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ScienceWeek
2004 25 June C6 6. ANTHROPOLOGY: SHELL BEADS AND THE EMERGENCE OF HUMAN BEHAVIOR
The following points are made by C. Henshilwood et al (Science 2004 304:404):
1) There are two competing models for the emergence of modern human behavior: first, a late emergence in Africa or Eurasia at 50,000 to 40,000 years ago (ka), and second, a gradual transition in Africa between 250 to 50 ka (1). In both models, personal ornaments and art are unquestioned expressions of symbolism that equate with modern human behavior. The earliest undisputed African personal ornaments are 13 ostrich eggshell beads from Enkapune Ya Muto in Kenya at 40 ka (2). Evidence from Eurasia includes two perforated teeth, dated 43 ka, from Bacho Kiro in Bulgaria and 58 marine shell beads from the 41-ka layers of Žaizli, Turkey (3).
2) The authors report on 41 perforated tick shell (Nassarius kraussianus) beads recovered from the Middle Stone Age (MSA) levels at Blombos Cave, a site located on the southern Cape shoreline of the Indian Ocean (4). Phase M1, in which 39 beads were found, was dated to 75.6 +- 3.4 ka, by optically stimulated luminescence (OSL) signals from both single aliquots and 4800 individual quartz grains. Thermoluminescence dates for five burnt lithic samples from the same phase provide a mean age of 77 +- 6 ka (5). Two beads that may be intrusive come from the top of the underlying, and still undated, phase M2.
3) The MSA tick shells cannot derive from the cave walls, are too small to be leftovers from human food, and were not brought to the site accidentally by animals, because their only known predator is a gastropod (Natica tecta) that lives, like N. kraussianus, only in estuarine environments. If the tick shells had been accidentally brought to the cave site from 20-km-distant estuaries in wracks of dead Zostera capensis, a grass used for bedding by Later Stone Age (LSA) hunter-gatherers, all age classes would have been present, whereas Blombos Cave MSA beads include shells of adults only.
4) Of the MSA tick shells, 88% are dorsally perforated near the lip. This type of perforation is absent in living populations and accounts for only 8.6% of naturally pierced shells in modern thanatocoenoses. Microscopic analysis of the MSA shells reveals a use-wear pattern, absent on natural shells, consisting of facets that flatten the outer lip or create a concave surface on the lip close to the anterior canal. A similar concave facet is seen opposite to the first one, on the parietal wall of the aperture of many of the shells. This use-wear pattern is consistent with friction from rubbing against thread, clothes, or other beads and is the principal factor that defines the MSA shells as beads. Microscopic residues of ochre detected inside the shells suggest that either the material in contact with the beads or the beads themselves were colored red.
References (abridged):
1. F. d'Errico, Evol. Anthropol. 12, 188 (2003)
2. S. H. Ambrose, J. Archaeol. Sci. 25, 377 (1998)
3. S. Kuhn et al., Proc. Natl. Acad. Sci. U.S.A. 98, 7641 (2001)
4. C. S. Henshilwood et al., J. Archaeol. Sci. 28, 421 (2001)
5. C. S. Henshilwood et al., Science 295, 1278 (2002)
Science http://www.sciencemag.org
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ANTHROPOLOGY: ORIGIN OF CLOTHING: MOLECULAR EVIDENCE
The following points are made by R. Kittler et al (Current Biology 2003 13:1414):
1) The human head louse (Pediculus humanus capitis) and body louse (P. humanus corporis or P. h. humanus) are strict, obligate human ectoparasites that differ mainly in their habitat on the host: the head louse lives and feeds exclusively on the scalp, whereas the body louse feeds on the body but lives in clothing. This ecological differentiation probably arose when humans adopted frequent use of clothing, an important event in human evolution for which there is no direct archaeological evidence.
2) The authors used a molecular clock approach to date the origin of body lice, assuming that this should correspond with the frequent use of clothing. Sequences were obtained from two mtDNA and two nuclear DNA segments from a global sample of 40 head and body lice, and from a chimpanzee louse to use as an outgroup.
3) The results indicate greater diversity in African than non-African lice, suggesting an African origin of human lice. A molecular clock analysis indicates that body lice originated not more than about 72,000 +- 42,000 years ago; the mtDNA sequences also indicate a demographic expansion of body lice that correlates with the spread of modern humans out of Africa. The authors suggest these results indicate that clothing was a surprisingly recent innovation in human evolution.
