902 resultados para Early Animal Evolution
Resumo:
As we work our way through the latest financial crisis, politicians seem both powerless to act convincingly and unable to craft from the welter of diverse and antagonistic narratives a coherent and convincing vision of the future. In this article, we argue that a temporal lens brings clarity to such confusion, and that thinking in terms of time and reflecting on privileged temporal structures helps to highlight underlying assumptions and distinguish different narratives from one another. We begin by articulating our understanding of temporality, and we proceed to apply this to the evolution of financial practice during different historical epochs as recently delineated by Gordon (2012). We argue that the principles of finance were effectively in place by the eighteenth century and that consequent developments are best conceptualized as phases in which one particular aspect is intensified. We find that in different historical periods, the temporal intensification associated with specific models of finance shifts, over history, from the past to the present to the future. We argue that a quite idiosyncratic understanding of the future has been intensified in the present phase, what we refer to as proximal future, and we explain how this has come to be. We then consider the ethical consequences of privileging an intensification of proximal future before mapping an alternative model centred on intensifying distal future, highlighting early signs of its potential emergence in the shadows of our present.
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Chimpanzees are native only to the jungles of equatorial Africa, but for the last hundred years, they have also lived in captivity in the United States, most commonly in biomedical research laboratories, but also at Air Force bases for experiments for the space program, at accredited and unaccredited zoos, at circuses, as performers in Hollywood and even in private homes and backyards as pets. But that has been gradually evolving over the last few decades, as more and more chimpanzees move to newly-established chimpanzee sanctuaries. That transition was already underway even before the announcement by the National Institutes of Health (NIH) last year that it will retire all of its remaining chimpanzees from labs to sanctuaries. By thoroughly examining the evolution of these sanctuaries leading up to that seminal decision, along with the many challenges they face, including money, medical care, conflicting philosophies on the treatment of animals and the pitfalls that have led other sanctuaries to the brink of ruin, we can take away a better understanding of why chimpanzee sanctuaries are needed and why caretakers of other animal species are now looking to the chimpanzee sanctuary movement as a model to show how animals can be cared for in retirement.
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Neophobia, the fear of novelty, is a behavioral trait found across a number of animal species, including humans. Neophobic individuals perceive novel environments and stimuli to have aversive properties, and exhibit fearful behaviors when presented with non-familiar situations. The present study examined how early life exposure to aversive novel stimuli could reduce neophobia in bobwhite quail chicks. Experiment 1 exposed chicks to a novel auditory tone previously shown to be aversive to naïve chicks (Suarez, 2012) for 24 hours immediately after hatching, then subsequently tested them in the presence of the tone within a novel maze task. Postnatally exposed chicks demonstrated decreased fearfulness compared to naïve chicks, and behaved more similarly to chicks tested in the presence of a known attractive auditory stimulus (a bobwhite maternal assembly call vocalization). Experiment 2 exposed chicks to the novel auditory tone for 24 hours prenatally, then subsequently tested them within a novel maze task. Prenatally exposed chicks showed decreased fearfulness to a similar degree as those postnatally exposed, revealing that both prenatal and postnatal exposure methods are capable of decreasing fear of auditory stimuli. Experiment 3 exposed chicks to a novel visual stimulus for 24 hours postnatally, then subsequently tested them within a novel emergence box / T-maze apparatus. Chicks exposed to the visual stimulus showed decreased fearfulness compared to naïve chicks, thereby demonstrating the utility of this method across sense modalities. Experiment 4 assessed whether early postnatal exposure to one novel stimulus could generalize and serve to decrease fear of novelty when chicks were tested in the presence of markedly different stimuli. By combining the methods of Experiments 1 and 3, this experiment revealed that chicks exposed to one type of stimulus (auditory or visual) demonstrated decreased fear when subsequently tested in the presence of the opposite type of novel stimulus. These results suggest that experience with novel stimuli can moderate the extent to which neophobia will develop during early development.
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Evolution of the planktic foraminiferal lineage Globorotalia (Fohsella) occurred during the Miocene between 23.7 and 11.8 Ma and forms the basis for stratigraphic subdivision of the early middle Miocene (Zones N 10 through N 12). Important morphologic changes within the G. (Fohsella) lineage included a marked increase in test size, a transition from a rounded to an acute periphery, and the development of a keel in later forms. We found that the most rapid changes in morphology of G. (Fohsella) occurred between 13 and 12.7 Ma and coincided with an abrupt increase in the delta18O ratios of shell calcite. Comparison of isotopic results of G. (Fohsella) with other planktic foraminifers indicate that delta18O values of the lineage diverge from surface-dwelling species and approach deep-dwelling species after 13.0 Ma, indicating a change in depth habitat from the surface mixed layer to intermediate depth near the thermocline. Isotopic and faunal evidence suggests that this change in depth stratification was associated with an expansion of the thermocline in the western equatorial Pacific. After adapting to a deeper water habitat at 13.0 Ma, the G. (Fohsella) lineage became extinct abruptly at 11.8 Ma during a period when isotopic and faunal evidence suggest a shoaling of the thermocline. Following the extinction of G. (Fohsella), the ecologic niche of the lineage was filled by the Globorotalia (Menardella) group, which began as a deep-water form and later evolved to an intermediate-water habitat. We suggest that the evolution of G. (Fohsella) and G. (Menardella) were tightly linked to changes in the structure of the thermocline in the western equatorial Pacific.
