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The principles and practice of human evolution research: Are we asking questions that can be answered?

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Abstract

The research agenda of paleoanthropology involves many topics and methodologies. Fossil specimens are allocated to species, and those species are assigned to the hominin clade. After that we want to know how they are related to each other, what they ate, how much they weighed, how smart they were, etc. We also want to know about the origin of particular attributes of hominins, such as our delayed growth and development, bipedalism, and language. The data available to answer these complex questions are confounded by fragmentary fossil specimens, small sample sizes, limited opportunities for controlled experimentation, and the inherent limitations of historical data. Also, because many traits are effectively unique to hominins, even observational comparative studies are inevitably limited in what they can tell us, if not impossible to conduct. We explore how these limitations should, but often do not, constrain the questions that paleoanthropologists should attempt to answer.

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... It is like saying, for example, that just because a cure/solution has been found in the course of biology history for cleft lips, cleft palates, epilepsy, tuberculosis, etc. any review/research of those and many similar topics of human life has been already closed and removed from scholarly work. As paleoanthropologists Smith and Wood (2017) reminded all researchers (of biology and skin color, including), "the overall [emphasis in original] research agenda of a discipline… must conform to science norms. This means, among other things, that… its knowledge is cumulative and progressive" (p. ...
... To elaborate, there are broadly speaking four disciplines involved in the comparison suggested supra, namely: (1) anatomy; a sample of bones/skull taken from individual A, (2) physiology; a sample of a black skin cut taken from individual B, (3) paleoecology; a sample of a leaf taken from plant A, and (4) climatology; a sample of a temperature taken from spot A. As can be anticipated, the listed samples are units of analysis/research and worlds completely separate and different from one another. The issue was well raised by Smith (2016) and Smith and Wood (2017), namely, how counterproductive and almost impossible is the endeavor to consider a unity of study as representative of the concerned group and of variation (regarding the group and its individuals), not to mention surrounding mechanisms. The idea here refers to Gloger key argument about the complexity of variability mentioned earlier (Gloger, 1833). ...
... Such practices tend to poison the working atmosphere of black skin research. As paleoanthropologists Smith and Wood (2017) warned, "we generate comprehensive narratives knowing that we do not have all of the relevant data… There is much we would like to know about human evolutionary history, but wanting to know something does not make it knowable" (p. 677). ...
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Unlike various topics of human life that recurringly naggingly preoccupy scholars, black skin tends to be considered by prestigious biology and science publication outlets as a closed and disposed-of topic. The present paper is not one of experiment, but rather the paper is a long-due comprehensive review of black skin scholarship, using a dominant theory of this scholarship, and suggesting newer insights for future research. Known since Antiquity, black skin -- euphemistically called dark sin -- has become the topic of repeated public debate in recent decades. Part of the reason is that although race is believed to be scientifically nonexistent skin color is not. Meanwhile, among the theories explaining black skin, Gloger rule/theory stands out to be the most popular. While multitudes of reviews have examined Gloger theory, few have confronted the theory with the arguments of Gloger himself. This might be because Gloger writings remain untranslated and unknown to English readership. Although Gloger was an ornithologist by profession, his arguments had immense ramifications far beyond the study of birds. The present paper focused on the key arguments of Gloger to present a critical assessment of black skin materials. To this effect, a comprehensive, historical background of Gloger theory was used along with recent research to bring in sharper relief Gloger teachings about skin color. In light of Gloger critiques, it was determined that Gloger theory is no less than inadequate and so is the description of black skin as a product of natural selection. Taken-for-granted theories and resultant arguments of black skin were reversed and paths for future skin color work were proposed. Gloger arguments highlight variability among species and across latitudes.
