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2016, Palaeogeography, Palaeoclimatology, Palaeoecology
We report on the radioisotopic age, formation, and preservation of a late Pleistocene human footprint site in northern Tanzania on the southern shore of Lake Natron near the village of Engare Sero. Over 400 human footprints, as well as tracks of zebra and bovid, are preserved in a series of volcaniclastic deposits. Based on field mapping along with geochemical and grain-size analyses, we propose that these deposits originated as proximal volcanic material from the nearby active volcano, Oldoinyo L'engai, and were then fluvially transported to the footprint site. Stable isotope results (δ18O and δ13C) suggest that the footprints were originally emplaced on a mudflat saturated by a freshwater spring and were later inundated by the rising alkaline waters of Lake Natron. We employed the 40Ar/39Ar and 14C dating methods to investigate the age of the site and determined that the footprint level is older than 5760 ± 30 yrs. BP and younger than 19.1 ± 3.1 ka. These radioisotopic ages are supported by stratigraphic correlations with previously documented debris avalanche deposits and the stable isotope signatures associated with the most recent highstand of Lake Natron, further constraining the age to latest Pleistocene. Since modern humans (Homo sapiens) were present in Africa ca. 200 ka, Engare Sero represents the most abundant and best-preserved footprint site of anatomically modern Homo sapiens currently known in Africa. Fossil footprints are a snapshot in time, recording behavior at a specific moment in history; but the actual duration of time captured by the snapshot is often not well defined. Through analog experiments, we constrain the depositional window in which the prints were made, buried, and ultimately preserved to within a few hours to days or months.
Here we report on a Holocene inter-dune site close to Walvis Bay (Namibia) which contains exceptionally well-preserved children's footprints. The footprint surface is dated using Optically Stimulated Lumines-cence (OSL) methods to approximately 1.5 ka. These dates are compared to those obtained at nearby footprint sites and used to verify a model of diachronous footprint surfaces and also add to the archaeological data available for the communities that occupied these near-coastal areas during the Holocene. This model of diachronous footprint surfaces has implications for other soft-sediment footprint sites such as the 1.5 Ma old footprints at Ileret (Kenya). The distribution of both human and animal tracks, is consistent with the passage of small flock of small ungulates (probably sheep/goats) followed by a group of approximately 9 ± 2 individuals (children or young adults). Age estimates from the tracks suggest that some of the individuals may have been as young as five years old. Variation in track topology across this sedimentologically uniform surface is explained in terms of variations in gait and weight/stature of the individual print makers and is used to corroborate a model of footprint morphology developed at a nearby site. The significance of the site within the literature on human footprints lies in the quality of the track preservation, their topological variability despite a potentially uniform substrate, and the small size of the tracks, and therefore the inferred young age of the track-makers. The site provides an emotive insight into the life of the track-makers.
Scientific Reports
Snapshots of human anatomy, locomotion, and behavior from Late pleistocene footprints at engare Sero, tanzaniafossil hominin footprints preserve data on a remarkably short time scale compared to most other fossil evidence, offering snapshots of organisms in their immediate ecological and behavioral contexts. Here, we report on our excavations and analyses of more than 400 Late Pleistocene human footprints from engare Sero, tanzania. the site represents the largest assemblage of footprints currently known from the human fossil record in Africa. Speed estimates show that the trackways reflect both walking and running behaviors. estimates of group composition suggest that these footprints were made by a mixed-sex and mixed-age group, but one that consisted of mostly adult females. One group of similarly-oriented trackways was attributed to 14 adult females who walked together at the same pace, with only two adult males and one juvenile accompanying them. In the context of modern ethnographic data, we suggest that these trackways may capture a unique snapshot of cooperative and sexually divided foraging behavior in Late pleistocene humans. Footprints are often ephemeral but when preserved in the geological record, these ichnofossils can provide unique snapshots of the lives of ancient organisms. Fossil tracks are generated and preserved on far shorter time scales than other common forms of fossil data (e.g., skeletal fossils), leading to a distinct set of hypotheses that can be developed and tested with this form of evidence. In paleoanthropology, researchers have analyzed fossil hominin footprints through a variety of analytical approaches that address a wide range of research questions (many are reviewed by Bennett and Morse 1). Perhaps most common are analyses that derive inferences regarding hominin body size and size variation 2-4 , or foot anatomy, foot function and/or locomotion 4-17. However, since footprint assemblages typically form on short time scales, these data can also be used to infer group composition and other behaviors of individuals who must have lived on the same landscape at the same time 16,18-23. Here, we report on Late Pleistocene human footprints discovered at Engare Sero, Tanzania. While our previous publications focused on the geological context and preservation of this site 24,25 , we explore the paleoanthro-pological implications of this remarkable assemblage of more than 400 human footprints. This includes inferences regarding the body sizes, locomotor behaviors, and composition of the group of humans who generated these tracks.
2019 •
Main text of proposal for doctoral research grant from the Leakey Foundation. This grant was awarded in 2012.
