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135,225 result(s) for "Biological Evolution"
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Human evolutionary biology
\"Wide-ranging and inclusive, this text provides an invaluable review of an expansive selection of topics in human evolution, variation and adaptability for professionals and students in biological anthropology, evolutionary biology, medical sciences and psychology. The chapters are organized around four broad themes, with sections devoted to phenotypic and genetic variation within and between human populations, reproductive physiology and behavior, growth and development, and human health from evolutionary and ecological perspectives. An introductory section provides readers with the historical, theoretical and methodological foundations needed to understand the more complex ideas presented later. Two hundred discussion questions provide starting points for class debate and assignments to test student understanding\"-- Provided by publisher.
Conceptual and statistical problems with the DEC+J model of founder-event speciation and its comparison with DEC via model selection
Phylogenese studies of geographic range evolution are increasingly using statistical model selection methods to choose among variants of the dispersal-extinction-cladogenesis (DEC) model, especially between DEC and DEC+J, a variant that emphasizes \"jump dispersal,\" or founder-event speciation, as a type of cladogenetic range inheritance scenario. Unfortunately, DEC+J is a poor model of founderevent speciation, and statistical comparisons of its likelihood with DEC are inappropriate. DEC and DEC+J share a conceptual flaw: cladogenetic events of range inheritance at ancestral nodes, unlike anagenetic events of dispersal and local extinction along branches, are not modelled as being probabilistic with respect to time. Ignoring this probability factor artificially inflates the contribution of cladogenetic events to the likelihood, and leads to underestimates of anagenetic, time-dependent range evolution. The flaw is exacerbated in DEC+J because not only is jump dispersal allowed, expanding the set of cladogenetic events, its probability relative to non-jump events is assigned a free parameter, j, that when maximized precludes the possibility of non-jump events at ancestral nodes. DEC+J thus parameterizes the mode of speciation, but like DEC, it does not parameterize the rate of speciation. This inconsistency has undesirable consequences, such as a greater tendency towards degenerate inferences in which the data are explained entirely by cladogenetic events (at which point branch lengths become irrelevant, with estimated anagenetic rates of 0). Inferences with DEC+J can in some cases depart dramatically from intuition, e.g. when highly unparsimonious numbers of jump dispersal events are required solely because j is maximized. Statistical comparison with DEC is inappropriate because a higher DEC+J likelihood does not reflect a more close approximation of the \"true\" model of range evolution, which surely must include time-dependent processes; instead, it is simply due to more weight being allocated (via j) to jump dispersal events whose time-dependent probabilities are ignored. In testing hypotheses about the geographic mode of speciation, jump dispersal can and should instead be modelled using existing frameworks for state-dependent lineage diversification in continuous time, taking appropriate cautions against Type I errors associated with such methods. For simple inference of ancestral ranges on a fixed phylogeny, a DEC-based model may be defensible if statistical model selection is not used to justify the choice, and it is understood that inferences about cladogenetic range inheritance lack any relation to time, normally a fundamental axis of evolutionary models.
The timescale of early land plant evolution
Establishing the timescale of early land plant evolution is essential for testing hypotheses on the coevolution of land plants and Earth’s System. The sparseness of early land plant megafossils and stratigraphic controls on their distribution make the fossil record an unreliable guide, leaving only the molecular clock. However, the application of molecular clock methodology is challenged by the current impasse in attempts to resolve the evolutionary relationships among the living bryophytes and tracheophytes. Here, we establish a timescale for early land plant evolution that integrates over topological uncertainty by exploring the impact of competing hypotheses on bryophyte−tracheophyte relationships, among other variables, on divergence time estimation. We codify 37 fossil calibrations for Viridiplantae following best practice. We apply these calibrations in a Bayesian relaxed molecular clock analysis of a phylogenomic dataset encompassing the diversity of Embryophyta and their relatives within Viridiplantae. Topology and dataset sizes have little impact on age estimates, with greater differences among alternative clock models and calibration strategies. For all analyses, a Cambrian origin of Embryophyta is recovered with highest probability. The estimated ages for crown tracheophytes range from Late Ordovician to late Silurian. This timescale implies an early establishment of terrestrial ecosystems by land plants that is in close accord with recent estimates for the origin of terrestrial animal lineages. Biogeochemical models that are constrained by the fossil record of early land plants, or attempt to explain their impact, must consider the implications of a much earlier, middle Cambrian–Early Ordovician, origin.