... Terrestrial bipedalism is widely regarded as a shared-derived characteristic of the hominin clade and understanding its evolution is one of the central foci of biological anthropology (Darwin, 1871;Wasburn, 1967;Fleagle et al., 1981;Richmond et al., 2001;Gebo, 1996;Begun, 2004;Lovejoy et al., 2009a;White et al., 2015). There are numerous adaptive explanations for the origin of bipedalism (Darwin, 1871;Hewes, 1961;Lovejoy, 1981;Rose, 1991;Washburn, 1960;Hunt, 1996) that are inherently difficult to test directly (Smith and Wood, 2017), but each of them depends on alternative hypothetical models for the morphology and locomotor behavior of the human-chimpanzee last common ancestor (LCA; Richmond et al., 2001). Hypotheses for the locomotor behavior of the LCA include vertical climbing (Stern, 1975;Prost, 1980;Fleagle et al., 1981), terrestrial knuckle-walking (Wasburn, 1967;Gebo, 1992;Gebo, 1996;Pilbeam, 1996;Richmond and Strait, 2000;Richmond et al., 2001;Begun, 2004;Inouye and Shea, 2004), belowbranch suspension (Keith, 1923;Tuttle, 1969;Young et al., 2015), arboreal bipedality (Thorpe et al., 2007), and more generalized quadrupedalism with slow, deliberate climbing (Lovejoy et al., 2009a;White et al., 2009;White et al., 2015). ...
... Hominin upright walking therefore likely emerged in the context of semi-terrestrial quadrupedalism. Explaining the adaptive origin of hominin bipedalism (i.e., 'why' bipedalism evolved) will continue to be a challenging endeavor (Smith and Wood, 2017). However, the comparative and fossil material provides evidence for patterns of evolution (i.e., 'how' bipedalism evolved) and strongly suggests that hypotheses of a non-African ape-like morphology for the foot of the Homo-Pan LCA (Lovejoy et al., 2009a;White et al., 2015;Lovejoy et al., 2009b) are inconsistent with the results from this study. ...
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The ancestral condition from which humans evolved is critical for understanding the adaptive origin of bipedal locomotion. The 4.4 million-year-old hominin partial skeleton attributed to Ardipithecus ramidus preserves a foot that purportedly shares morphometric affinities with monkeys, but this interpretation remains controversial. Here I show that the foot of Ar. ramidus is most similar to living chimpanzee and gorilla species among a large sample of anthropoid primates. The foot morphology of Ar. ramidus suggests that the evolutionary precursor of hominin bipedalism was African ape-like terrestrial quadrupedalism and climbing. The elongation of the midfoot and phalangeal reduction in Ar. ramidus relative to the African apes is consistent with hypotheses of increased propulsive capabilities associated with an early form of bipedalism. This study provides evidence that the modern human foot was derived from an ancestral form adapted to terrestrial plantigrade quadrupedalism.
... Based on the distribution of most first appearance datums in the Plio-Pleistocene palaeoanthropological record, the Eastern African tropical zone likely represents the centre of endemism of Oldowan and Acheulean toolmakers (Foley, 2018). However, the palaeoanthropological record is incomplete, palimpsestic, spatially biased, and imprecisely dated, which warrants caution as to the accuracy of the foregoing, and any other, evolutionary model (Bailey, 2007;Smith and Wood, 2017). From an archaeological perspective, these limitations necessitate the thorough examination of stone tools, which outnumber any other artefact type due to their durability, using different theoretical and methodological approaches to maximize their interpretive remit. ...
