of hominin diet. Goat meat, yams, carrots and beets were chosen for the test; goat is tougher than beef and therefore more similar to the wild game eaten by early hominins. The food was either unprocessed, processed by simple mechanical methods available in Lower Palaeolithic times (slicing and pounding), or roasted (the simplest form of cooking).

They found that the subjects were unable to chew the raw meat effectively, but slicing it resulted in substantial reductions in both the amount of chewing and bite forces required, and in smaller and more digestible meat particles were swallowed. Roasted meat required a greater chewing effort, but even smaller meat particles resulted. However, even unprocessed meat required considerably less masticatory effort than the raw USOs.

Although the advent cooking brought considerable benefits in terms of hygiene and increased energy yields, Zink and Lieberman believe that the reductions in dental size and jaw musculature observed in Homo erectus would have been made possible by the combined effects of eating more meat and mechanically processing both it and USOs. By eating a diet of one-third meat and two-thirds USOs, and slicing the meat and pounding the USOs with stone tools prior to eating, early humans would have reduced chewing by 17 percent and enabled a 26 percent reduction in bite forces.

Although it is possible that food processing and meat eating favoured evolutionary selection for smaller teeth and jaws, Zink and Lieberman believe that it is more likely that these relaxed the selective pressures maintaining robust masticatory anatomy, thus enabling selection to decrease facial and dental size for other functions such as speech production, locomotion, thermoregulation, and possibly even changes in the size and shape of the brain, so leading eventually to the modern condition of Homo. Regardless of what evolutionary factors favoured these changes, they would not have been possible without increased meat eating combined with food processing technology.

Reference:
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Zink, K. & Lieberman, D., Impact of meat and Lower Palaeolithic food processing techniques on chewing in humans. Nature (Published online) (2016).

Tuesday, 1 March 2016

Did Neanderthals use manganese dioxide to start fires?

Mineral might have been sought for its combustion enhancing properties rather than as black pigment

Manganese dioxide minerals have been found at a number of Neanderthals sites in Europe, including Pech-de-l’Azé I in the Dordogne region of southern France. The site is around 50,000 years old, predating the arrival of modern humans in Europe. Over the last sixty years, the site has yielded several hundred small ‘blocs’ of black mineral, thought to  be manganese dioxide, and totaling 750 gm in weight. The majority have been ground to obtain powder.

The long-standing view is that powdered manganese dioxide was used as a black pigment, but this view is challenged in a newly-published study. Although manganese dioxide minerals are reasonably abundant, it would have been far easier for Neanderthals to use charcoal and soot from their campfires as black pigment. Also, the evidence from other sites suggests that Neanderthals favoured manganese dioxide over other locally-available manganese minerals, even though the latter would yield equally-satisfactory black pigment. This led the researchers to consider uses for which only manganese dioxide would suffice.

Manganese dioxide is not combustible, but it is a powerful oxidising agent and thus aids the combustion of other materials. The researchers found that when industrial powdered manganese dioxide was mixed with wood turnings, the latter ignited at a temperature of 250 degrees Celsius, over a hundred degrees below the normal ignition temperature. Furthermore, the rate of charcoal combustion was substantially increased. As little as six percent by weight of manganese dioxide was required. The same results were obtained with powder obtained from the Pech-de-l’Azé I blocs.

Based on these experiments, the researchers concluded the Neanderthals’ chief use for manganese dioxide was for starting fires rather than pigment. With archaeological evidence for fireplaces and the production of manganese dioxide to powder, they suggest that the Neanderthals at Pech-de-l’Azé I were able to produce fire as required rather than having to make opportunistic use of lightning strikes and forest fires.

Reference:
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Heyes, P. et al., Selection and Use of Manganese Dioxide by Neanderthals. Scientific Reports 6 (22159 ), doi:10.1038/srep22159 (2016).


