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83 result(s) for "Ruff, Christopher B."
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Genetic contributions to variation in human stature in prehistoric Europe
The relative contributions of genetics and environment to temporal and geographic variation in human height remain largely unknown. Ancient DNA has identified changes in genetic ancestry over time, but it is not clear whether those changes in ancestry are associated with changes in height. Here, we directly test whether changes over the past 38,000 y in European height predicted using DNA from 1,071 ancient individuals are consistent with changes observed in 1,159 skeletal remains from comparable populations. We show that the observed decrease in height between the Early Upper Paleolithic and the Mesolithic is qualitatively predicted by genetics. Similarly, both skeletal and genetic height remained constant between the Mesolithic and Neolithic and increased between the Neolithic and Bronze Age. Sitting height changes much less than standing height—consistent with genetic predictions—although genetics predicts a small post-Neolithic increase that is not observed in skeletal remains. Geographic variation in stature is also qualitatively consistent with genetic predictions, particularly with respect to latitude. Finally, we hypothesize that an observed decrease in genetic heel bone mineral density in the Neolithic reflects adaptation to the decreased mobility indicated by decreased femoral bending strength. This study provides a model for interpreting phenotypic changes predicted from ancient DNA and demonstrates how they can be combined with phenotypic measurements to understand the relative contribution of genetic and developmentally plastic responses to environmental change.
Limb Bone Structural Proportions and Locomotor Behavior in A.L. 288-1 (\Lucy\)
While there is broad agreement that early hominins practiced some form of terrestrial bipedality, there is also evidence that arboreal behavior remained a part of the locomotor repertoire in some taxa, and that bipedal locomotion may not have been identical to that of modern humans. It has been difficult to evaluate such evidence, however, because of the possibility that early hominins retained primitive traits (such as relatively long upper limbs) of little contemporaneous adaptive significance. Here we examine bone structural properties of the femur and humerus in the Australopithecus afarensis A.L. 288-1 (\"Lucy\", 3.2 Myr) that are known to be developmentally plastic, and compare them with other early hominins, modern humans, and modern chimpanzees. Cross-sectional images were obtained from micro-CT scans of the original specimens and used to derive section properties of the diaphyses, as well as superior and inferior cortical thicknesses of the femoral neck. A.L. 288-1 shows femoral/humeral diaphyseal strength proportions that are intermediate between those of modern humans and chimpanzees, indicating more mechanical loading of the forelimb than in modern humans, and by implication, a significant arboreal locomotor component. Several features of the proximal femur in A.L. 288-1 and other australopiths, including relative femoral head size, distribution of cortical bone in the femoral neck, and cross-sectional shape of the proximal shaft, support the inference of a bipedal gait pattern that differed slightly from that of modern humans, involving more lateral deviation of the body center of mass over the support limb, which would have entailed increased cost of terrestrial locomotion. There is also evidence consistent with increased muscular strength among australopiths in both the forelimb and hind limb, possibly reflecting metabolic trade-offs between muscle and brain development during hominin evolution. Together these findings imply significant differences in both locomotor behavior and ecology between australopiths and later Homo.
Bioarchaeology of Neolithic Çatalhöyük reveals fundamental transitions in health, mobility, and lifestyle in early farmers
The transition from a human diet based exclusively on wild plants and animals to one involving dependence on domesticated plants and animals beginning 10,000 to 11,000 y ago in Southwest Asia set into motion a series of profound health, lifestyle, social, and economic changes affecting human populations throughout most of the world. However, the social, cultural, behavioral, and other factors surrounding health and lifestyle associated with the foraging-to-farming transition are vague, owing to an incomplete or poorly understood contextual archaeological record of living conditions. Bioarchaeological investigation of the extraordinary record of human remains and their context from Neolithic Çatalhöyük (7100–5950 cal BCE), a massive archaeological site in south-central Anatolia (Turkey), provides important perspectives on population dynamics, health outcomes, behavioral adaptations, interpersonal conflict, and a record of community resilience over the life of this single early farming settlement having the attributes of a protocity. Study of Çatalhöyük human biology reveals increasing costs to members of the settlement, including elevated exposure to disease and labor demands in response to community dependence on and production of domesticated plant carbohydrates, growing population size and density fueled by elevated fertility, and increasing stresses due to heightened workload and greater mobility required for caprine herding and other resource acquisition activities over the nearly 12 centuries of settlement occupation. These changes in life conditions foreshadow developments that would take place worldwide over the millennia following the abandonment of Neolithic Çatalhöyük, including health challenges, adaptive patterns, physical activity, and emerging social behaviors involving interpersonal violence.
