Upper Palaeolithic Italy

The early Lower Palaeolithic remains from Ceprano and Monte Poggiolo show that humans arrived in the Italian peninsula sometime prior to 700,000 years ago. However, it is not until the Aurignacian period (~ 38,000-30,000 BP*) of the Upper Palaeolithic that we see signs of widespread occupation. The earliest Aurignacian seems to occur in northern Italy, before expanding southwards (Mussi 1990). The people of the Aurignacian exploited very diverse habitats in both lowland and mountainous areas, as well as on the island of Sicily.

Extrapolating from data by Bocquet-Appel et al. (2005) it is possible that the population of Italy did not exceed 1,000 inhabitants. While this figure is little more than a best guess, it still gives us an idea of the fragile nature of these groups, who were living constantly on the edge of extinction. With such small numbers inbreeding can become a serious problem. However, studies of European Upper Palaeolithic people find them to be surprisingly homogenous as a whole, which would suggest a significant amount of gene flow between far-flung populations (Henke 1989, 1991). In order to understand how mating systems would have operated during the Early Upper Palaeolithic researchers have looked to modern hunter-gatherer groups. Such studies have found hunter-gatherers to have less group closure than agriculturalists. This would have been an important survival strategy for the hunter-gatherer groups of the Upper Palaeolithic, especially when faced with unpredictable environmental conditions and already constrained mating networks. This open network is also reflected in the material culture from this period. Venus figurines, dating chiefly from the Gravettian period, have been found over an area of approximately 2000 km, spanning from modern day Russia in the Northeast to Spain in the Southwest. The Italian Venuses from Savignano, Balzi Rossi and Parabita show the same female form, with an enlarged midsection, pronounced buttocks, large breasts and voluminous thighs, characteristic of the vast majority of these figurines. This suggests that there was an extensive flow of people and ideas during the Early Upper Palaeolithic. This is further supported by the transport of exotic materials, such as flint and shells over distances of several hundred kilometres.

At around 29,000 years ago, the Italian archaeological record falls silent. This hiatus seems to last for around two millennia. Mussi (2000) suggests that Italy may have become a "demographic trap", due to the combination of low population numbers and small group sizes, leading to the eventual extinction of the Aurignacian people.

Based on their assemblages, is believed that the Gravettian people were a new group, who likely entered the Italian peninsula from south-eastern France. As climatic conditions worsen, more exotic artefacts begin to appear in the archaeological record. A major concentration of sites date to around 25,000 BP, suggesting the arrival of immigrants from northern Europe coinciding with the onset of the Last Glacial Maximum. As new people entered Italy, they had to adapt to strange environments and a more limited variety of animals. We no longer find high altitude sites like in the Aurignacian. This shift to lower altitudes is undoubtedly due to the advancing ice. There is evidence of decreased mobility during the Last Glacial Maximum, which continues until the Mesolithic period (Holt 2003). This may reflect a move to more closed systems, as regionalisation grew due to the ever-increasing population density and greater competition over territories. The burial practices, art, and personal adornments of the Early Upper Palaeolithic, which paralleled those from the rest of the continent disappear at the height of the Last Glacial Maximum, further reflecting a shift to more closed social networks. As temperatures begin to improve towards the end of the Last Glacial Maximum, these cultural artefacts reappear in abundance, once again mirroring the styles and practices seen elsewhere in Europe.

Sicily comes in for special attention. The island has long been of interest to anthropologists, who saw the it as a stepping stone between North Africa and Europe. Ferembach (1986) postulated that Sicily may have served as an entry point for the North African Aterians (or their ancestors) around 50,000 years ago, who later became the "Cro-Magnon race". However, this idea finds little archaeological or skeletal support. Evidence of occupation prior to the Last Glacial Maximum in Sicily is patchy at best. At the site of Fontana Nuova, Aurignacian tools and isolated fragments of human bone have been found and estimated to date to around 30,000 years ago, making it the earliest record of occupation for the island (Chilardi et al 1996). However, it is the only evidence we have for the colonisation of the island during the Aurignacian and it is not until the Epigravettian (~20,000-10,000 BP) that we have further evidence of humans in Sicily. This suggests that the earliest settlers probably went extinct due their small numbers, limited resources and restricted gene flow with the mainland. It also reflects the pattern seen in the rest of Italy, since there are no Aurignacian sites known after 30,000 BP.

At the site of Grotta di San Teodoro the skeletal remains of seven individuals were found, making it the single largest Upper Palaeolithic sample in Sicily. An unpublished direct AMS 14C date situates the skeletal remains at around 14,800 BP (D’Amore et al. 2009). A recent craniometric study of the San Teodoro skeletons shows that they have higher affinities with the Late Upper Palaeolithic and Mesolithic populations, rather than Early Upper Palaeolithic ones (ibid.). These results suggest one of two possible scenarios (a) an early arrival with gene flow, thus explaining the homogeneity with the mainland Italian groups or (b) the late arrival of the direct descendants of the San Teodoro population on the island of Sicily. At the time of the Last Glacial Maximum there was probably a land bridge between Sicily and the Italian mainland, with sea levels being some 120 metres lower. The appearance of exotic faunal evidence further suggest this land connection. While Sicily was occupied as early as the Aurignacian, it may not have been until the Late Epigravettian that the island had a stable population able to overcome the threat of extinction. Like the rest of Italy, Sicily gives us a unique insight the challenges faced by Europe’s latest inhabitants.

*BP is used to indicated uncalibrated radiometric years before present.

Bocquet-Appel et al. Estimates of Upper Palaeolithic meta-population size in Europe from archaeological data. Journal of Archaeological Science (2005) vol. 32 (11) pp. 1656-1668.

Chilardi S, Frayer DW, Gioia P, Macchiarelli R, Mussi M (1996) Fontana Nuova di Ragusa (Sicily, Italy): southernmost Aurignacian site in Europe 70: 553-563.

D'Amore G, Marco SD, Tartarelli G, Bigazzi R, Sineo L (2009) Late Pleistocene human evolution in Sicily: comparative morphometric analysis of Grotta di San Teodoro craniofacial remains 56: 537-550.

Ferembach. Les Hommes du Paléolithique Supérieur. Autour du Bassin Méditerraneen. L'Anthropologie (1986) vol. 90 (3) pp. 579-587.