Thursday, 18 February 2016

Modern humans interbred with Neanderthals 100,000 years ago

Ancient DNA from Altai Neanderthal female is first evidence of modern human contribution to Neanderthal genome

Ever since the first draft of the Neanderthal genome was published in 2010, it has been known that Neanderthals interbred with modern humans and it is now believed that around twenty percent of their genome survives in the present-day population. Subsequent work revealed the existence of a new human species in the Russian Altai, the Denisovans, and that parts of their genome also survive in the present-day population. It has also been established that the Altai Denisovans also interbred with Neanderthals in the region and with another as yet unidentified archaic species (probably Homo erectus). What has hitherto been absent up is evidence of gene flow from early modern humans into archaic genomes.

To address this issue, researchers investigated the previously-sequenced genome of a Neanderthal woman who lived in the Altai region 50,000 years ago. They found evidence of gene flow from modern humans into the ancestors of the Altai Neanderthal. The source was unclear, but was thought to be a modern population that either split from the ancestors of all present-day Africans, or was one of the early modern African lineages. It was estimated that the implied interbreeding occurred at least 100,000 years ago – well before the previously-reported gene flow from Neanderthals into modern humans outside Africa 47,000 to 65,000 years ago. However, they did not find evidence for similar gene flow from modern humans into either Denisovans or European Neanderthals.

The traditional view that modern humans did not leave Africa and the Levantine/Arabian region until around 60,000 years ago has been refuted by the discovery of teeth lying within the modern range at Fuyan Cave, China, dating to around 100,000 years ago. If modern humans were in China then it is entirely possible that they were also in the Altai at that time. Other possibilities are the Arabian Peninsula, where there is archaeological (though no fossil) evidence for a modern human presence as long ago as 127,000 years ago and Neanderthals were likely to also have been present; and the Levant where there is fossil evidence for both Neanderthals (Tabun) and modern humans (Skhul and Qafzeh) 120,000 to 110,000 years ago.

Reference:
Kuhlwilm, M. et al., Ancient gene flow from early modern humans into Eastern Neanderthals. Nature, doi:10.1038/nature16544 (2015).
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Tuesday, 16 February 2016

Flores ‘hobbits’ arose from an archaic human species

Study confirms that Flores hominins are not Homo sapiens  

Since their headline-making discovery in 2003, the diminutive hominins from the Indonesian island of Flores have been generally accepted to be a distinctive human species, Homo floresiensis. Popularly referred to as ‘hobbits’, they are widely believed that they owe their small size to a phenomenon known as ‘insular dwarfism’. In the absence of dangerous predators and in a habitat where food is scarce, it was suggested that they ‘downsized’ from their ancestral condition as evolution favoured smaller, less ‘gas-guzzling’ individuals. The ancestral species is often claimed to be Homo erectus, but claims have also been made for more primitive hominins such as Homo habilis or even Australopithecus.

Not everybody accepted that Homo floresiensis was a new human species and among the sceptics was the late Teuku Jacob, an Indonesian anthropologist who claimed that the ‘hobbits’ were modern humans affected by a developmental disorder known as microcephaly. Some years after Jacob’s death, his former colleagues revived the theory, this time claiming that Homo floresiensis were modern humans suffering from Down syndrome.

A newly-published study describes the investigation of the cranial bones of the partial female skeleton LB 1 (popularly and perhaps inevitably known as ‘Flo’). A series of high-resolution scans were taken using an X-ray CT scanner. Comparative scans were also taken of microcephalic specimens used in earlier studies of LB 1. The scans were used to study the bone thickness distribution of the cranial vault and internal bone composition and structure. Cranial vault thickness (CVT) can be diagnostic of a hominin species attribution, and it was found to be thick for LB 1 in absolute terms and even more so in relative terms when the small cranial size is taken into account. By contrast, microcephalic skulls of modern humans are thinner than those of humans unaffected by the condition. It was found that Flo had suffered from a condition known as bilateral hyperostosis frontalis interna, and bore the healed scar of a head injury, but there was nothing to indicate that she had suffered from any developmental disorders of the type suggested by Jacob or his former colleagues.

The researchers showed that LB 1 displays characteristics related to the distribution of bone thickness and arrangements of cranial structures that are primitive traits for hominins, differing from the derived condition of modern humans. This was not seen with the microcephalic skulls.