Gaining control : how human behavior evolved
'Gaining control' tells the story of how human behavioral capacities evolved from those of other animal species. Exploring what is known about the psychological capacities of other groups of animals, the authors reconstruct a fascinating history of our own mental evolution. In the book, the authors see mental evolution as a series of steps in which new mechanisms for controlling behavior develop in different species - starting with early representatives of this kingdom, and leading to a species - us - that can engage in a large number of different types of behavioral control. Key to their argument is the idea that each of these steps -- from reflexes to instincts, drives, emotions, and cognitive planning - can be seen as a novel type of psychological adaptation in which information is 'inherited' by an animal from its own behavior through new forms of learning - a form of major evolutionary transition. Thus the mechanisms that result from these steps in increasingly complex behavioral control can also be seen as the fundamental building blocks of psychology. Such a perspective on behaviour has a number of implications for practitioners in fields ranging from experimental psychology to public health. Short, provocative, and insightful, this book will be of great interest and use to evolutionary psychologists and biologists, anthropologists and the scientific community as a whole.
Building mountain biodiversity
Mountain regions are unusually biodiverse, with rich aggregations of small-ranged species that form centers of endemism. Mountains play an array of roles for Earth’s biodiversity and affect neighboring lowlands through biotic interchange, changes in regional climate, and nutrient runoff. The high biodiversity of certain mountains reflects the interplay of multiple evolutionary mechanisms: enhanced speciation rates with distinct opportunities for coexistence and persistence of lineages, shaped by long-term climatic changes interacting with topographically dynamic landscapes. High diversity in most tropical mountains is tightly linked to bedrock geology—notably, areas comprising mafic and ultramafic lithologies, rock types rich in magnesium and poor in phosphate that present special requirements for plant physiology. Mountain biodiversity bears the signature of deep-time evolutionary and ecological processes, a history well worth preserving.
Wild emmer genome architecture and diversity elucidate wheat evolution and domestication
Wheat (Triticum spp.) is one of the founder crops that likely drove the Neolithic transition to sedentary agrarian societies in the Fertile Crescent more than 10,000 years ago. Identifying genetic modifications underlying wheat’s domestication requires knowledge about the genome of its allo-tetraploid progenitor, wild emmer (T. turgidum ssp. dicoccoides). We report a 10.1-gigabase assembly of the 14 chromosomes of wild tetraploid wheat, as well as analyses of gene content, genome architecture, and genetic diversity. With this fully assembled polyploid wheat genome, we identified the causal mutations in Brittle Rachis 1 (TtBtr1) genes controlling shattering, a key domestication trait. A study of genomic diversity among wild and domesticated accessions revealed genomic regions bearing the signature of selection under domestication. This reference assembly will serve as a resource for accelerating the genome-assisted improvement of modern wheat varieties.
Thinking big : how the evolution of social life shaped the human mind
When and how did the brains of our hominin ancestors become human minds? When and why did our capacity for language or art, music and dance evolve? It is the contention of this pathbreaking and provocative book that it was the need for early humans to live in ever-larger social groups, and to maintain social relations over ever-greater distances the ability to think big that drove the enlargement of the human brain and the development of the human mind. This social brain hypothesis, put forward by evolutionary psychologists such as Robin Dunbar, one of the authors of this book, can be tested against archaeological and fossil evidence, as archaeologists Clive Gamble and John Gowlett show in the second part of Thinking Big. Along the way, the three authors touch on subjects as diverse and diverting as the switch from finger-tip grooming to vocal grooming or the crucial importance of making fire for the lengthening of the social day. Ultimately, the social worlds we inhabit today can be traced back to our Stone Age ancestors.
Phenotypes in phylogeography
Almost 30 y ago, the field of intraspecific phylogeography laid the foundation for spatially explicit and genealogically informed studies of population divergence. With new methods and markers, the focus in phylogeography shifted to previously unrecognized geographic genetic variation, thus reducing the attention paid to phenotypic variation in those same diverging lineages. Although phenotypic differences among lineages once provided the main data for studies of evolutionary change, the mechanisms shaping phenotypic differentiation and their integration with intraspecific genetic structure have been underexplored in phylogeographic studies. However, phenotypes are targets of selection and play important roles in species performance, recognition, and diversification. Here, we focus on three questions. First, how can phenotypes elucidate mechanisms underlying concordant or idiosyncratic responses of vertebrate species evolving in shared landscapes? Second, what mechanisms underlie the concordance or discordance of phenotypic and phylogeographic differentiation? Third, how can phylogeography contribute to our understanding of functional phenotypic evolution? We demonstrate that the integration of phenotypic data extends the reach of phylogeography to explain the origin and maintenance of biodiversity. Finally, we stress the importance of natural history collections as sources of high-quality phenotypic data that span temporal and spatial axes.