Henke W (1991) Biological Distances in Late Pleistocene and Early Holocene Human Populations in Europe. In: Variability and Evolution. Poznan, Poland: Miskiewicz University Press. pp. 39-64.

Henke (1989) Jungpaläolithiker und Mesolithiker: Beiträge zur Anthropologie. Habilitationsschrift, FB Biologie, Mainz, 1701 S.

Holt BM (2003) Mobility in Upper Paleolithic and Mesolithic Europe: Evidence from the lower limb. Am. J. Phys. Anthropol.

Mussi (1990) Continuity and change in Italy at the Last Glacial Maximum.. In: Soffer, Gamble, editors. The world at 18000: high latitudes. London: . pp. 126-147.

Mussi M (2000) Heading south: the gravettian colonisation of Italy. In: Roebroeks, Mussi, Svoboda, Fennema, editors. Hunters of the Golden Age: The Mid Upper Palaeolithic of Eurasia 30,000–20,000 BP. Leiden: Leiden University Press. pp. 355-374.

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Measuring cranial variation using geography as a proxy for neutral genetic distances

world globe flushing
Certain anatomical features of the human skeleton are known to vary with geography and climate. To what extent each variable contributes to our physical makeup is less clear. The problem is that populations with similar climate are geographically close to one another. Even if we find shared traits among populations from similar climates it may be just as a result of geographic proximity (and thus clinal gene flow), rather than shared common ancestry.

As I mentioned in my previous post, anthropologists often compared cranial data to matched microsatellite datasets. However, it is rarely possible to get an exact match between the cranial and microsatellite populations. The anthropologist will instead use populations that are genetically similar and which may or may not be representative of the target population. Another option is to substitute microsatellite data with geographic distances, since studies have found a strong correlation between genetic distance and geographic distance (Manica et al. 2005; Ramachandran et al. 2005; Romero et al. 2008). This allows us to get around the need to match phenotypic data with genetic datasets.

A recent paper by Betti et al. used geographic distance as a proxy for neutral genetic distance. They set out to test the extent to which cranial differences can be explained by geographic proximity, by comparing pairwise phenotypic distances among populations and pairwise geographic distances using isolation by distance (IBD) models, as well as comparing pairwise cranial distances with climatic variables after correcting for IBD. Geographic distances were calculated as the shortest distance over land between populations while avoiding areas greater than 2000 metres above sea level. Intercontinental land bridges were also factored into their model.

Their study found geographic distance (and by extension genetic distance) to be a strong predictor of cranial variation. Minimum and maximum temperatures were also a significant predictor of cranial differentiation but not as strong as geographic distance. It also appears that much of this climate-related variation is influenced by the populations from exceptionally cold climates. A previous study by Roseman also found that populations living in extremely cold climates showed greater selection. Betti et al. suggest that this may be due to culture acting as an environmental buffer, with the buffer breaking down at extremely cold climates, after which cranial plasticity takes over.

Since climate and geographic distance covary, not considering isolation by distance leads to an overestimation of the effect of climate on cranial differences between populations. Not surprisingly facial traits showed the strongest correlation with climate. In summary, this study suggests that cranial measurements are predominately influenced by neutral evolutionary processes, especially in populations that do not live in extremely cold climates.

Betti et al. 2009. The relative role of drift and selection in shaping the human skull. Am. J. Phys. Anthropol. in press.

Manica A, Prugnolle F, Balloux F. 2005. Geography is a better determinant of human genetic differentiation than ethnicity. Hum Genet 118:366–371.

Ramachandran S, Deshpande O, Roseman CC, Rosenberg NA, Feldman MW, Cavalli-Sforza LL. 2005. Support from the relationship of genetic and geographic distance in human populations for a serial founder effect originating in Africa. Proc Natl Acad Sci USA 102:15942–15947.

Romero IG, Manica A, Goudet J, Handley LL, Balloux F. 2008. How accurate is the current picture of human genetic variation? Heredity 102:120–126.

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Examining cranial robusticity

robust hominin
Palaeoanthropologist Darren Curnoe (2009) gives the following biological definition of the term ‘robust’:

…a descriptive anatomical term referring to individuals, complexes, organs, structures or traits which are heavily built, rugged, well defined or corpulent.

Bones tend to more robust where muscles, tendons or ligaments insert into the periosteum. When these insertion sites are subjected to stress, blood flow increases. This in turn stimulates the production of osteoblasts, which lay down extra bone. With respect to the skull the term robust is generally used to refer to so-called superstructures, such as the supraorbital ridges, occipital crests or zygomaxillary tuberosities. Anthropologists often classify robusticity based on the relative expression of a particular trait, or indeed its absence. Given that robusticity is related to physical stress, traits tend to be more pronounced in males and in certain populations (e.g. Aboriginal Australians and Fuegians).

The retention of robust features in certain populations, particularly Aboriginal Australians, has been used to support the multiregional hypothesis of human origins (e.g. Wolpoff et al. 2001; Frayer et al., 1993). On the other hand, proponents of a replacement model see robust traits (e.g. in Australian Aboriginal populations) as retained plesiomorphies and argue that these traits cannot be used to show continuity (Lieberman 2000). In response, many multiregionalists have revised their position to suggest that the reduction of the browridge in later Neandertals, such as St Césaire and Vindija, represents a synapomorphy between Neandertals and modern humans, likely due to interbreeding. The underlying assumption here is that these robust traits have a strong genetic component. Furthermore, there is a notable decrease in cranial robusticity from the early Upper Palaeolithic to late Upper Palaeolithic. It has been suggested that this may reflect changes in diet. Transition from hunter-gather to agricultural lifestyle is associated with a reduction in cranial robusticity, although correlation does not necessarily prove causation. However, not all hunter-gather groups are universally more robust than argriculturalists, which might suggest some other factors at play.

A recent in press paper by Baab et al. sets out to examine the possible mechanisms behind robust cranial characters. The null hypothesis in their study is that neutral evolutionary processes (e.g. genetic drift) were responsible for the pattern of cranial robusticity in modern humans - the rejection of which would suggest selection acting on these traits. To test the null hypothesis of neutral evolution of cranial robusticity Mahalonobis D2 distances for robust characters were compared to Ddm distances derived from microsatellite data. Microsatellites are useful in reconstructing evolutionary relationships due to their unusually high mutation rates, which result in largely selectively neutral polymorphisms.