The study thus rules out the possibility that LB 1 can be assigned to Homo sapiens, but leaves the issue of its true affinities unresolved.

Reference:
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Balzeau, A. & Charlier, P., What do cranial bones of LB1 tell us about Homo floresiensis? Journal of Human Evolution 93, 12-24 (2016).
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Friday, 12 February 2016

Adverse effects of interbreeding with Neanderthals

Not all ‘imported’ genes were beneficial

Interbreeding with Neanderthals and Denisovans is believed to have introduced many beneficial genes into the modern genome, helping the immune systems of early modern humans to fight pathogens to which they had not previously been exposed. Other ‘imported’ genes include those involved with the production of keratin, a protein that is used in skin, hair and nails, and in East Asian populations, many genes involved with protection from the sun’s UV rays are of Neanderthal origin. It is likely that the transfer of these genes helped early modern humans to adapt to conditions away from their African homeland.

However, a newly-published study suggests that interbreeding with Neanderthals also had a down side. Researchers analysed the electronic health records (EHR) of 28,000 individuals of European origin and integrated the data with high resolution maps of Neanderthal haplotypes across individual modern human genomes. They carried out a large-scale assessment of the functional effects of DNA inherited from Neanderthals on health-related traits in these individuals. Particular use was made of genotype and phenotype data from the Electronic Medical Records and Genomics Network, which is a consortium that links EHR systems combined with patient genetic data from nine sites across the USA.

Genes of Neanderthal origin were found to be associated with smoking addiction, increased risk of depression, incontinence, bladder pain, urinary tract disorders, protein calorie malnutrition, and actinic keratosis (precancerous skin lesions resulting from exposure to the sun). One gene variant was associated with blood coagulation, increasing the risk of strokes. These results follow on from earlier work which implicated increased risk of Crohn’s disease and type 2 diabetes with Neanderthal genes.

Many of these genes would have been advantageous to Neanderthals: for example, the benefits of enhanced blood coagulation would have greatly outweighed the risk of strokes when injuries leading to significant loss of blood were a part of daily life and few people lived past forty. In other cases, genes were probably once advantageous but adverse effects were triggered by the changes in diet following the coming of agriculture in Neolithic times.
Depression can be triggered by disturbed circadian rhythms. It is possible that Neanderthal brain chemistry and skin responses to sunlight were both linked to the lighting conditions and lifestyles of an era when artificial light consisted of torches and camp fires. In which case, the genes might only have become maladaptive with the advent of widespread artificial lighting.
The methodology used by the researchers is likely to provide further insight into the genetic impact of these ancient encounters between Neanderthals and modern humans.

References:
Simonti, C. et al., The phenotypic legacy of admixture between modern humans and Neandertals. Science 351 (6274), 737-741 (2016).
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Thursday, 11 February 2016

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:
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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).x


Friday, 29 January 2016

Study refutes claim for early cat domestication in China

Quanhucun ‘cats’ were a different feline species

Genetic studies suggest that the domestic cat (Felis silvestris catus) is descended from the Near Eastern Wildcat (Felis silvestris lybica), a subspecies of the widely-distributed Old World Wildcat. The latter has been associated with humans since the early Neolithic, initially as a commensal that preyed on rodents and other pests in early faming settlements. A cat burial from Cyprus, dating to 7350 BC, shows that cats were valued by humans by this time, but domestication was a much later development. The Cypriot cat was large even for a wildcat and well above the size range for a domestic cat.

In 2014, archaeologists claimed to have found evidence for cat domestication in China from around 3500 BC. The Neolithic site of Quanhucun in Shaanxi Province is associated with millet farmers, who had evidently employed cats to tackle the constant threat of rats and mice to their grain. Stable isotope analysis indicates that the many rats and mice whose remains were found fed on the millet, but in turn they were preyed upon by the cats. The cats were within the modern size range, suggesting that they were domesticated although China lies well beyond the geographical range of the Near Eastern Wildcat. The discovery opened up the possibility that domesticated cats had made their way eastwards from Southwest Asia, or that the Quanhucun cats were domesticated locally from an East Asian subspecies of the Old World Wildcat.