4) The authors point out that a critical assumption is that the origin of body lice reflects the origin of clothing; it is possible that clothing existed for some time before lice exploited this new ecological niche, in which case the origin of clothing could be much more ancient than the origin of body lice. While the authors cannot exclude this possibility, the colonization of a new ecological niche usually occurs rapidly after it becomes available. Since modern humans and archaic humans such as Neandertals diverged approximately 250,000 to 500,000 years ago, in order to associate clothing with archaic humans, clothing would have had to exist for hundreds of thousands of years before the origin of body lice, which seems improbable. Moreover, archaeological evidence does not contradict an association of clothing specifically with modern humans, as the only tools that can be definitely associated with clothing, such as needles, are only approximately 40,000 years old. Earlier tools, such as scrapers, may have been used to prepare hides for clothing, but may also have been used to scrape flesh for food or some other purpose. Indeed, clothing may have allowed early modern humans to colonize more extreme latitudes than their archaic predecessors, and hence might have been a factor in the successful spread of modern humans out of Africa.
Current Biology http://www.current-biology.com
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ANTHROPOLOGY: NEW EVIDENCE FOR OUT OF AFRICA MODEL
The following points are made by Chris Stringer (Nature 2003 423:692):
1) The idea that modern humans originated in Africa, with populations subsequently spreading outwards from there, has continued to gain support lately. But much of that support has come from analyses of genetic variation in people today, and from fossil and archaeological discoveries dated to within the past 120,000 years -- after our species evolved. Hard evidence for the inferred African origin of modern humans has remained somewhat elusive, with relevant material being fragmentary, morphologically ambiguous, or uncertainly dated. Thus the fossilized partial skulls from Ethiopia recently described by White et al (Nature 2003 423:742) are probably some of the most significant discoveries of early Homo sapiens so far, owing to their completeness and well-established antiquity of approximately 160,000 years.
2) There are two broad theories about the origins of H. sapiens. A few researchers still support a version of the "multiregional" hypothesis, arguing that the anatomical features of modern humans arose in geographically widespread hominid populations throughout the Pleistocene epoch (which lasted from around 1.8 million to some 12,000 years ago). But most researchers now espouse a version of the "out of Africa" model, although there are differences of opinion over the complexity of the processes of origin and dispersal, and over the amount of mixing that might subsequently have occurred with archaic (non-modern) humans outside of Africa. Within Africa, uncertainties still surround the mode of modern human evolution -- whether it proceeded in a gradual and steady manner or in fits and starts (punctuational evolution). Other questions concern the relationship between genetic, morphological and behavioral changes, and the precise region, or regions, of origin.
3) For instance, possible early H. sapiens fossils, dating from about 260,000 to 130,000 years ago, are scattered across Africa at sites such as Florisbad (South Africa), Ngaloba (Tanzania), Eliye Springs and Guomde (Kenya), Omo Kibish (Ethiopia), Singa (Sudan) and Jebel Irhoud (Morocco). But the best dated of these finds, from Florisbad and Singa, are problematic because of incompleteness and, in the latter case, evidence of disease. Meanwhile, the more complete or diagnostically modern specimens suffer from chronological uncertainties. So the most securely dated and complete early fossils that unequivocally share an anatomical pattern with today's H. sapiens are actually from Israel, rather than Africa. These are the partial skeletons from Skhul and Qafzeh, dating from around 115,000 years ago. Their presence in the Levant is usually explained by a range expansion from ancestral African populations, such as those sampled at Omo Kibish or Jebel Irhoud around 125,000 years ago.
4) The new cranial material from Herto, Ethiopia -- described by White et al -- adds significantly to our understanding of early H. sapiens evolution in Africa. The fossils are complete enough to show a suite of modern human characters, and are well constrained by argon-isotope dating to about 160,000 years ago. Three individuals are represented by separate fossils: a nearly complete adult cranium (skull parts excluding the lower jaw), a less complete juvenile cranium, and some robust cranial fragments from another adult. All display evidence of human modification, such as cut marks, considered to represent mortuary practices rather than cannibalism. Associated layers of sediment produced evidence of the butchery of large mammals such as hippopotamuses and bovines, as well as assemblages of artefacts showing an interesting combination of Middle Stone Age and late Acheulean technology.
Nature http://www.nature.com/nature
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