Of the variables examined, only cranial shape was significantly correlated with robusticity, while cranial size, climate and neutral genetic distances were not. This is at odds with an earlier study by Mirazón Lahr and Wright (1996) (1996) who found the strongest correlation between cranial robusticity and cranial size. This finding may be due to use of geometric morphometrics by Baab and colleagues, which is better at separating size and shape compared to the linear morphometrics used by Mirazón Lahr and Wright (1996).

Cranial robusticity was not correlated with neutral genetic distances, suggesting that neutral evolutionary processes (e.g. genetic drift) were not responsible for the pattern of cranial robusticity in the populations studied. As noted by the authors, this finding could also be explained by a non-perfect match of populations among some of the cranial and molecular samples. In studies such as this one, it is often difficult to find an exact match between the populations from which we derive our cranial and molecular data. In such cases, we are left with the choice of eliminating samples or using another genetically similar population. The authors choose the latter but neither option is ideal and both have their own disadvantages. Unfortunately, the reason for including Upper Palaeolithic and Neolithic samples in this study is never fully explained and the assumption that modern genetic populations are appropriate proxies for such populations is never justified. Setting this aside, the findings of this study caution the use of robust traits in constructing phylogenetic relationships in modern humans.

The strongest correlations were found between cranial robusticity and either cranial or masticatory shape. This lends support to the hypothesis that robusticity is in some part functionally determined. The study also found crania with more prognathic faces, longer skulls, expanded glabellar and occipital regions to be more robust. Mirazón Lahr and Wright (1996) noted a similar tendency of longer skulls to have superstructures, while further emphasising their tendency to be associated with narrow skulls and a large palatal region.

While most of the robust variables in this study were areas of muscle insertions, the supraorbital region has a distinct aetiology. While many have interpreted the supraorbital region as an area of stress reinforcement in the skull (the so-called beam model) which is strongly influenced by mastication (Endo 1966, 1970; Russell 1985), there is a strong evidence to suggest that this is not its primary purpose. Supraorbital development begins early in life, suggesting that the supraorbital ridge may be part of the overall craniofacial complex and is likely under genetic control. While the beam model is intuitive, it is unsupported by empirical data. Hylander and colleagues (Hylander et al. 1991a, 1991b, 1992; Hylander and Ravosa 1992) conducted in vivo strain gauge experiments in different primates to assess the amount of strain magnitudes generated during mastication. They found these levels to be low to induce bone deposition in all the species they studied, even when chewing hard food. Moreover, anthropoids do not show a correlation between the browridge and the moment arms of the masticatory muscles, as the beam model would predict (Ravosa 1991). These researchers adopt the model proposed by Moss and Young (1960), which views supraorbital development as the result of placement of the brain and eyes. They postulated that the reduction of the brow ridge in modern humans was related to the expansion of the frontal lobe in our species. In hominins with orbits positioned well in front of the frontal lobes, as in chimpanzees or the erectines, the space between the orbits and the brain case is bridged by a brow ridge. If the supraorbital region is under genetic control, as the research of Hylander and Ravosa suggests, it would be of interest to examine this region in isolation to assess if it correlates with neutral evolutionary processes, particularly in light of a recent paper by Von Cramen-Taubedal which found the shape of the frontal bone to be consistent with neutral genetic expectation.


Baab KL, SE Freidline, SL Wang, T Hanson. 2009. Relationship of cranial robusticity to cranial form, geography and climate in Homo sapiens (in press). Am. J. Phys. Anthropol.

Curnoe D. 2009. Possible causes and significance of cranial robusticity among Pleistocene-Early Holocene Australians. Journal of Archaeological Science (2009) vol. 36 (4): 980-990.

Endo B. 1966. Experimental studies on the mechanical significance of the form of the human facial skeleton. J Faculty Sci Univ Tokyo (Section V, Anthropol) 3:1–106.

Endo B. 1970. Analysis of stress around the orbit due to masseter and temporalis muscles respectively. J Anthropol Soc Nippon 78:251–266.

Frayer DW, MH Wolpoff, AG Thorne, FH Smith, GG Pope. Theories of modern human origins: the paleontological test. American Anthropologist (1993) vol. 95 (1): 14-50.

Hylander WL, Picq PG, Johnson KR. 1991a. Masticatory–stress hypotheses and the supraorbital region of primates. Am J Phys Anthropol 86:1–36.

Hylander WL, Picq PG, Johnson KR. 1991b. Function of the supraorbital region of primates. Arch Oral Biol 36:273– 281.

Hylander WL, Ravosa MJ. 1992. An analysis of the supraorbital region of primates: a morphometric and experimental approach. In: Smith P, Tchernov E,
editors. Structure, function and evolution of teeth. Tel Aviv: Freund Publishing. p 223–255.

Lieberman, DE. (2000) Ontogeny, homology, and phylogeny in the Hominid craniofacial skeleton: the problem of the browridge. In P. O'Higgins and M. Cohn (eds.) Development, Growth and Evolution: implications for the study of hominid skeletal evolution. London: Academic Press, pp. 85-122.

Moss ML, RW Young. 1960. A functional approach to craniology. Am. J. Phys. Anthropol. 18:281-292.

Mirazón Lahr M, RVS Wright. 1996. The question of robusticity and the relationship between cranial size and shape in Homo sapiens. Journal of Human Evolution.

Ravosa MJ. 1991. Interspecific perspective on mechanical and nonmechanical models of primate circumorbital morphology. Am J Phys Anthropol. 86(3):369-96.

Russell MD. 1985. The Supraorbital Torus:" A Most Remarkable Peculiarity". Current Anthropology. vol. 26 (3) pp. 337

Wolpoff MH, J Hawks, DW Frayer, K Hunley. 2001. Modern Human Ancestry at the Peripheries: A Test of the Replacement Theory. Science. vol. 291 (5502):293-297.