It now turns out that neither was the case. An assessment of the remains by another group of researchers has found that the Quanhucun cats were not domesticated Near Eastern Wildcats but leopard cats (Prionailurus bengalensis), a small wildcat native to the region. The Quanhucun cats seem to have been a domestication of a completely different species of wildcat, but it was evidently not successful in the long term. Domesticated Near Eastern Wildcats reached China around 500 BC, and it is from these that all present-day Chinese cats are descended.

References:
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1.  Vigne, J. et al., Earliest “Domestic” Cats in China Identified as Leopard Cat (Prionailurus bengalensis). PLoS One 11 (1) (2016).
2.  Hu, Y. et al., Earliest evidence for commensal processes of cat domestication. PNAS 111 (1), 116-120 (2014).x

Friday, 22 January 2016

Death at Lake Turkana

Evidence of inter-group violence between East African hunter-gatherers 10,000 years ago

Inter-group violence has long played a part in human affairs, but just how long is unclear. Over the last thirty years, evidence has accumulated that massacres were a frequent occurrence in Neolithic Europe. Mass graves have been found at a number of sites associated with the Linearbandkeramik (LBK) culture dating to around 5,000 BC. In all cases, the victims appeared to have been attacked and killed with weapons associated with farming groups suggesting internecine conflict between LBK groups rather than attacks by local hunter-gatherers.

Evidence has now emerged of much earlier inter-group violence involving hunter-gatherers at Nataruk, west of Lake Turkana, Kenya. At the time in question, the lake extended around 30 km (18 miles) beyond its present limits and Nataruk would have been located near its western margins.

In 2012, the remains of at least 27 individuals were discovered, partly or completely exposed upon the surface of a gravel bar ridge. Most were found fully exposed and fragmented, surviving in varying states of preservation and erosion; 12 individuals were partly preserved articulated in situ. Among these, no burial pit was identified, and no preferred orientation or position of head, face, or body was noted. The total number of individuals at the site is unknown, as only those partly exposed were excavated. The remains included 21 adults (8 men, 8 women, the others of unknown sex) and 6 children. One of the women was in the third trimester of pregnancy.

Excavations also revealed stone tools similar to other Later Stone Age assemblages in the area; and fragments of bone harpoons typical of Early Holocene hunter-fishers of Lake Turkana. The skeletal remains lacked collagen so radiocarbon dates were obtained from associated sediments and shells, and an optically stimulated luminescent date was obtained from lake sediments. Based on these, it was estimated that the Nataruk human remains dated to between 9,500 and 10,500 years ago; consistent with dates obtained for shells, harpoons, and charcoal from sites in the immediate vicinity, and corresponding to a period of early Holocene high water levels in Lake Turkana.

10 of the 12 skeletons found in situ show evidence of major trauma that would have proved fatal in the immediate-to-short term, including five or possibly six cases of head and/or neck probably caused by arrows; five cases of head injury inflicted by a blunt instrument; two cases of knee fracture; two cases of multiple fractures to the right hand; and once case of fractured ribs. Only two of these skeletons show no obvious injury. Four of the skeletons, including both that lacked injuries may have been bound hand and possibly foot at time of death. Three artefacts were found within or embedded in two of the bodies: an obsidian bladelet embedded in a male skull; and a chert lunate and obsidian trapeze, found inside the pelvic and thoracic cavities of a male skeleton. Both the injuries and the embedded projectile points are considered to be diagnostic of inter-group conflict, although there was no evidence of scalping or other trophy-taking, which often observed in prehistoric warfare.

West Turkana at this time supported a substantial hunter-gatherer population. The Nataruk massacre might have resulted from a raid for territory, women, children and stored food. The pursuit of these resources would in later agricultural times make violent attacks upon settlements and the need to defend against these an ever present fact of life. Alternatively, it might have been a simple antagonistic response as two groups came into contact.
I
n either case, the deaths at Nataruk are a depressing testimony to the antiquity of inter-group violence and warfare.