Reconstructing hominin paleoecology is critical for understanding our ancestors' diets, social organizations and interactions with other animals. Most paleoecological models lack fine-scale resolution due to fossil hominin scarcity and the time-averaged accumulation of faunal assemblages. Here we present data from 481 fossil tracks from northwestern Kenya, including 97 hominin footprints attributed to Homo erectus. These tracks are found in multiple sedimentary layers spanning approximately 20 thousand years. Taphonomic experiments show that each of these trackways represents minutes to no more than a few days in the lives of the individuals moving across these paleolandscapes. The geology and associated vertebrate fauna place these tracks in a deltaic setting, near a lakeshore bordered by open grasslands. Hominin footprints are disproportionately abundant in this lake margin environment, relative to hominin skeletal fossil frequency in the same deposits. Accounting for preservation bias, this abundance of hominin footprints indicates repeated use of lakeshore habitats by Homo erectus. Clusters of very large prints moving in the same direction further suggest these hominins traversed this lakeshore in multi-male groups. Such reliance on near water environments, and possibly aquatic-linked foods, may have influenced hominin foraging behavior and migratory routes across and out of Africa. Understanding the selective forces that drove human evolutionary history requires integrating different scales of ecological information. Theories regarding how global climate change affects local environmental conditions and alters hominin land use and behavior feature prominently in paleoanthropology 1–4. Unfortunately, the fossil record typically lacks the precision to address questions of hominin paleoecology at fine temporal and spatial scales because fossil assemblages comingle remains from many thousands of years and multiple habitats. Such issues of scale make it difficult to separate biological variation within a single habitat from variation across neighboring or consecutive habitats. Fossil tracks provide a unique opportunity to closely examine species' habitat associations and behavior over very short time intervals. Tracks can form anywhere on a landscape with fine-grained sediments, typically when wetted by surface water or rainfall, increasing the cohesion of the substrate. Temporary preservation of tracks depends on how well the definition of the track is maintained as the sediment dries and hardens 5. However, long-term preservation is largely dependent on how quickly the track-bearing surface is covered by additional, protective sediments 6,7. Given that trackways are ephemeral and deteriorate quickly after formation 5,8 , groups of tracks in similar preservational states are assumed to be made either simultaneously or in very close temporal proximity to each other, possibly representing a social group. Trackways with sub-parallel alignment and minimal overlap and intersection provide further support for instantaneous track formation and group movement 9,10 , but
Os alunos com necessidades educativas especiais estão nas escolas, estão nas turmas – esse desafio foi ganho. Agora, é preciso encontrar as respostas curriculares para a sua efectiva aprendizagem nesses contextos. Retomando as questões curriculares básicas, é necessário decidir o que ensinar, para que ensinar e como ensinar estes alunos, seja no interior das salas de aula, seja em unidades inseridas na escola. A Escola Inclusiva não é apenas a escola onde estão todos os alunos: é a escola onde todos os alunos aprendem.
Nos encontramos en el viejo sur de Estados Unidos de Norteamérica en el estado de Alabama lo primero que llama mi atención en la película es la forma con la que le paga el campesino a Atticus, pago con especie, le pagaba ya sea con nueces, o algunos frutos por los servicios del abogado Es interesante ver como en aquellos tiempos en el sur de Alabama un estado bien conocido por su posición sobre la esclavitud, pasados alrededor de 60 años de la desaparición de los estados confederados aun se ven rezagos de racismo, esto se ve claro en el juicio de Tom Robinson y en algunas escenas de la película cuando se habla de la raza negra, describiéndolos como flojos, poco inteligentes, bestias, etc. aun en este mar de racismo en la antigua Alabama el abogado Atticus Finch acepta defender a un joven afroamericano en un caso donde se le acusa falsamente al joven afro de una violación que nunca paso, donde todos los blancos creen ciegamente lo que dice la joven blanca porque bueno es el sur de Estados Unidos en los 30´s que se podía esperar , Atticus quiere hacer justicia por el joven, defendiéndolo, sin importar el hecho de que sea de color Es irónico como en estos Estados que en el pasado formaron los Estados confederados de América, estados donde se aceptaba la esclavitud siguieran haciendo de las suyas décadas mas tarde los hombres de color eran libres pero si uno de ellos caía en juicio estaba condenado, aunque al jurado se le muestren pruebas, se les haga de su conocimiento que es prácticamente imposible que ocurriera un hecho y no digo por la moralidad si no por el hecho físico, esto no importa si eres una persona de color En un estado "libre" que no tenia nada de libre para la gente de color, desde el juicio donde los afroamericanos estaban en una zona donde solo estaban ellos, no había ni sillas ni nada, en el jurado pura gente blanca, etc. Me es motivador ver el personaje de Atticus Finch y llevarlo a la realidad, tratando de pensar que efectivamente en esta sociedad tan retorcida en la que vivimos hoy en día, alejados de la sensibilidad, de la compasión y de la habilidad de sentir el dolor ajeno exista gente que aun luche por traer justicia al mundo, luchar por que lo que diga nuestra constitución no sean ideales si no realidades, me llena de alegría. Esta película no solo muestra como la lucha diaria por igualdad ya sea de color o social es una intensa batalla para muchas personas, haciendo analogía con el joven blanco y su padre que no aceptaban nada de nadie pero estaban hundidos en la pobreza, el niño no traía
Lo primero que se debe hacer cuando estamos frente a un problema de física, es la de realizar una lectura rápida, para tener un panorama general, luego leer nuevamente en forma pausada, para así poder establecer cuales son las leyes físicas que nos van a servir de base para plantear el problema. Posteriormente se procede a establecer, por un lado los datos que nos da el enunciado, y por otro las incógnitas, para así de esta manera escribir las fórmulas que expresan las leyes correspondientes, y que nos ayudaran a encontrar la solución primeramente en forma literal, para luego introducir los datos numéricos, con el cuidado de colocar siempre expresado en unidades del mismo sistema de medidas. Luego de obtener el resultado numérico hay que prestar atención al grado de exactitud del mismo.
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