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Eastern Africa's Plio-Pleistocene palaeoanthropological record has shaped our understanding of human biological and cultural evolution. Over the years, raw material sourcing has emerged as an important research topic in lithic analysis as it can allow for the identification of resource extraction points and transport distances as a means to infer other aspects of hominin behaviour that are of high evolutionary significance. The goal of this article is to review and synthesise the aims, methods, challenges, and knowledge on raw material sourcing from Plio-Pleistocene contexts in Eastern Africa. Beginning with a review of the Oldowan and Acheulean records, four over-arching patterns are identified based on evidence from 130 localities. First, hominin toolmakers regularly exerted selective criteria when choosing raw materials by way of opportunistic and more specialised procurement strategies. Second, the fragmentation of technological activities across the palaeolandscape emerged as a behavioural characteristic among Oldowan toolmakers before the first appearance datum of the Acheulean. Third, hominins across Eastern Africa preferentially utilised igneous rock types followed by metamorphic and sedimentary lithologies mirroring the regional lithostratigraphy. Finally, Acheulean toolmakers largely mimicked their Oldowan counterparts in terms of raw material provisioning until the late Early Pleistocene, when they began to engage in qualitatively different behaviour best evidenced by stone transport over longer distances. This state of archaeological knowledge serves as the basis to then review the theoretical and methodological underpinnings of raw material sourcing followed by interpretive challenges. On a fundamental level, the identification of raw material sources is contingent on the implementation of a systematic sequence of analysis in which the resulting data abide to the provenance postulate. This serves to preface a devoted section on the array of analytical methods that can be successfully employed by archaeologists to source raw materials. Proven and innovative methods are identified by bringing into dialogue key factors such as accuracy, precision, reproducibility, discriminatory power, sensitivity, destructiveness, throughput, cost, ease, and the question of spatial scale. According to cost-benefit considerations, analytical methods that fall under the umbrella of geochemical fingerprinting are found to generally outperform macroscopic and petrographic techniques. It is also argued that characterising non-obsidian lithologies is best accomplished using more than one analytical method, with the understanding that once positive baseline results are obtained subsequent testing can be narrowed down from a methodological standpoint. Regardless of the characterisation method, it is imperative to implement effective means to analyse the resulting data, which constitutes this article's penultimate section. Ranging from traditional graphical data representations to multivariate statistics and emerging branches of artificial intelligence, there are countless means through which characteristic source signals can be identified regardless of rock type. The final section reviews common interpretive challenges when studying raw material provisioning in deep time. While the concepts of mobility, time-averaging, recycling, source differentiation, and selection criteria each present unique challenges, it is argued that they can be reasonably overcome by way of multidisciplinary evidence. Ultimately, it is found that the future of raw material sourcing from Plio-Pleistocene contexts in Eastern Africa is promising given what is currently known along with the subfield's robust foundations.
... Consider an illustrative example. Smith and Wood, (2017) argue that unique hominin traits block epistemic access to the evolutionary past. They begin by defining uniqueness: ...
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Researchers in the life sciences often make uniqueness attributions; about branching events generating new species, the developmental processes generating novel traits, and the distinctive cultural selection pressures faced by hominins. Yet since uniqueness implies non-recurrence, such attributions come freighted with epistemic consequences. Drawing on the work of Aviezer Tucker, we show that a common reaction to uniqueness attributions is pessimism: both about the strength of candidate explanations as well as the ability to even generate such explanations. Looking at two case studies—elephant trunks and human teaching—we develop a more optimistic account. As we argue, uniqueness attributions are revisable claims about the availability of several different kinds of comparators. Yet even as researchers investigate the availability of such comparators, they are able to mobilize complex sets of empirical and theoretical tools. Rather than hindering scientific investigation, then, we argue that uniqueness attributions often spur the generation of a range of epistemic goods.
... Comment démêler cet écheveau? -Dans un futur proche, pour être sûr de développer au mieux des programmes de recherche fondés sur des questions auxquelles il est effectivement possible de fournir des réponses [ 44 ], il deviendra nécessaire, pour la Paléoanthropologie en tant que discipline scientifique, de dépasser l'ambiguïté de son positionnement entre approche 'idiographique' (éminemment narrative, historique, typique des sciences humaines) et approche 'nomothétique' (basée sur l'application de la méthode hypothético-déductive pour générer de modèles et la formulation systématique d'hypothèses testables). ...
... So it is understandable that researchers have sought, and continue to seek, to explain why modern humans have the wherewithal to contribute to and publish volumes about distinguished archeologists, whereas our closest living relatives do not. But 'why' questions are rarely, if ever, scientifically tractable (Smith and Wood, 2017), and it is to John Gowlett's credit that his career has sensibly focused on 'what' and 'how' questions. Gowlett has shown time and time again that he makes wise choices about his research agenda. ...
... The starting point for macroevolutionary analyses in paleoanthropology ought to be that, before any pattern in the fossil record is causally linked to climate, it is demonstrably shown that that pattern is not an artifact of sampling or poor fossil record quality. This requirement has been overlooked by paleoanthropologists, archaeologists, and climatologists alike, and has severely impacted the interpretation of macroevolutionary pattern and process in the early hominin fossil record (51). Becoming cognizant of the rapidly advancing study of fossil record quality in paleobiology, particularly since the pioneering work of Raup (13,23), should be at the center of 21st century paleoanthropology. ...