References:
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Lahr, M. et al., Inter-group violence among early Holocene hunter-gatherers of West Turkana.; Kenya. Nature 529, 394-398 (2016).
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Friday, 15 January 2016

Humans were in the Arctic 45,000 years ago

Evidence for a human presence inside the Arctic Circle 15,000 years earlier than previously believed

In 2012, archaeologists recovered the remains of a woolly mammoth from frozen sediment on a coastal bluff on the eastern shore of Yenisei Bay, 1.8 km (1.1 miles) north of the Sopochnaya Karga weather station, at 71°54′19.2″N 82°4′23.5″E. The mammoth had clearly been killed by humans, and radiocarbon dating has established that the remains are 45,000 years old.
Previously, the earliest evidence for a human presence inside the Arctic Circle is the Yana Rhinoceros Horn site on the Lower Yana River at 71°N. Artefacts recovered at this site include spear shafts made from rhinoceros and mammoth horn, and a variety of stone tools. The site dates to around 30,000 years ago.

However, the Sopochnaya Karga evidence suggests that humans had mastered the challenging conditions of the Arctic well before this date. Damage and injuries to the mammoth’s ribs, shoulder blades, tusks and lower jawbone were consistent with it having been attacked and killed with thrusting spears and light projectile weapons, and subsequently butchered.

The hunters are assumed to be modern humans, though in the absence of fossil evidence this cannot be confirmed. There is fossil and ancient DNA evidence confirming that modern humans were at Ust’-Ishim in western Siberia 45,000 years ago, but this site lies well to the south at 57°N.

Reference:
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Pitulko, V. et al., Early human presence in the Arctic: Evidence from 45,000-year-old mammoth remains. Science 351 (6270), 260-263 (2016).x


Friday, 8 January 2016

‘Iceman’ stomach bug points to more complex picture of early European settlement

Researchers obtain genome of Helicobacter pylori from 5,000-year-old stomach contents

The stomach bacterium Helicobacter pylori is found in roughly half of the world’s present-day population, although it causes symptoms in only around 10 to 15 percent of cases. The bacterium’s association with humans is very ancient, possibly originating in East Africa 58,000 years ago. Since then, various strains have emerged as humans dispersed around the world. Thus differing strains reflect differing geographical origins and are informative about past human migrations.

The European strain hpEurope is believed to have resulted from hybridization between two ancestral strains known as AE1 and AE2. It is thought that AE1 emerged in Central Asia and later evolved into the present-day strain hpAsia2. AE2 is thought to have arisen in Northeast Africa. The two strains have been thought to have hybridized in Southwest Asia 50,000 years ago, with the recombined strain arriving in Europe when populations expanded after the Last Glacial Maximum.

To test this model, researchers obtained a genome of the bacterium from the stomach contents of ‘Ötzi’, the frozen 5,000 year old corpse that was found in 1991 in the Ötztal Alps on the border between Austria and Italy. Despite the age of Ötzi’s remains, it was thought that any H. pylori present would be similar to the present-day hpEurope strain.

Instead, it turned out that Ötzi was carrying a strain that most closely resembled hpAsia2, which is rare in modern Europeans. This suggests that the hybridisation with the African H. pylori strain actually occurred more recently than 5,000 years ago, in turn implying that there was a Chalcolithic migration from Africa. The study presents interesting evidence that the history of human settlement of Europe during this period is more complex than previously believed.

Reference
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Maixner, F., Krause-Kyora, B., Turaev, D., Herbig, A. & Hoopmann, M., The 5300-year-old Helicobacter pylori genome of the Iceman. Science 351 (6269), 162-165 (2016).
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Friday, 18 December 2015

Did Chinese Homo erectus survive into the Late Pleistocene?

14,000-year-old hominin thigh bone has archaic affinities.

In 2012, human remains differing from the modern condition were reported from two sites 300 km (185 miles) apart in southwest China: Longlin Cave in Guangxi Province, and Maludong (‘Red Deer Cave’) in Yunnan Province. The Longlin remains have been radiocarbon dated to 11,500 years old, and those from Maludong to 14,000 years old. The Longlin remains included a partial skull, a temporal bone fragment probably belonging to the skull, a partial lower jawbone and some fragmentary postcranial bones. The cheek bones of the skull are broad and flared sideways; the browridges conspicuous; the chin less prominent than in Homo sapiens; and the remains are very robust. The Maludong remains include a skullcap, two partial jawbones and a partial thighbone.