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Why the Aquatic Ape Hypothesis doesn't hold water

Among this week’s new videos from TED, was a talk given by Elaine Morgan – the chief promoter of the Aquatic Ape Hypothesis (AAH). The AAH was first formulated by Alister Hardy and is the idea that human evolution went through an aquatic stage, which in turn explains many of the features of the human physiology. For anybody with a poor understanding of evolutionary biology the AAH arguments can seem quite compelling. Instead of repeating the numerous reasons why the AAH fails (Jim Moore has an entire website dedicated to this), I wish to address some of the specific arguments made in this video.

Morgan starts off my stating that "… there's one aspect of this story which they [evolutionists] have thrown no light on and they seem anxious to skirt around and step over it and talk about something else. So I'm going to talk about it. It's the question of why are we so different from the chimpanzees?". Either Morgan has not been reading the hundreds of research papers that have addressed these important questions or she is trying to hoodwink her audience. Palaeoanthropologists and primatologists have long recognised the value of studying human and chimp differences in order to understand our shared evolutionary history. In fact, it is impossible to talk about functional anatomy and phylogenetic history in humans without reference to our closest extinct and living hominin relatives.

She continues: "Yet when you look at the phenotypes. There's a chimp, there's a man. They're astoundingly different. No resemblance at all." I am hearing this correctly? No resemblance at all? Even a five year old can see the striking similarities between chimpanzees and humans. To suggest that there is “no resemblance at all” is laughable. It was the similarities of humans to other non-human primates that led Charles Darwin to argue for common ancestry between humans and the great apes. Even without the fossil record and the unambiguous molecular evidence, the morphological similarities alone would be enough to suggest a shared common ancestry of chimps and humans.

Throughout the talk she constantly refers to humans as naked, as if to suggest we are hairless. One need only look at a shirtless Alec Baldwin, Robin Williams or Andy Garcia to know this is not the case. While it is true that humans are less hairy than the rest of our primate kin there are far more compelling hypotheses to explain our lack of hair (thermoregulation, defence against parasites or sexual selection). She claims that hairlessness is an aquatic trait when in fact most aquatic/semi-acquatic mammals are in fact hairy. Otters, polar bears, seals, and walruses are but some examples that spring to mind.

Regarding the failed savannah hypothesis of bipedalism Morgan has this to say: "What do scientists do when a paradigm fails… carry on as though nothing had ever happened… If they haven't got a paradigm they can't ask the questions… The only other option open to them is to stop asking the questions. So that is what they have done now. That is why you don't hear them talking about it."

When paradigms fail science marches on. When was the last time you heard a scientist defending the merits of Lamarckism, psychoanalysis and phrenology? Morgan is correct that the savannah hypothesis doesn’t weigh up against the evidence but she mistakenly claims that the anthropologists haven’t let go of this idea. The savannah hypothesis was formulated in a time when there was a dearth of palaeoecological data for the most important African archaeological sites. As more data came in, anthropologists changed their models correspondingly. No serious anthropologist still adheres to the savannah hypothesis. Morgan chooses to ignore this fact, instead preferring the easier route of attacking a strawman. In the references section below, you will find just a spattering of the work anthropologists have been doing on palaeoecological reconstructions of the environments occupied by our forebearers. These papers address the very questions Morgan asserts that scientists have stopped asking. Does she not read the anthropological literature or does she just choose to ignore it? She implies that because the savannah hypothesis is false it somehow offers support to the AAH. In fact, the consensus opinion suggests that neither savannah nor aquatic environments were very important in the early stages of human evolution, but rather our hominin ancestors exploited wood and forest habitats. A number of anthropologists have proposed an arboreal origin of hominin bipedality (Crompton 2008; Pickerford 2006; Senut 2003, 2006). In fact, the best known human ancestor Lucy shows clear arboreal adaptations.

Morgans proceeds by stating that "there is only one circumstance in which they always, all of them [non human primates], walk on two legs and that is when they are wading through water." Contrary to Morgan’s claim, the data have shown apes to be bipedal more often on land than in the water.

She follows this up by saying that the fat in humans is similar to that seen in aquatic mammals. Humans have a similar number of fat cells compared with other primates. The increased subcutaneous fat seen in humans is most likely a result of diet rather than an evolutionary adaptation. Non-human primate obesity is well documented, particularly in primates kept in captivity (Videan 2007; Altmann et al 1993; Kemnitz et al 1989; Schwartz et al 1993). Moreover, the distribution of fat in humans runs contrary to need aquatic mammals have for streamlining.

Ten minutes into the talk she states that "the only creatures that have got conscious control of their breath are the diving animals and the birds". Humans are not the only non-aquatic mammal which can hold its breath. Various monkeys, for instance, can and do hold their breath, as well as dogs.

Finally, she asserts that "we are streamlined." Humans are anything but streamlined. Our motion in the water is generally quite wasteful. Ask any swimming coach. Fish have a fusiform shape (tapered at both ends), which is ideal for moving through the water with the least amount of resistance. Let’s put this into perspective. The sailfish records speeds of up to 116 km/hr (72 mph), while Michael Phelps can average a measly about 6.5 km/hr (4 mph) on a good day! Our body shape is a consequence of our adaptation to bipedalism, the requirements of childbirth in women, sexual dimorphism and sexual selection.

While I generally enjoy listening to the speakers at TED, I think this is an idea NOT worth spreading.


Altmann J, Alberts SC, Altmann SA, Roy SB (2002) Dramatic change in local climate patterns in the Amboseli Basin, Kenya. Afr J Ecol 40, 248–251.

Altmann J, Schoeller D, Altmann SA, Muruthi P, Sapolsky RM (1993) Body size and fatness of free-living baboons reflect food availability and activity levels. Am J Primatol 30: 149–61.

Andrews P (1996) Palaeoecology and hominoid palaeoenviron-ments. Biol Rev 71, 257–300.

Andrews P, Humphrey L (1999) African Miocene environments and the transition to early hominines. In African Biogeography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 282–300. New York: Oxford University Press.

Andrews P (2007) The biogeography of hominid evolution. J Biogeogr 34, 381–382.

Andrews P, Kelley J (2007) Middle Miocene dispersals of apes. Folia Primatol 78, 328–343.

Andrews P, Bamford M (2008) Past and present vegetation ecology of Laetoli, Tanzania. J Hum Evol 54, 78–98.

Codron D, Luyt J, Lee-Thorp JA, Sponheimer M, De Ruiter D, Codron J (2005) Utilization Of Savanna-Based Resources By Plio-Pleistocene Baboons. S Afr J Sci 101, 245–248.