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Significance Paleoanthropologists have long been intrigued by the observed patterns of human evolution, including species diversity, and often invoked climatic change as the principal driver of evolutionary change. Here, we investigate whether the early hominin fossil record is of suitable quality to test these climate-forcing hypotheses. Specifically, we compare early hominin diversity to sampling metrics that quantify changes in fossil preservation and sampling intensity between 7 and 1 million years ago. We find that observed diversity patterns are governed by sporadic sampling and do not yield a genuine evolutionary signal. Many more fossil discoveries are required before existing hypotheses linking climate and evolution can be meaningfully tested.
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Accurate sequence and assembly of genomes is a critical first step for studies of genetic variation. We generated a high-quality assembly of the gorilla genome using single-molecule, real-time sequence technology and a string graph de novo assembly algorithm. The new assembly improves contiguity by two to three orders of magnitude with respect to previously released assemblies, recovering 87% of missing reference exons and incomplete gene models. Although regions of large, high-identity segmental duplications remain largely unresolved, this comprehensive assembly provides new biological insight into genetic diversity, structural variation, gene loss, and representation of repeat structures within the gorilla genome. The approach provides a path forward for the routine assembly of mammalian genomes at a level approaching that of the current quality of the human genome.
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Causal explanations involve both narrative and laws. To explain some event as the effect of other events, we must at least demonstrate (1) that the cause and effect both took place, with the cause preceding the effect, and (2) that the effect belongs to a class of events that can be reliably expected to follow from a class of events to which the cause belongs. Demonstration (1) is a narrative; demonstration (2) is a law. Narrative and "contingency" are not satisfactory substitutes for laws in explaining evolutionary events. If any evolutionary events are explicable, there must be evolutionary laws, and the course of evolution must therefore be to some extent predictable. However, many evolutionary events will probably always elude causal explanation. In particular, as Hume pointed out, qualitatively unique events cannot be explained causally. If human beings possess qualitatively unique traits, their causes must remain a subject for speculation. The only evolutionary events we can explain, in our own lineage or any other, are those that conform to recurring regularities.
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Taphonomy established tiself in paleontology primarily as a subdiscipline of paleoecology, but it has evolved into a much broader study of the ways in which preservation affects the fossil record. The past decade has seen a change in emphasis from descriptive taphonomic studies of fossil assemblages to more experimental, process-oriented investigations of necrolysis, stratification, and diagenesis of organic remains in modern environments. These actualistic studies are increasing the sophistication of taphonomic analysis in the fossil record by sharpening the diagnosis of bias in paleontological data and by providing a base line for quantitative modelling of preservational patterns. The analysis of bias is also expanding into the evaluation of temporal resolution in the fossil record (sample acuity, stratigraphic completeness), and taphonomic research is thus contributing to broad-scale problems in evolution, biogeography, and biostratigraphy. In addition, taphonomic studies are providing new insights into paleoenvironmental reconstruction and into the direct paleobiological significance of post mortem processes such as the behavior of scavengers and the role of dead hardparts in structuring benthic communities. One of taphonomy's most promising new frontiers is comparative analysis applied to different taxonomic groups within assemblages and across environments, tectonic settings, and climatic regimes. All of this currently active research is contributing to a better understanding of the fossil record as the result of a dynamic, evolving, integrated system of biological and sedimentological processes that have both limited and enhanced knowledge of Earth history.-Authors
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Homoplasy has been a prominent issue in primate systematics and phylogeny for as long as people have been studying human evolution. In the past, homoplasy, in the form of parallel evolution, was often considered the dominant theme in primate evolution. Today, it receives blame for difficulties in phylogenetic analysis, but is essential in the study of adaptation. This paper reviews the history of study of homoplasy, methods of defining homoplasy, and methodological and biological factors that generate homoplasy. A post hoc definition of homology and homoplasy, based on patterns of character distributions and their congruence or incongruence on a cladogram, is the most consistent method of recognizing these phenomena. Defined this way, homology and homoplasy are mutually exclusive. However, when different levels of analysis are examined, it is seen that homoplasy at one level, such as adult phenotype, often exists simultaneously with homology at a different level, such as developmental process. Thus, in some cases, patterns of homoplasy may point to underlying similarities that reflect the shared heritage of a particular clade. This is an old concept that is being renewed on the strength of recent trends in developmental biology. Factors that influence homoplasy include character definition and a host of biological factors, such as developmental constraints, allometry, and adaptation. These interact with one another to provide explanations of homoplastic patterns. Because of the repetition of events, explanations of homoplastic features are often more reliable than those for homologous features, and serve as effective tests for hypotheses of evolutionary process. In some cases, particular explanations of homoplasy lead to generalizations about the likelihood of homoplasy in a type of structure. The structure may be adaptive or highly epigenetic, or it may belong to an anatomical system considered to be more prone to homoplasy than others. However, our review shows that these generalizations are usually based on theory, and contradictory expectations can be developed under different theoretical models. More rigorous empirical studies are necessary to discover what, if any, generalizations can be made about the likelihood of homoplasy in different types of characters. Yrbk Phys Anthropol 42:189-232, 1999.