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The Los Negritos porphyry copper deposit is located ~ 4 km to the northeast of Carmen de Andacollo Mine in the Chilean Cretaceous metallogenic belt. The mineralization is hosted in andesite of the Quebrada Marquesa Formation and a series of at least four early to intramineral porphyry intrusive rock types: plagioclase quartz biotite porphyry (P1b and P1a dated at 109.60± 0.75 Ma and 107.22± 0.40 Ma); plagioclase biotite porphyry (P2: 106.30 ± 0.47 Ma); and quartz plagioclase biotite porphyry (P3: 106.19 ± 0.42 Ma). These units are cut by late‐ to post‐mineral plagioclase‐hornblende porphyritic rocks (P4b: 106.20 ± 0.69 Ma and P4a: 106.50 ± 0.68 Ma). The earliest intrusive units (P1) were affected by an initial stage of K‐feldspar‐biotite alteration, with chalcopyrite, molybdenite (date at 108.5 ± 0.5 Ma) and gold (up to 0.11 ppm), and the surrounding volcanic host rock was overprinted by chlorite‐epidote dominated (propylitic) alteration. Subsequent to the P2 and P3 intrusion, these rocks were affected by albite and then a second stage of potassic alteration. The Ti and Ba contents in hydrothermal biotite are notably lower (typically Ti = 0.100‐0.144 a.p.f.u. and Ba = 0.001‐0.005 a.p.f.u) than in magmatic ones (generally Ti = 0.186‐0.222 a.p.f.u. and Ba = 0.014‐0.023 a.p.f.u.), and constitute an excellent discriminant of the nature of biotite. These early stages of alteration were overprinted by copper‐molybdenum bearing chlorite‐sericite alteration at 106.60 ± 0.5 Ma (Re‐Os age in molybdenite) and by quartz‐sericite‐pyrite veins (phyllic), respectively in the southwest and northeast areas. The average temperature associated with these two alteration facies is estimated around 305 °C. Weak albite‐calcite alteration, spatially associated with sulfosalts and distributed along the margins of P3, overprinted the phyllic facies. The intrusive rock units at the Los Negritos and Carmen de Andacollo deposits are geochemically classified as diorite to granodiorite with a calc‐alkaline magmatic affinity, and formed in a volcanic arc setting from partial melting of a metasomatized mantle wedge. They are interpreted to be cogenetic, and related to a common long‐lived magma chamber that emplaced during a period of tectonic inversion known as the Subhercynian, Peruvian or Pacific event.
Resumo:
Lactase persistence, the ability to digest the milk sugar lactose in adulthood, is highly associated with a T allele situated 13,910 bp upstream from the actual lactase gene in Europeans. The frequency of this allele rose rapidly in Europe after transition from hunter–gatherer to agriculturalist lifestyles and the introduction of milkable domestic species from Anatolia some 8000 years ago. Here we first introduce the archaeological and historic background of early farming life in Europe, then summarize what is known of the physiological and genetic mechanisms of lactase persistence. Finally, we compile the evidence for a co-evolutionary process between dairying culture and lactase persistence. We describe the different hypotheses on how this allele spread over Europe and the main evolutionary forces shaping this process. We also summarize three different computer simulation approaches, which offer a means of developing a coherent and integrated understanding of the process of spread of lactase persistence and dairying.
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Niche construction is the process by which organisms construct important components of their local environment in ways that introduce novel selection pressures. Lactase persistence is one of the clearest examples of niche construction in humans. Lactase is the enzyme responsible for the digestion of the milk sugar lactose and its production decreases after the weaning phase in most mammals, including most humans. Some humans, however, continue to produce lactase throughout adulthood, a trait known as lactase persistence. In European populations, a single mutation (−13910*T) explains the distribution of the phenotype, whereas several mutations are associated with it in Africa and the Middle East. Current estimates for the age of lactase persistence-associated alleles bracket those for the origins of animal domestication and the culturally transmitted practice of dairying. We report new data on the distribution of −13910*T and summarize genetic studies on the diversity of lactase persistence worldwide. We review relevant archaeological data and describe three simulation studies that have shed light on the evolution of this trait in Europe. These studies illustrate how genetic and archaeological information can be integrated to bring new insights to the origins and spread of lactase persistence. Finally, we discuss possible improvements to these models.