Crompton RH, EE Vereecke, SKS Thorpe (2008) Locomotion and posture from the common hominoid ancestor to fully modern hominins, with special reference to the last common panin/hominin ancestor. J Anat 212, 501–543.

Demenocal PB (2004) African Climate Change And Faunal Evolution During The Pliocene-Pleistocene. Earth Planet Sci Lett 220, 3–24.

Denton G (1999) Cenozoic climate change. In African Biogeography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 94–114. New York: Oxford University Press.

Dowsett HJ, Barron JA, Poore RZ, et al. (1999) Middle Pliocene paleoenvironmental reconstruction: PRISM2. US Geol Surv, Reston, Va, Open File Rep 99–535.

Elton S (2000) Ecomorphology and evolutionary biology of African Cercopithecoids: providing an ecological context for hominin evolution. PhD dissertation, University of Cambridge.

Jacobs BF (2004) Palaeobotanical studies from tropical Africa: relevance to the evolution of forest, woodland and savannah biomes. Phil Trans R Soc Lond B359, 1573–1583.

Kemnitz JW, Goy RW, Flitsch TJ, Lohmiller JJ, Robinson JA (1989) Obesity in male and female rhesus monkeys: fat distribution, glucoregulation, and serum androgen levels. J Clin Endocrinol Metab 69:287–93.

Kingston J, Harrison T (2007) Isotopic dietary reconstructions of Pliocene herbivores at Laetoli: implications for hominin paleo- ecology. Palaeogeog Palaeoclimatol Palaeoecol 243, 272–306.

Kovarovic KM, Andrews P, Aiello L (2002). The palaeoecology of the Upper Ndolanya Beds, Laetoli, Tanzania. J Hum Evol 43, 395–418.

Pickford M (2006) Paleoenvironments, Paleoecology, Adaptations and the Origins of Bipedalism in Hominidae. In Human Origins and Environmental Backgrounds (eds Ishida H, Tuttle RH, Pick- ford M, Ogihara M, Nakatsukasa M), pp. 175–198. Heidelberg: Springer.

Schwartz SM, Kemnitz JW, Howard CF Jr (1993) Obesity in free-ranging rhesus macaques. Int J Obes 17:1–9.

Senut B (2003) Palaeontological approach to the evolution of hominid bipedalism: the evidence revisited. Cour Forsch-Inst Senkenberg 243, 125–134.

Senut B (2006) Arboreal Origins of Bipedalism. In Human Origins and Environmental Backgrounds (eds Ishida H, Tuttle RH, Pickford M, Ogihara N, Nakatsukasa M), pp. 199–208. Heidelberg: Springer.

Sikes N (1999) Plio-Pleistocene floral context and habitat prefer- ences of sympatric hominid species in East Africa. In African Bio- geography, Climate Change and Early Hominid Evolution (eds Bromage TG, Schrenk F), pp. 301–315. New York: Oxford Univer- sity Press.

Videan EN, J Fritz, J Murphy (2007) Development of guidelines for assessing obesity in captive chimpanzees (Pan troglodytes). Zoo Biology 26: 93–104.

Vincens A, Garcin Y, Buchet G. (2007) Influence of rainfall seasonality on African lowland vegetation during the Late Quaternary: pollen evidence from Lake Masoko, Tanzania. J Biogeogr 34, 1274–1288.

WoldeGabriel G, Haile-Selassie Y, Renne P, et al. (2001) Geology and palaeontology of the Late Miocene Middle Awash valley, Afar rift, Ethiopia. Nature 412, 175–178.

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Beware the Spinal Trap

Bristol Spine
Today, numerous blogs and magazines from all around the world will publish Simon Singh’s article on chiropractic from April 2008, with the libellous part removed. The Guardian withdrew the article after the British Chiropractic Association sued for libel (please repost).


Some practitioners claim it is a cure-all, but the research suggests chiropractic therapy has mixed results – and can even be lethal, says Simon Singh.

You might be surprised to know that the founder of chiropractic therapy, Daniel David Palmer, wrote that “99% of all diseases are caused by displaced vertebrae”. In the 1860s, Palmer began to develop his theory that the spine was involved in almost every illness because the spinal cord connects the brain to the rest of the body. Therefore any misalignment could cause a problem in distant parts of the body.

In fact, Palmer’s first chiropractic intervention supposedly cured a man who had been profoundly deaf for 17 years. His second treatment was equally strange, because he claimed that he treated a patient with heart trouble by correcting a displaced vertebra.

You might think that modern chiropractors restrict themselves to treating back problems, but in fact some still possess quite wacky ideas. The fundamentalists argue that they can cure anything, including helping treat children with colic, sleeping and feeding problems, frequent ear infections, asthma and prolonged crying – even though there is not a jot of evidence.

I can confidently label these assertions as utter nonsense because I have co-authored a book about alternative medicine with the world’s first professor of complementary medicine, Edzard Ernst. He learned chiropractic techniques himself and used them as a doctor. This is when he began to see the need for some critical evaluation. Among other projects, he examined the evidence from 70 trials exploring the benefits of chiropractic therapy in conditions unrelated to the back. He found no evidence to suggest that chiropractors could treat any such conditions.

But what about chiropractic in the context of treating back problems? Manipulating the spine can cure some problems, but results are mixed. To be fair, conventional approaches, such as physiotherapy, also struggle to treat back problems with any consistency. Nevertheless, conventional therapy is still preferable because of the serious dangers associated with chiropractic.

In 2001, a systematic review of five studies revealed that roughly half of all chiropractic patients experience temporary adverse effects, such as pain, numbness, stiffness, dizziness and headaches. These are relatively minor effects, but the frequency is very high, and this has to be weighed against the limited benefit offered by chiropractors.

More worryingly, the hallmark technique of the chiropractor, known as high-velocity, low-amplitude thrust, carries much more significant risks. This involves pushing joints beyond their natural range of motion by applying a short, sharp force. Although this is a safe procedure for most patients, others can suffer dislocations and fractures.