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The point of this article is indicated by the title: Explanation and description are different activities. For example, although both are essential features of natural science, their roles are different, they have different purposes, and they are evaluated on different grounds. Consequently the ways in which they can be problematic are different. The arguments leading to these conclusions and examples of problematic explanations are given in this article.
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Selon la these de sous-determination (W.V.Quine), des theories scientifiques radicalement opposees peuvent se fonder sur des preuves similaires. En precisant cette these, l'A. cherche a en evaluer sa validite.
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Covers: the Darwinian background; early consensus on human ancestry; the rise and fall of Ramapithecus; Dart's ape (Australopithecus africanus); the australopithecines become human; the human genus; retrospect and prospect.-from Authors
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Among the intriguing issues over which philosophers and historians tend to disagree is the general character of historical explanations of events that are unique. Philosophers argue that every event is actually unique, but that any event may be explained, nevertheless, insofar as it happens to be one of a certain kind. Historians protest that this conception ignores the particularity of individual events and especially the fact that such an event may very well be the only one of its kind. As a result, historians tend to dismiss the philosopher's arguments as ‘purely theoretical’, while philosophers tend to dismiss the historian's retort as ‘merely methodological’, phrases that, within this context, at least, are clearly intended to have pejorative connotations. The purpose of this paper is to undertake an arbitration of this dispute by indicating what appear to be the strengths and weaknesses of both positions, while suggesting the view that more is involved here than either side at various times has been prepared to admit.
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The extensive, persistent ecological dominance of humans is unprecedented. We display a highly derived social adaptation involving uniquely extensive cooperation among nonclose Kin. Further, humans possess adaptive capabilities, including language, high cognitive function, and technological virtuosity not previously seen on this planet. Moreover, this suite of properties emerged and was refined very rapidly on a geological time scale. These diverse features of humans present what is referred to as the "human uniqueness problem. "A theoretical interpretation of these phenomena is one of the largest remaining challenges to the scientific enterprise. While many interpretations have been proposed-several containing important individual insights-none has yet proven robust or complete. A straightforward resolution of the human uniqueness problem is proposed. It is argued that coalitional enforcement is necessary and sufficient to allow extensive nonkin cooperation, leading to all major elements of human uniqueness. Coalitional enforcement arose uniquely in humans when the animals that founded the Home clade acquired the ability to kill or injure conspecifics from a substantial distance. This resulted from the evolution of hominid virtuosity at accurate, high-momentum throwing and clubbing; previously supposed to be adaptations for hunting, predator defense or individual aggression. No previous animal could reliably kill or injure conspecifics remotely. This ability dramatically reduced the individual cost of punishing noncooperative behavior by allowing these costs to be distributed among multiple cooperators. The capacity for coalitional enforcement drove the evolution of a cooperative social adaptation stably and autocatalytically from the origin of incipient Home about 2 million years ago through to the present moment-including socially supported, ultimately spectacular refinements in weaponry and social monitoring with attendant increases in efficiency of coalitional enforcement and thus in the extent of human cooperation. Its details rendered this evolutionary process very rapid. This theory is believed to be robust and relatively complete. For example, coalitional enforcement is necessary and sufficient to allow for the evolution of language in an ape. Further, given the likely functional organization of the ancestral vertebrate mind, the coalitional enforcement hypothesis predicts, in addition to genetic information the emergence of a second stream of design information in Home, susceptible to Darwinian selection. A novel source of design information has long been suspected on empirical and intuitive grounds to be responsible for the uniquely high level of human adaptive sophistication. The unprecedented cognitive power of human minds is also predicted by these implications of the theory. Lastly, the "cognitive explosion" associated with the relatively recent appearance of Behaviorally modern humans is predicted by the theory, as is the increasing size of human political units. The coalitional enforcement hypothesis and its immediate implications now enable the formerly elusive unification of diverse fields of study, including human biology, psychology, linguistics, paleontology, archaeology, anthropology, history, and economics. Copyright