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Fossil associations from the middle and upper Eocene (Bartonian and Priabonian) sedimentary succession of the Pamplona Basin are described. This succession was accumulated in the western part of the South Pyrenean peripheral foreland basin and extends from deep-marine turbiditic (Ezkaba Sandstone Formation) to deltaic (Pamplona Marl, Ardanatz Sandstone and Ilundain Marl formations) and marginal marine deposits (Gendulain Formation). The micropalaeontological content is high. It is dominated by foraminifera, and common ostracods and other microfossils are also present. The fossil ichnoasssemblages include at least 23 ichnogenera and 28 ichnospecies indicative of Nereites, Cruziana, Glossifungites and ?Scoyenia-Mermia ichnofacies. Body macrofossils of 78 taxa corresponding to macroforaminifera, sponges, corals, bryozoans, brachiopods, annelids, molluscs, arthropods, echinoderms and vertebrates have been identified. Both the number of ichnotaxa and of species (e. g. bryozoans, molluscs and condrichthyans) may be considerably higher. Body fossil assemblages are comparable to those from the Eocene of the Nord Pyrenean area (Basque Coast), and also to those from the Eocene of the west-central and eastern part of South Pyrenean area (Aragon and Catalonia). At the European scale, the molluscs assemblages seem endemic from the Pyrenean area, although several Tethyan (Italy and Alps) and Northern elements (Paris basin and Normandy) have been recorded. Palaeontological data of studied sedimentary units fit well with the shallowing process that throughout the middle and late Eocene occurs in the area, according to the sedimentological and stratigraphical data.
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The study of the Upper Jurassic-Lower Cretaceous deposits (Higueruelas, Villar del Arzobispo and Aldea de Cortés Formations) of the South Iberian Basin (NW Valencia, Spain) reveals new stratigraphic and sedimentological data, which have significant implications on the stratigraphic framework, depositional environments and age of these units. The Higueruelas Fm was deposited in a mid-inner carbonate platform where oncolitic bars migrated by the action of storms and where oncoid production progressively decreased towards the uppermost part of the unit. The overlying Villar del Arzobispo Fm has been traditionally interpreted as an inner platform-lagoon evolving into a tidal-flat. Here it is interpreted as an inner-carbonate platform affected by storms, where oolitic shoals protected a lagoon, which had siliciclastic inputs from the continent. The Aldea de Cortés Fm has been previously interpreted as a lagoon surrounded by tidal-flats and fluvial-deltaic plains. Here it is reinterpreted as a coastal wetland where siliciclastic muddy deposits interacted with shallow fresh to marine water bodies, aeolian dunes and continental siliciclastic inputs. The contact between the Higueruelas and Villar del Arzobispo Fms, classically defined as gradual, is also interpreted here as rapid. More importantly, the contact between the Villar del Arzobispo and Aldea de Cortés Fms, previously considered as unconformable, is here interpreted as gradual. The presence of Alveosepta in the Villar del Arzobispo Fm suggests that at least part of this unit is Kimmeridgian, unlike the previously assigned Late Tithonian-Middle Berriasian age. Consequently, the underlying Higueruelas Fm, previously considered Tithonian, should not be younger than Kimmeridgian. Accordingly, sedimentation of the Aldea de Cortés Fm, previously considered Valangian-Hauterivian, probably started during the Tithonian and it may be considered part of the regressive trend of the Late Jurassic-Early Cretaceous cycle. This is consistent with the dinosaur faunas, typically Jurassic, described in the Villar del Arzobispo and Aldea de Cortés Fms.
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The Early Miocene Napak XV locality (ca 20.5 Ma), Uganda, has yielded an interesting assemblage of fossils, including the very well represented amphicyonid Hecubides euryodon. The remarkable find of a nearly complete mandible, unfortunately with poorly preserved dentition, together with new dental remains allow us to obtain a better idea about the morphology and variability of this species. Additionally, we describe a newly discovered mandible of Hecubides euryodon from the Grillental-VI locality (Sperrgebiet, Namibia), which is the most complete and diagnostic Amphicyonidae material found in this area. Comparisons with Cynelos lemanensis from Saint Gérand le Pouy (France), the type locality, and with an updated sample of the species of amphicyonids described in Africa leads us to validate the genus Hecubides. Hecubides would be phylogenetically related to the medium and large size species of Amphicyonidae from Africa, most of them now grouped into the genera Afrocyon and Myacyon, both endemic to this continent.