Worse still, manipulation of the neck can damage the vertebral arteries, which supply blood to the brain. So-called vertebral dissection can ultimately cut off the blood supply, which in turn can lead to a stroke and even death. Because there is usually a delay between the vertebral dissection and the blockage of blood to the brain, the link between chiropractic and strokes went unnoticed for many years. Recently, however, it has been possible to identify cases where spinal manipulation has certainly been the cause of vertebral dissection.

Laurie Mathiason was a 20-year-old Canadian waitress who visited a chiropractor 21 times between 1997 and 1998 to relieve her low-back pain. On her penultimate visit she complained of stiffness in her neck. That evening she began dropping plates at the restaurant, so she returned to the chiropractor. As the chiropractor manipulated her neck, Mathiason began to cry, her eyes started to roll, she foamed at the mouth and her body began to convulse. She was rushed to hospital, slipped into a coma and died three days later. At the inquest, the coroner declared: “Laurie died of a ruptured vertebral artery, which occurred in association with a chiropractic manipulation of the neck.”

This case is not unique. In Canada alone there have been several other women who have died after receiving chiropractic therapy, and Edzard Ernst has identified about 700 cases of serious complications among the medical literature. This should be a major concern for health officials, particularly as under-reporting will mean that the actual number of cases is much higher.

If spinal manipulation were a drug with such serious adverse effects and so little demonstrable benefit, then it would almost certainly have been taken off the market.

Simon Singh is a science writer in London and the co-author, with Edzard Ernst, of Trick or Treatment? Alternative Medicine on Trial.

You can find this article and information about Simon Singh’s case at the Sense About Science website, as well as a petition to keep libel laws out of science.

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The impact of cranial plasticity on the reconstruction of human population history

Palaeoanthropologists are interested in reconstructing the evolutionary history of our species from fossil remains. Like other taxonomists they are primarily interested in identifying shared derived traits, otherwise known as synapomorphies. A synapomorphic trait is shared by some members of a taxa and not by others, since the former inherited this trait from a common ancestor. For instance, the retention of a clavicle (collar bone) is one of the more cited synapomorphic traits common to all primates.

A homoplasy is a trait that is present in two or more taxa but that has not been derived through common ancestry but rather through convergence, parallelism, or reversal. The wings of insects, birds and bats are homoplasies, since they arose through convergent evolution. Thus, homoplasies and synapomorphies may be identical in appearance but are distinguished by whether or not they arose through common ancestry. As a result, it can often difficult to pry apart traits which are synapomorphies from those which are homoplasies. A subset of homoplasies are termed homoiologies. Lycett and Collard (2005) define homoiologies as:

“… phylogenetically misleading resemblances among a group of taxa that can be ascribed to phenotypic plasticity. That is, homoiologies are homoplasies that result from the expression by a genotype of different phenotypes in response to different environmental conditions.”

They arise primarily from nonheritable epigenetic responses to mechanical stimuli. The "homoiology hypothesis" (Lieberman 1995) was derived from the well known fact that bone shape and size can be modified by mechanical loading. As such, homoiologies are expected to have greater influence upon the more plastic regions of a phenotype.

The homoiology hypothesis makes two testable predictions:

1. Traits subject to biomechanical stress should exhibit higher within-taxon variability due to the increased plasticity.

2. These traits should be less reliable for reconstructing phylogeny.

Previous studies have examined the homoiology hypothesis in various primate species (Collard and Wood 2007, 2000). These studies found that the regions of the skull associated with mastication indeed exhibited higher within-taxon variability but they were as reliable in reconstructing phylogenetic relationships as other regions of cranium not directly associated with masticatory function. Since these studies looked at interspecific studies, it was suggested that maybe homoiology was a greater problem for intraspecific studies.

A paper (in press) in the Journal of Human Evolution by Noreen von Cramon-Taubadel tests the homoiology hypothesis in an intraspecific study of human populations. Areas of the skull related with mastication would be expected to be under greater biomechanical stress, and as such be more affected by homoiology. She divided the skull into zones thought to be related to mastication (zygotemporal and palatomaxilla regions) and zones relatively unaffected by mastication (the upper face, cranial vault and basicranium). She tested the predictions of the homoiology hypothesis by comparing craniometric data with matched molecular data for 12 modern human populations.

Like previous interspecific studies, regions of the skull related to mastication show great variability (as predicted by the homoiology hypothesis) but these regions were no less reliable at reconstructing phylogenies (at variance with the homoiology hypothesis). It is worth noting that if biomechanical stress affects all individuals in the same way then these characters will not confound the phylogenetic analysis.

These findings mean that the homoiology hypothesis is flawed in at least some of its premises. The results of this and previous studies suggest that within-taxon variability should not be used to assertion the usefulness of cranial traits for determining phylogenetic relationships. Moreover, it does not appear to hold that homoiologies are any more problematic in determining intraspecific evolutionary relationships as interspecific ones. Finally, even though regions of the skull related to mastication are more variable than non-masticatory regions, they do not seem to be any less reliable for the reconstruction of phylogenies.

Collard and Wood. Hominin homoiology: An assessment of the impact of phenotypic plasticity on phylogenetic analyses of humans and their fossil relatives. Journal of human evolution (2007) vol. 52 (5) pp. 573-584.

Collard and Wood. How reliable are human phylogenetic hypotheses?. Proc. Natl. Acad. Sci. U.S.A. (2000) vol. 97 (9) pp. 5003-6.

Cramon-Taubadel. Revisiting the homoiology hypothesis: the impact of phenotypic plasticity on the reconstruction of human population history from craniometric data. Journal of Human Evolution (2009) pp. 1-12.

Lieberman. Testing hypotheses about recent human evolution from skulls: integrating morphology, function, development, and phylogeny. Curr. Anthropol. (1995) 36, 159–197.

Lycett and Collard. Do homoiologies impede phylogenetic analyses of the fossil hominids? An assessment based on extant papionin craniodental morphology. Journal of human evolution (2005) vol. 49 (5) pp. 618-642.

Wood and Lieberman. Craniodental variation in Paranthropus boisei: a developmental and functional perspective. American Journal of Physical Anthropology (2001) vol. 116 (1) pp. 13-25.

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Who made the Aurignacian?

Until recently, it was largely assumed that the Aurignacian was contemporaneous with the arrival of anatomically modern humans in Europe sometime around 40,000 years ago. This industrial complex is named after the site of Aurignac in southern France and is found throughout Europe and southwest Asia. The evidence for an association between modern humans the Aurignacian has been less than clear cut.