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Taphonomy plays diverse roles in paleobiology. These include assessing sample quality relevant to ecologic, biogeographic, and evolutionary questions, diagnosing the roles of various taphonomic agents, processes and circumstances in generating the sedimentary and fossil records, and reconstructing the dynamics of organic recycling over time as a part of Earth history. Major advances over the past 15 years have occurred in understanding (1) the controls on preservation, especially the ecology and biogeochemistry of soft-tissue preservation, and the dominance of biological versus physical agents in the destruction of remains from all major taxonomic groups (plants, invertebrates, vertebrates); (2) scales of spatial and temporal resolution, particularly the relatively minor role of out-of-habitat transport contrasted with the major effects of time-averaging; (3) quantitative compositional fidelity; that is, the degree to which different types of assemblages reflect the species composition and abundance of source faunas and floras; and (4) large-scale variations through time in preservational regimes (megabiases), caused by the evolution of new bodyplans and behavioral capabilities, and by broad-scale changes in climate, tectonics, and geochemistry of Earth surface systems. Paleobiological questions regarding major trends in biodiversity, major extinctions and recoveries, timing of cladogenesis and rates of evolution, and the role of environmental forcing in evolution all entail issues appropriate for taphonomic analysis, and a wide range of strategies are being developed to minimize the impact of sample incompleteness and bias. These include taphonomically robust metrics of paleontologic patterns, gap analysis, equalizing samples via rarefaction, inferences about preservation probability, isotaphonomic comparisons, taphonomic control taxa, and modeling of artificial fossil assemblages based on modern analogues. All of this work is yielding a more quantitative assessment of both the positive and negative aspects of paleobiological samples. Comparisons and syntheses of patterns across major groups and over a wider range of temporal and spatial scales present a challenging and exciting agenda for taphonomy in the coming decades.
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This paper's theme is that analogies drawn from the cercopithecine tribe Papionini, especially the African subtribe Papionina (baboons, mangabeys, and mandrills), can be a valuable source of insights about the evolution of the human tribe, Hominini, to complement homologies found in extant humans and/or African apes. Analogies, involving a “likeness of relations” of the form “A is to B, as X is to Y,” can be usefully derived from nonhomologous (homoplastic) resemblances in morphology, behavior, ecology, or population structure. Pragmatically, the papionins are a fruitful source of analogies for hominins because they are phylogenetically close enough to share many basic attributes by homology, yet far enough that homoplastic modifications of these features are easily recognized as such. In “The Seedeaters,” an analogy between Theropithecus among baboons and Australopithecus africanus among hominines was the source of a widely discussed (and often misrepresented) diet-based scenario of hominin origins that explained previously unassociated hominin apomorphies, interpreted basal hominins as nonhuman rather than prehuman primates, and accommodated a basal hominin adaptive radiation of at least two lines.
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Although scientists are aware that humans share the same biological heritage as do all other organisms on the planet, the reliance of Homo sapiens on culture and cooperation has resulted in what can best be described as “a spectacular evolutionary anomaly.”1:11 The extra-somatic adaptations, technological dominance, and success of our species in colonizing every terrestrial habitat have no parallel.2 Moreover, Homo sapiens accounts for about eight times as much biomass as do all other terrestrial wild vertebrates combined,3 an amount equivalent to the biomass of all 14,000+ species of ants,4 the most successful terrestrial invertebrates. Human societies are complex, with more specialized economic niches in the United States than the total number of mammalian species on the planet.5 While some might suggest that only post-industrial humans achieved stunning biological success, data suggest that humans living as hunter-gatherers would have attained a world population of more than 70 million individuals6 and a total biomass greater than that of any other large vertebrate on the planet if agriculture had not been repeatedly invented as they spread.