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Between 1914 and 1923, and in general during the 1910s and 1920s, important changes occurred in the Asturian press that can be seen, for example, in the type of dailies which achieved certain readership levels. The form and number of pages evolved, images became more common, so-called citizen journalism was more freely practised, and there was a trend -when there was an opportunity- towards publishing articles which involved the author travelling to distant lands. Simultaneously, the consideration of sport as a show and the treatment given to other content both helped outline a new media scenario.
Resumo:
Aims. Projected rotational velocities (ve sin i) have been estimated for 334 targets in the VLT-FLAMES Tarantula Survey that do not manifest significant radial velocity variations and are not supergiants. They have spectral types from approximately O9.5 to B3. The estimates have been analysed to infer the underlying rotational velocity distribution, which is critical for understanding the evolution of massive stars. Methods. Projected rotational velocities were deduced from the Fourier transforms of spectral lines, with upper limits also being obtained from profile fitting. For the narrower lined stars, metal and non-diffuse helium lines were adopted, and for the broader lined stars, both non-diffuse and diffuse helium lines; the estimates obtained using the different sets of lines are in good agreement. The uncertainty in the mean estimates is typically 4% for most targets. The iterative deconvolution procedure of Lucy has been used to deduce the probability density distribution of the rotational velocities. Results. Projected rotational velocities range up to approximately 450 kms-1 and show a bi-modal structure. This is also present in the inferred rotational velocity distribution with 25% of the sample having 0 <ve <100 km s-1 and the high velocity component having ve ∼ 250 km s-1. There is no evidence from the spatial and radial velocity distributions of the two components that they represent either field and cluster populations or different episodes of star formation. Be-type stars have also been identified. Conclusions. The bi-modal rotational velocity distribution in our sample resembles that found for late-B and early-A type stars.While magnetic braking appears to be a possible mechanism for producing the low-velocity component, we can not rule out alternative explanations. © ESO 2013.
Resumo:
During the epoch when the first collapsed structures formed (6<z<50) our Universe went through an extended period of changes. Some of the radiation from the first stars and accreting black holes in those structures escaped and changed the state of the Intergalactic Medium (IGM). The era of this global phase change in which the state of the IGM was transformed from cold and neutral to warm and ionized, is called the Epoch of Reionization.In this thesis we focus on numerical methods to calculate the effects of this escaping radiation. We start by considering the performance of the cosmological radiative transfer code C2-Ray. We find that although this code efficiently and accurately solves for the changes in the ionized fractions, it can yield inaccurate results for the temperature changes. We introduce two new elements to improve the code. The first element, an adaptive time step algorithm, quickly determines an optimal time step by only considering the computational cells relevant for this determination. The second element, asynchronous evolution, allows different cells to evolve with different time steps. An important constituent of methods to calculate the effects of ionizing radiation is the transport of photons through the computational domain or ``ray-tracing''. We devise a novel ray tracing method called PYRAMID which uses a new geometry - the pyramidal geometry. This geometry shares properties with both the standard Cartesian and spherical geometries. This makes it on the one hand easy to use in conjunction with a Cartesian grid and on the other hand ideally suited to trace radiation from a radially emitting source. A time-dependent photoionization calculation not only requires tracing the path of photons but also solving the coupled set of photoionization and thermal equations. Several different solvers for these equations are in use in cosmological radiative transfer codes. We conduct a detailed and quantitative comparison of four different standard solvers in which we evaluate how their accuracy depends on the choice of the time step. This comparison shows that their performance can be characterized by two simple parameters and that the C2-Ray generally performs best.
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[EN] Global warming can affect nesting success of sea turtles due to the rise of the sea level and the subsequent increased inundation or erosion of nesting beaches. Moreover, it can reduce male production to levels that can alter reproduction due to their temperature dependant sex determination (TSD). Now, mean nest temperatures all around the world predict a predominance of female hatchlings, and this trend may increase with global warming in the next decades.
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[EN] Two new 40Ar/39Ar ages (*) and previously published K/Ar ages of basaltic pillow lava flows are coeval with closely-related fossiliferous marine layers, allowing us to establish the beginning (5.8; 5.0; 4.8Ma at Ajuí, Fuerteventura Island and 4.8±0.03Ma (2?)* at Tamaraceite) and a middle stage (4.20±0.18Ma (2?)* at La Esfinge in Gran Canaria Island) of Early Pliocene marine deposits in the Canary Islands. Here the presence of tropicopolitan fossils (Megaselachus megalodon, Janthina typica) suggests the influence of a possible Central American Circumtropical Current during the Pliocene and in the North Atlantic basin.