For most of the last century, the prevalent view among archaeologists was that Neandertals only made Mousterian tools. However, the discovery of the St Césaire 1 Neandertal skeleton and the Neandertal remains from Arcy-sur-Cure with Châtelperronian industry put paid to this idea. Châtelperronian tools show a mix of features otherwise found in the Mousterian and Aurignacian industries. What was particularly surprising about the Châtelperronian culture was not only the lithics but also the manufacture of bone tools and personal ornaments. At the site of Arcy-sur-Cure archaeologists found pierced teeth, ivory, shell, and bone in the Châtelperronian layers. The Szeletian industry of central Europe and the Uluzzian industry of Italy may also be related to the Châtelperronian.

The Châtelperronian has shown that Neandertals were more skilful than previously thought and has opened up the possibility that they may have been the authors of the Aurignacian. At Vindija Cave in Croatia Neandertal remains were speculated to be associated with an Aurignacian-like assemblage (Smith et al. 1999). The skeletal fragments from this site show clear Neandertal affinities. However, problems with stratigraphic control during excavations, as well as evidence of cryoturbation and bioturbation mean that the Neandertal-Aurignacian association is questionable.

However, many of the best associations of the Aurignacian with modern humans are equally problematic. At Bacho Kiro Cave in Bulgaria a "proto-Aurignacian" culture has been associated with some fragmentary human remains (Kozłowski 1982). However, dates from the "proto-Aurignacian" layer span over thousands of years suggesting (1) a very long accumulation of sediment, (2) contamination or (3) incorrect context. Moreover, the fragmentary nature of the remains has meant that a taxonomic diagnosis is difficult.

Human remains were found at the Aurignacian levels of the Spanish site of El Castillo. Unfortunately, the remains were later lost before a detailed anatomical description could be published. A subsequent assessment by Garralda of available descriptions (1989) suggests that the remains were robust, a trait common to both Neandertals and early modern humans. Other sites such as Hahnöfersand and Vogelherd (Street et al. 2006), once thought to date to the Aurignacian have since been dramatically redated to more recent periods.

Evidence of a modern human-Aurignacian association are somewhat better at the sites of Zlatý kůň in the Czech Republic and Kent's Cavern in England. Perhaps, the best evidence we have comes from the site of Mladeç in the Czech Republic. Bone points, perforated animal teeth and a few lithics have been found there. The assemblage appears to be Aurignacian and is associated with skeletal remains that have been well dated to around 31,000 radiocarbon years.

A recent study by Bailey et al. (2009) attempts to shed further light on the makers of the Aurignacian. Many Aurignacian sites have dental remains but they largely have not been used in taxonomic identification. The authors of this paper use Bayesian statistics to classify individual based on the teeth. They used teeth samples for which taxonomy was known to test the accuracy of their technique. In cross validation of known samples, 89% of both Neandertals and modern humans were correctly classified. In the subsequent analysis of the 34 unknown samples associated with Upper Palaeolithic industries, 29 were assigned to modern humans. This is perhaps the strongest evidence to date that modern humans made the Aurignacian. However, this study cannot completely rule out the possibility that Neandertals could have been responsible, albeit for in small part, for the Aurignacian.

Bailey SE, Weaver TD, Hublin J-J. 2009. Who made the Aurignacian and other Upper Paleolithic industries? Journal of Human Evolution.

Garralda MD. 1989. Upper Paleolithic human remains from El Castillo Cave (Santander, Spain). In: Giacobini G, editor. Hominidae: Proceedings of the 2nd International Congress of Human Paleontology. Turin: Jaca Book. pp. 479-482.

Kozłowski JK. 1982. Excavation in the Bacho Kiro Cave (Bulgaria): final report. Warsaw: Panstwowe Wydawnictwo Naukowe.

Smith FH, Trinkaus E, Pettitt PB, Karavanić I, Paunović M. 1999. Direct radiocarbon dates for Vindija G1 and Velika Pećina late Pleistocene hominid remains. Proc Natl Acad Sci USA 96.

Street M, Terberger T, Orschiedt J. 2006. A critical review of the German Paleolithic hominin record. Journal of Human Evolution 51(6).

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The origin of bone words


Comes from a Latin word meaning a correct mixture or balance in the sense of tempering a metal. It later came to mean a mental balance. It is related to the word temper which we have come to associate with its negative sense, i.e. to lose one's temper.

Sphenoid: Many bones are named for their shape like this one which comes from the Greek sphēnoeidēs meaning wedge-like.

Orbit: The Latin word orbis had the meaning of round or spherical and referred to the shape of the eye sockets.

Nasal: Latin nasus meaning nose.

Nasal concha: Concha is the latin word for a shell or mollusk.

Vomer: This word means ploughshare or stylus in Latin and the bone is so named for its shape.

Lacrimal/Lacrymal: This bone, located in the eye socket, gets its name from the Latin word for tear, lacrima.

Ethmoid: From the Greek word ēthmos meaning sieve.

Zygomatic: Related to the Greek word zugon which mean yoke.

Palatine: The Latin word palatum has the meaning palate or sense of taste.

Hyoid: Named for its shape, this bone was thought to resemble the letter upsilon "υ" in Greek and in fact the word huoeidēs means upsilon-like.

Axial Skeleton

Scapula: Comes from the Latin scapulae "shoulder blades", which in turn is related to the Greek skaphein meaning to "to dig out". It is possible that the shoulder blades were used as digging tools in times past.

Clavicle: The Latin word clavicula has the meaning of small key, the diminutive form of clavis (so called because of its shape). It is a loan word from the Greek kleis which means "key, collarbone."

Rib: Has its roots in the Old English rib, and ribb of Germanic origin and further related to Dutch rib(be) as well as the German Rippe with the meaning of "a covering", from the Proto Indo European root rebh- meaning "roof."

Vertebra: Comes from the Latin vertebra meaning "joint or articulation of the body, joint of the spine", probably from vertere meaning "to turn" with the -bra suffix relating to the arms.

Manubrium: Come from the Latin manus (hand) with the meaning of handle or haft.

Sternum: Came to English through Latin via the Greek word for chest sternon.