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One of the things that distinguishes science from nonscientific discourse is the incorporation of its hypotheses into theoretical structures. Like parapsychology, the study of human evolution lacks theoretical content and connections. This lack is due, in part, to the collapse of the classical primatological synthesis in the 1970s. It is due in larger measure to a persistent anthropological focus on human uniqueness as the phenomenon to be explained. Such supposedly unique human features as large brains, language, conceptual thinking, and upright bipedalism are uniquely human by definition rather than as a matter of empirical fact. Much scientific effort and ingenuity has gone into redefining such characteristics whenever discoveries about other animals have posed a threat to human uniqueness. But since by definition qualitatively unique phenomena do not conform to overarching laws that apply to similar cases, they must remain theoretically inexplicable. Paleoanthropology should aim at increasing its theoretical content by reducing the list of qualitative human uniquenesses-and eliminating it altogether if possible.
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The paper explicates unique events and investigates their epistemology. Explications of unique events as individuated, different, and emergent are philosophically uninteresting. Unique events are topics of why-questions that radically underdetermine all their potential explanations. Uniqueness that is relative to a level of scientific development is differentiated from absolute uniqueness. Science eliminates relative uniqueness by discovery of recurrence of events and properties, falsification of assumptions of why-questions, and methodological simplification e.g. by explanatory methodological reduction. Finally, an overview of contemporary philosophical disputes that hinge on issues of uniqueness emphasizes its philosophical significance.
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This paper aims to clarify the meaning, and explain the utility, of the case study method, a method j often practiced but little understood. A "case study," I argue, is best defined as an intensive study of a single unit with an aim to generalize across a larger set of units. Case studies rely on the same sort of covariational evidence utilized in non-case study research. Thus, the case study method is correctly understood as a particular way of defining cases, not a way of analyzing cases or a way of modeling causal relations. I show that this understanding of the subject illuminates some of the persistent ambiguities of case study work, ambiguities that are, to some extent, intrinsic to the enterprise. The travails of the case study within the discipline of political science are also rooted in an insufficient appreciation of the methodological tradeoffs that this method calls forth. This paper presents the familiar contrast between case study and non-case study work as a series of characteristic strengths and weaknesses - affinities -rather than as antagonistic approaches to the empirical world. In the end, the perceived hostility between case study and non-case study research is largely unjustified and, perhaps, deserves to be regarded as a misconception. Indeed, the strongest conclusion to arise from this methodological examination concerns the complementarity of single-unit and cross-unit research designs.
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What makes us human? Specialists in each discipline respond through the lens of their own expertise. In fact, 'anthropogeny' (explaining the origin of humans) requires a transdisciplinary approach that eschews such barriers. Here we take a genomic and genetic perspective towards molecular variation, explore systems analysis of gene expression and discuss an organ-systems approach. Rejecting any 'genes versus environment' dichotomy, we then consider genome interactions with environment, behaviour and culture, finally speculating that aspects of human uniqueness arose because of a primate evolutionary trend towards increasing and irreversible dependence on learned behaviours and culture - perhaps relaxing allowable thresholds for large-scale genomic diversity.
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The comparison of human and chimpanzee macromolecules leads to several inferences: 1) Amino acid sequencing, immunological, and electrophoretic methods of protein comparison yield concordant estimates of genetic resemblance. These approaches all indicate that the average human polypeptide is more than 99 percent identical to its chimpanzee counterpart. 2) Nonrepeated DNA sequences differ more than amino acid sequences. A large proportion of the nucleotide differences between the two species may be ascribed to redundancies in the genetic code or to differences in non-transcribed regions. 3) The genetic distance between humans and chimpanzees, based on electrophoretic comparison of proteins encoded by 44 loci is very small, corresponding to the genetic distance between sibling species of fruit flies or mammals. Results obtained with other biochemical methods are consistent with this conclusion. However, the substantial anatomical and behavioral differences between humans and chimpanzees have led to their classification in separate families. This indicates that macromolecules and anatomical or behavioral features of organisms can evolve at independent rates. 4) A relatively small number of genetic changes in systems controlling the expression of genes may account for the major organismal differences between humans and chimpanzees. Some of these changes may result from the rearrangement of genes on chromosomes rather than from point mutations (53).