Gradual decline in mobility with the adoption of food production in Europe
Significance Declining mobility levels following the Pleistocene had profound effects on human demography, social organization, and health, but the exact timing and pace of this critical change are unknown. Here we examine direct evidence for changing mobility levels from limb bone structural characteristics in a large sample of European skeletons spanning the past 30,000 y. Our results show that mobility first declined during the Neolithic, at the onset of food production, but that the decline was gradual, continuing for several thousand years as agriculture intensified. No change in relative limb strength occurred during the past 2,000 y. Thus, the more gracile modern human skeleton is a result of increased sedentism tied to food production, not subsequent mechanization and industrialization. Increased sedentism during the Holocene has been proposed as a major cause of decreased skeletal robusticity (bone strength relative to body size) in modern humans. When and why declining mobility occurred has profound implications for reconstructing past population history and health, but it has proven difficult to characterize archaeologically. In this study we evaluate temporal trends in relative strength of the upper and lower limb bones in a sample of 1,842 individuals from across Europe extending from the Upper Paleolithic [11,000–33,000 calibrated years (Cal y) B.P.] through the 20th century. A large decline in anteroposterior bending strength of the femur and tibia occurs beginning in the Neolithic (∼4,000–7,000 Cal y B.P.) and continues through the Iron/Roman period (∼2,000 Cal y B.P.), with no subsequent directional change. Declines in mediolateral bending strength of the lower limb bones and strength of the humerus are much smaller and less consistent. Together these results strongly implicate declining mobility as the specific behavioral factor underlying these changes. Mobility levels first declined at the onset of food production, but the transition to a more sedentary lifestyle was gradual, extending through later agricultural intensification. This finding only partially supports models that tie increased sedentism to a relatively abrupt Neolithic Demographic Transition in Europe. The lack of subsequent change in relative bone strength indicates that increasing mechanization and urbanization had only relatively small effects on skeletal robusticity, suggesting that moderate changes in activity level are not sufficient stimuli for bone deposition or resorption.
Recent origin of low trabecular bone density in modern humans
Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.
Effects of the energy balance transition on bone mass and strength
Chronic positive energy balance has surged among societies worldwide due to increasing dietary energy intake and decreasing physical activity, a phenomenon called the energy balance transition. Here, we investigate the effects of this transition on bone mass and strength. We focus on the Indigenous peoples of New Mexico in the United States, a rare case of a group for which data can be compared between individuals living before and after the start of the transition. We show that since the transition began, bone strength in the leg has markedly decreased, even though bone mass has apparently increased. Decreased bone strength, coupled with a high prevalence of obesity, has resulted in many people today having weaker bones that must sustain excessively heavy loads, potentially heightening their risk of a bone fracture. These findings may provide insight into more widespread upward trends in bone fragility and fracture risk among societies undergoing the energy balance transition.
Body Size, Body Proportions, and Encephalization in a Middle Pleistocene Archaic Human from Northern China
The unusual discovery of associated cranial and postcranial elements from a single Middle Pleistocene fossil human allows us to calculate body proportions and relative cranial capacity (encephalization quotient) for that individual rather than rely on estimates based on sample means from unassociated specimens. The individual analyzed here (Jinniushan) from northeastern China at 260,000 years ago is the largest female specimen yet known in the human fossil record and has body proportions (body height relative to body breadth and relative limb length) typical of coldadapted populations elsewhere in the world. Her encephalization quotient of 4.15 is similar to estimates for late Middle Pleistocene humans that are based on mean body size and mean brain size from unassociated specimens.