Popularly reported as the Red Deer Cave people, the hominins were at first thought to represent a single population, but newly-published work suggests that the Longlin skull has affinities to early modern humans. The bony labyrinth (the bony outer wall of the inner ear) of the temporal bone fragment is modern in appearance and it is possible that the skull’s unusual shape might be the result of interbreeding between archaic and modern humans. It has been suggested that Longlin was located in a ‘hybrid zone’ – a border between relict archaic and modern populations. Similar hybrid zones occur with some non-human primate populations.

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The Maludong thighbone is now claimed to show affinities to archaic humans, in particular those from the Early Pleistocene. There is a scarcity of later archaic human remains in East Asia, and the authors of the new report are reluctant to assign the thighbone to a particular archaic human species. However, the likeliest possibility is that the thighbone represents a late survival of Homo erectus in China. Regardless of species, the implications of these new findings is that isolated populations of archaic humans were still in existence in China as late as 11,500 years ago and that some of these populations were interbreeding with modern humans.

References:

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1.  Curnoe, D. et al., Human Remains from the Pleistocene-Holocene Transition of Southwest China Suggest a Complex Evolutionary History for East Asians. PLoS One 7 (3) (2012).
2.  Curnoe, D., Ji, X., Taçon, P. & Yaozheng, G., Possible Signatures of Hominin Hybridization from the Early Holocene of Southwest China. Scientific Reports 5, 12408 (2015).
3.  Curnoe, D. et al., A Hominin Femur with Archaic Affinities from the Late Pleistocene of Southwest China. PLoS One (2015).
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Thursday, 19 November 2015

New dates for Monte Verde pushes back arrival of first humans in South America

Chilean site was first occupied at least 18,500 years ago

Monte Verde in southern Chile is a peat bog in the terraces of Chinchihuapi Creek in the Maullín river basin, midway between the Pacific coast and the Andean mountains. There is well-preserved evidence of human occupation including wooden tent remains, foundations and floors of huts, hearths, wooden lances, mortars, and large numbers of stone tools. The site was apparently occupied all year round. A wide range of coastal and mountain habitats were exploited including marshes, wetlands, forests, estuaries, and rocky and sandy shorelines.

Evidence of habitation was not thought to pre-date the 14,600 year horizon identified at the site MV-II, although there was evidence of an earlier cultural horizon (MV-I). The MV-II dates in themselves made Monte Verde attractive to opponents of the long-running ‘Clovis First’ orthodoxy, which holds that the culture originally identified at Clovis, New Mexico represents the earliest human settlement of the New World. The Clovis culture is noted for its distinctive leaf-shaped spear points, which were first found in the 1930s. Clovis sites dating from 13,250 years ago are widespread across the United States and Central America to as far south as Panama. Assuming that the first Americans reached the New World via the Beringia land bridge that linked Alaska with Siberia during the last Ice Age, a human presence in South America 14,600 years ago is problematic to Clovis First.  

However, even earlier dates have now been obtained for Monte Verde. Archaeologists carried out spatially-intermittent excavations and core drillings across an area lying between MV-II and the two sites of CH-I and CH-II, located on the south side of the creek, 500 m upstream of MV-II. These revealed stone tools, faunal remains, and evidence of fires widespread across the study area albeit vertically and horizontally discontinuous. These appear to represent ephemeral seasonal activities carried out over a long period of time between shallow channels of a now-buried braided system of streams that fed into the river. Radiocarbon and Optically Stimulated Luminescence dating has yielded a range of dates from 18,500 to 14,500 years ago, with implications that humans reached the New World much earlier than previously believed.

Reference
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Dillehay, T. et al., New Archaeological Evidence for an Early Human Presence at Monte Verde, Chile. PLoS One 10 (11) (2015).
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