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Several workers have observed that there is an extremely close immunological resemblance between the serum albumins of apes and man. Our studies with the quantitative micro-complement fixation method confirm this observation. To explain the closeness of the resemblance, previous workers suggested that there has been a slowing down of albumin evolution since the time of divergence of apes and man. Recent evidence, however, indicates that the albumin molecule has evolved at a steady rate. Hence, we suggest that apes and man have a more recent common ancestry than is usually supposed. Our calculations lead to the suggestion that, if man and Old World monkeys last shared a common ancestor 30 million years ago, then man and African apes shared a common ancestor 5 million years ago, that is, in the Pliocene era.
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When trying to assess the implications of recent deep shifts in the philosophy of science for the broader arena of medicine, the theme that most readily comes to mind is underdetermination. In scientific research one always hopes for determination: that the world should determine the observations we make of it; that evidence should determine the theories we adopt; that the practice of science should determine results independent of the sort of society in which that practice takes place. In this essay, doubts cast on each of these ideas by recent work in philosophy of science will be discussed and the consequences for philosophy of medicine will be indicated.
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Excerpt There are three reasons why this is an appropriate time to discuss the origin of man. The first is the finding of abundant fossils of a new kind of missing link in South Africa. The man-like apes indicate an unanticipated stage in human evolution which radically alters all current theories of human origins. The second reason is that, through the work of numerous geneticists, zoologists, and paleontologists, a theoretical framework is now available which is far superior to any previous evolutionary theories. The third is the fact that evolutionary speculations can be experimentally checked to a far greater extent than has been realized in the past. It is the combination of new facts, new theories, and new hopes of proof which makes this an auspicious moment to reconsider the problems of human origins. Why the matter needs reconsideration after all the mass of work done on it deserves a word...
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The complete amino acid sequences (primary structure) of hemoglobins can, in principle, be determined by methods currently available. Although detailed studies of the primary structure of human and horse hemoglobins are in progress in several laboratories,(1) the methods are so laborious that complete sequences have not yet been established. Important questions in the realm of genetics and evolution require the immediate examination of the structure, primary and other, of many different hemoglobins. The application of methods that are quicker, though less informative and reliable, than the techniques required for complete sequence determination is therefore in order as a provisional means of securing useful information. Such a method is the analysis of peptide patterns obtained by combined paper electrophoresis and chromatography of tryptic hydrolysates of denatured hemoglobin.(2) Of particular interest are comparisons between hemoglobin components present in (a) organisms of one animal species at a given time in development, (b) organisms of one species at different stages of development, and (c) organisms of different species. The present paper is concerned exclusively with the last type of comparison. In order to scan the range of variation of hemoglobin structure throughout evolution, hemoglobins from a number of animals both closely and distantly related to man have been selected and compared as to tryptic peptide patterns with human hemoglobin A. Whole hemoglobin preparations from adult animals have been studied throughout. The problem of individual heterogeneity will be treated elsewhere.
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Platinum metals are depleted in the earth's crust relative to their cosmic abundance; concentrations of these elements in deep-sea sediments may thus indicate influxes of extraterrestrial material. Deep-sea limestones exposed in Italy, Denmark, and New Zealand show iridium increases of about 30, 160, and 20 times, respectively, above the background level at precisely the time of the Cretaceous-Tertiary extinctions, 65 million years ago. Reasons are given to indicate that this iridium is of extraterrestrial origin, but did not come from a nearby supernova. A hypothesis is suggested which accounts for the extinctions and the iridium observations. Impact of a large earth-crossing asteroid would inject about 60 times the object's mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record. One prediction of this hypothesis has been verified: the chemical composition of the boundary clay, which is thought to come from the stratospheric dust, is markedly different from that of clay mixed with the Cretaceous and Tertiary limestones, which are chemically similar to each other. Four different independent estimates of the diameter of the asteroid give values that lie in the range 10 +/- 4 kilometers.