Skeletal variation and adaptation in Europeans : upper Paleolithic to the twentieth century
A comprehensive analysis of changes in body form and skeletal robusticity from the Terminal Pleistocene through the Holocene, leading to the modern European human phenotype. Skeletal Variation and Adaptation in Europeans: Upper Paleolithic to the Twentieth Century brings together for the first time the results of an unprecedented large-scale investigation of European skeletal remains. The study was conducted over ten years by an international research team, and includes more than 2, 000 skeletons spanning most of the European continent over the past 30, 000 years, from the Early Upper Paleolithic to the 20th century. This time span includes environmental transitions from foraging to food production, small-scale to large-scale urban settlements, increasing social stratification and mechanization of labor, and climatic changes. Alterations in body form and behavior in response to these transitions are reconstructed through osteometric and biomechanical analyses. Divided into four sections, the book includes an introduction to the project and comprehensive descriptions of the methods used; general continent-wide syntheses of major trends in body size, shape, and skeletal robusticity; detailed regional analyses; and a summary of results. It also offers a full data set on an external website. * Brings together data from an unprecedented large-scale study of human skeletal and anatomical variations * Includes appendix of specific information from each research site * Synthesizes data from spatial, temporal, regional, and geographical perspectives Skeletal Variation and Adaptation in Europeans will be a valuable resource for bioarchaeologists, palaeoanthropologists, forensic anthropologists, medical historians, and archaeologists at both the graduate and post-graduate level.
Bioarchaeology of Neolithic Çatalhöyük: Lives and Lifestyles of an Early Farming Society in Transition
The bioarchaeological record of human remains viewed in the context of ecology, subsistence, and living circumstances provides a fundamental source for documenting and interpreting the impact of plant and animal domestication in the late Pleistocene and early to middle Holocene. For Western Asia, Çatalhöyük (7100-5950 cal BC) in central Anatolia, presents a comprehensive and contextualized setting for interpreting living circumstances in this highly dynamic period of human history. This article provides an overview of the bioarchaeology of Çatalhöyük in order to characterize patterns of life conditions at the community level, addressing the question, What were the implications of domestication and agricultural intensification, increasing sedentism, and population growth for health and lifestyle in this early farming community? This study employs demography, biogeochemistry, biodistance analysis, biomechanics, growth and development, and paleopathology in order to identify and interpret spatial and temporal patterns of health and lifestyle under circumstances of rapid population growth and aggregation and changing patterns of acquiring food and other resources. The record suggests that the rapid growth in population size was fueled by increased fertility and birthrate. Although the household was likely the focus of economic activity, our analysis suggests that individuals interred in houses were not necessarily biologically related. Predictably, the community employed resource extraction practices involving increased mobility. Although oral and skeletal indicators suggest some evidence of compromised health (e.g. elevated subadult infection, dental caries), growth and development of juveniles and adult body size and stature indicate adjustments to local circumstances.
Body mass and encephalization in Pleistocene Homo
Many dramatic changes in morphology within the genus Homo have occurred over the past 2 million years or more, including large increases in absolute brain size and decreases in postcanine dental size and skeletal robusticity. Body mass, as the 'size' variable against which other morphological features are usually judged, has been important for assessing these changes 1–5 . Yet past body mass estimates for Pleistocene Homo have varied greatly, sometimes by as much as 50% for the same individuals 2,3,6–12 . Here we show that two independent methods of body-mass estimation yield concordant results when applied to Pleistocene Homo specimens. On the basis of an analysis of 163 individuals, body mass in Pleistocene Homo averaged significantly (about 10%) larger than a representative sample of living humans. Relative to body mass, brain mass in late archaic H. sapiens (Neanderthals) was slightly smaller than in early 'anatomically modern' humans, but the major increase in encephalization within Homo occurred earlier during the Middle Pleistocene (600–150 thousand years before present (kyr BP)), preceded by a long period of stasis extending through the Early Pleistocene (1,800 kyr BP).