Evolution of the human hand: approaches to acquiring, analysing and interpreting the anatomical evidence.
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The discovery of fossil hand bones from an early human ancestor at Olduvai Gorge in 1960, at the same level as primitive stone tools, generated a debate about the role of tools in the evolution of the human hand that has raged to the present day. Could the Olduvai hand have made the tools? Did the human hand evolve as an adaptation to tool making and tool use? The debate has been fueled by anatomical studies comparing living and fossil human and nonhuman primate hands, and by experimental observations. These have assessed the relative abilities of apes and humans to manufacture the Oldowan tools, but consensus has been hampered by disagreements about how to translate experimental data from living species into quantitative models for predicting the performance of fossil hands. Such models are now beginning to take shape as new techniques are applied to the capture, management and analysis of data on kinetic and kinematic variables ranging from hand joint structure, muscle mechanics, and the distribution and density of bone to joint movements and muscle recruitment during manipulative behaviour. The systematic comparative studies are highlighting a functional complex of features in the human hand facilitating a distinctive repertoire of grips that are apparently more effective for stone tool making than grips characterising various nonhuman primate species. The new techniques are identifying skeletal variables whose form may provide clues to the potential of fossil hominid hands for one-handed firm precision grips and fine precision manoeuvering movements, both of which are essential for habitual and effective tool making and tool use. (+info)
Isotopes, ice ages, and terminal Proterozoic earth history.
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Detailed correlations of ancient glacial deposits, based on temporal records of carbon and strontium isotopes in seawater, indicate four (and perhaps five) discrete ice ages in the terminal Proterozoic Eon. The close and repeated stratigraphic relationship between C-isotopic excursions and glaciogenic rocks suggests that unusually high rates of organic carbon burial facilitated glaciation by reducing atmospheric greenhouse capacity. The emerging framework of time and environmental change contributes to the improved resolution of stratigraphic and evolutionary pattern in the early fossil record of animals. (+info)
Digital imaging of bone and tooth modification.
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Digital cameras are capable of producing images of cut marks and other three dimensional subjects comparable to those obtained from the scanning electron microscope (SEM). Until now, the SEM has offered unparalleled depth of field and surface rendition. SEM units are, however, expensive to acquire and maintain, and SEM image production is time-intensive. Furthermore, SEM images lack color and are often incapable of imaging bone modifications because of magnification and chamber size limitations. A digital imaging method for producing extremely high depth of field enlargements of three dimensional, sub-millimeter scale objects circumvents these problems. In our presentation we employ four case studies of hard tissue modification related to: (1) the origins of meat-eating in the human lineage; (2) evidence for cannibalistic behavior among Neanderthals; (3) pre-Columbian evidence of North American dentistry; and (4) the earliest evidence of cranial surgery in North America. Procedures for replica production, image-capture, and image enhancement are provided. The digital images produced are compared to those obtained with the SEM. Image processing software, a crucial component of this method, allows complete control of graphic data, making graphic fraud a larger threat than ever before. Issues in ethics stemming from the application of this technology to scientific analysis are considered. (+info)
Genetics and the population history of Europe.
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Analysis of genetic variation among modern individuals is providing insight into prehistoric events. Comparisons of levels and patterns of genetic diversity with the predictions of models based on archeological evidence suggest that the spread of early farmers from the Levant was probably the main episode in the European population history, but that both older and more recent processes have left recognizable traces in the current gene pool. (+info)
Brief review of dinosaur studies and perspectives in Brazil.
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Dinosaur research is developing at very high rates around the world resulting in several new discoveries that are improving our understanding of this terrestrial reptilian clade. Except for the last couple years, the studies of Brazilian dinosaurs have not followed this expansive trend, despite the high potential of several dinosaur localities. So far there are only eight described taxa, four in the last year, representing theropod, sauropod, and one possible prosauropod taxa. Except for footprints, there are no records of ornithischian dinosaurs in the country what is at least partially explainable by the lack of continuous vertebrate fossil collecting program in the country. More funding is necessary to improve the research activities in this field. (+info)
In situ laser-Raman imagery of precambrian microscopic fossils.
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Laser-Raman imagery is a sensitive, noninvasive, and nondestructive technique that can be used to correlate directly chemical composition with optically discernable morphology in ancient carbonaceous fossils. By affording means to investigate the molecular makeup of specimens ranging from megascopic to microscopic, it holds promise for providing insight into aspects of organic metamorphism and biochemical evolution, and for clarifying the nature of ancient minute fossil-like objects of putative but uncertain biogenicity. (+info)
Are plague pits of particular use to palaeoepidemiologists?
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BACKGROUND: The demography and pattern of disease of skeletal assemblages may not accurately reflect those of the living population of which they were once a part. The hypothesis tested here was that skeletons from a mass disaster would more closely approximate to a living population than those from a conventional cemetery. METHOD: Six hundred skeletons recovered from a Black Death plague pit in London were compared with 236 skeletons recovered from an overlying medieval cemetery. Age and sex were determined by standard anthropological means by a single observer and adjustments were made to correct for those skeletons for which either or both could not be established. An estimate of age structure of the living medieval population of London was made, using model life tables. RESULTS: The age and sex distribution and the pattern of disease in the Black Death skeletons did not differ substantially from those in the control group of skeletons. Both assemblages tended to overestimate the numbers in the younger age groups of the model population and underestimate the numbers in the oldest age group. CONCLUSIONS: On the evidence from this single site, a skeletal assemblage from a mass disaster does not provide a better representation of the living population from which it was derived than that from a conventional cemetery. (+info)
Modern human ancestry at the peripheries: a test of the replacement theory.
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The replacement theory of modern human origins stipulates that populations outside of Africa were replaced by a new African species of modern humans. Here we test the replacement theory in two peripheral areas far from Africa by examining the ancestry of early modern Australians and Central Europeans. Analysis of pairwise differences was used to determine if dual ancestry in local archaic populations and earlier modern populations from the Levant and/or Africa could be rejected. The data imply that both have a dual ancestry. The diversity of recent humans cannot result exclusively from a single Late Pleistocene dispersal. (+info)