Sacrum: From the Latin os sacrum, which itself is a translation of Greek hieron osteon "sacred bone." This name may originate from the fact that the sacrum was often offered up as part of animal sacrifices.

Innominate: Comes from Latin innominatus meaning "nameless."

Pelvis: Has its roots in the Latin word pelvis meaning "basin" (Old Latin peluis), and ultimately from the Proto Indo European root pel- meaning "container."

Arm Bones

Humerus: Related to the Latin word for the upper arm or shoulder umerus.
Its roots have been traced to the Proto Indo European *omesos and to the Sanskrit amsah and Greek omos.

Radius: This word comes to English from Latin and as you may have guessed has something to do with the radius of a circle. The meaning was literally spoke (of a wheel, etc.) or ray.

Ulna: Although the relationship may not be apparent at first glance the words ulna and elbow are etymologically related. The Old English word eln shares an Indo-European root with the Latin ulna. The Old English word for elbow was elnboga which is broken down into eln "forearm" and boga "bend, bow." There is a older Proto Indo-European root *el- meaning "forearm, elbow."

Hand Bones

Scaphoid: Comes from two Greek words eidos or εἶδος meaning “like” or “resembling” and skaphe or σκάφη meaning a boat.

Lunate: From the Latin word lunaris meaning moon. Named for its crescent moon shape.

Triquetral: From Latin triquetrus meaning “three-cornered” or “triangular”.

Pisiform: Named for its resemblance (Latin: forma = shape) to a pea (Latin: pīsum).

Trapezium: Named for its trapezoidal shape. The Greek word trapeza meant “table” and is itself derived from two root words tra- “four” and peza “foot”. The latter word is related to the -pus in octopus and -ped in pedestrian and pedometer.

Trapezoid: See trapezium. Literally table (Greek: trapeza) shaped (Greek: eidos or εἶδος).

Capitate: From the Latin caput meaning “head”.

Hamate: Latin hamatus, from hamus meaning “hook”.

Leg Bones

Femur: Comes from the Latin word femur meaning thighbone.

Tibia: The same word in Latin was used for the shinbone but also had the meaning of "pipe" or "flute," presumably because of it's shape.

Fibula: Comes from the Latin word fibula, which meant "clasp, buckle, brooch" probably because its shape resembled that of a fastener. Etymonline suggests that it is probable related to the Greek perone, which had this meaning. On the other hand, the Oxford English Dictionary points to a possible relationship with the Latin figere meaning "to fix," which in turn can be traced back to a PIE root *dhigw- ("to stick, to fix").

Foot Bones

Calcaneus: Comes from the Latin calx, meaning heel as well as chalk. This in turn derives from the Greek χάλιξ meaning pebble or stone.

Talus: From the Latin talus meaning ankle. It is related to the Latin word taxillus, which was a small die, since dice were originally made from the anklebones of animals.

Navicular: Related to the English word navy. This bone was so named because of its similarity to a boat (navicula in Latin).

Cuneiform: From the Latin cuneus meaning “wedge”.

Cuboid: Named for its square shape.

Last Updated: 29 May, 2009

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Darwinism: The creationist straw man

If you visit the ironically entitled creationist website Evolution News and Views, try finding a single post that doesn't mention the word “Darwinist” or “Darwinism”. You’ll have to dig deep… very deep. If you were completely ignorant of biology you might even be fooled into thinking that these were terms cheerfully embraced by the scientific community. After all, an evolution news outlet is hardly in the business of obfuscation, now is it?

Outside of intelligent design (i.e., creationism warmed-over), Darwinism is used primarily to refer to the theory of the evolution of species by natural selection, as formulated by Darwin, not to the modern and more complete understanding of evolution. As things tend to be in science, evolutionary theory hasn’t stood still since 1859, when Darwin communicated his ideas to the world in On the origins of species. While natural selection is indeed a principle driving force in evolution, it is not the whole story. Charles Darwin would no doubt be astonished by the such discoveries of genes and DNA, the reworking of evolutionary theory to accommodate evo-devo and the neutral theory of molecular evolution, as well as the plethora of evidence that has confirmed the basic tenets of his original ideas. To use the term Darwinism is an insult to the hard work of the thousands of scientists who have helped refine evolutionary theory. It implies that the wheels of scientific research ground to a halt some 150 years ago and serves to confuse the public’s already poor understanding of evolution.

A more menacing motivation for using the term Darwinism is to portray evolution as just another ideology, consisting of its own set of monolithic doctrines and beliefs. However, science is not based on static beliefs but is rather a ceaselessly self-correcting discipline that evolves in light of new evidence.

By misrepresenting evolution as the archaic, dogmatic ideas of one old man, creationists set up a straw man argument. It always strikes me as curious that they don’t refer to adherents of gravity as Newtonists! Judging from the overwhelming and ever-increasing evidence for evolution, creationists are given little choice but to resort to fallacious arguments.

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Argumentum ad hominem

As I noted in an earlier post, this blog was partly named as a misspelt pun on the ad hominem argument. Argumentum ad hominem (Latin: "argument to the man") involves attacking the character or circumstances of one's opponent in order to undermine them, instead of addressing the substance of their argument. Ad hominem arguments are generally regarded as fallacious, since they do not address the opponent’s argument itself.

This argument comes in the following forms:

The tactic is to portray the opponent as a bad or immoral person, and conclude based on this, that their argument should not be accepted, e.g.

Ann says that anthropological research needs more funding. This is coming from a woman who divorced her husband.

Involves suggesting that the person making the argument is so doing out of self interest, e.g.

She's an anthropologist. Of course, she's going to say that evolution is true.

Tu quoque (Latin: "you too")
This is commonly heard in political debates. Also referred to as the "hypocrisy argument" or the “you too fallacy”, it involves showing that the opponent's arguments or criticisms apply or have applied to them, e.g.

You said Neandertals and modern humans interbreed but only last year you said that they didn't.

Poisoning the well
Is a pre-emptive attack meant to discredit one's opponent before they even make their argument, e.g.

Darwinists have been preaching the evolution lie for years. I suspect that tonight's debate won't be any different.

Guilt by association
Is the view that an individual shares the qualities of others based on irrelevant associations, e.g.

Craniometrics was used in the early twenthieth century to promote eugenics. Anthropologists who carry out craniometric analyses are like Nazis.

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