Naturalis
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Facultad de Ciencias Naturales y Museo de la Universidad Nacional de La Plata
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Clocking the arrival of Homo sapiens in the Southern Cone of South America
(2018) Politis, Gustavo Gabriel; Prates, Luciano
El Cono Sur de Sudamérica (Argentina, Chile, Uruguay y el sureste de Brasil) fue la última masa continental colonizada por los humanos. Hasta hace poco, la discusión sobre el poblamiento de América giró en torno al debate Clovis-Primero vs. Pre-Clovis. Actualmente el eje del debate ha cambiado ya que ha sido aceptado consistentemente que hubo gente en el continente americano antes de Clovis), concentrándose en si los humanos estuvieron en el sur de la escudo glacial Laurentino/Cordillerano antes o después del comienzo de desglaciación (ca. 18-19 mil años) del Último Máximo Glacial (UMG). Sin embargo, mientras varios modelos han sido propuestos para defender la primera hipótesis, la segunda solo ha sido apoyada por reportes aislados y escasos datos. No se han propuesto modelos coherentes que integren los pocos sitios del continente que preceden el UMG. En este marco, un estudio detallado sobre el momento de llegada, así como de las secuencias de ocupación espacial del proceso de expansión, es importante para entender el patrón de colonización del Homo sapiens en América. En este capítulo se resumirán y discutirán las evidencias de algunos sitios clave del Cono Sur que datan de antes y después del comienzo de desglaciación del UMG. Presentamos una compilación de los fechados radiocarbónicos más tempranos como un proxy de la ocupación humana del Cono Sur, tanto de muestras asociadas a presencia humana (carbón, restos de fauna, etc.), como de restos óseos humanos. Basándonos en los gráficos producidos con esta base de datos, analizamos las principales tendencias cronológicas y las secuencias espaciales de la región. Finalmente, contrastamos nuestros resultados del Cono Sur con los nuevos modelos del poblamiento americano de escala continental basados en ADN antiguo.
Oral stress and paleodiet changes among hunter-gatherers from Negro River (northern Patagonia, Argentina) during the late Holocene
(2019) Flensborg, Gustavo A.; Serna, Alejandro; Prates, Luciano
The objective of this work is to evaluate temporal variation of dento-alveolar lesions in hunter-gatherer groups who inhabited the middle course of the Negro River during the late Holocene (ca. 3000-750 years BP) in order to discuss cultural practices and changes in the paleodiet. Caries, dental calculus, periodontal disease, periapical lesions, antemortem tooth loss, tooth wear, dislocation, and osteoarthrosic lesions in the temporomandibular joint were analysed. The sample is represented by 567 teeth and 547 alveoli, corresponding to 32 adult and subadult individuals, who were divided into two periods for comparative purposes: pre-1000 and post-1000 BP. The results indicate a low prevalence of oral lesions without differences between sex and age. In the pre-1000 BP period, there is a larger frequency of antemortem tooth loss, parafunctional wear of the anterior teeth, dental dislocations, and osteoarthrosis in the mandibular condyles compared with the post-1000 period. This tendency indicates that the individuals would have been exposed to greater stress in chewing. However, the variations were not significant, so there is no clear evidence of changes in the diet and particularly in carbohydrate and plant intake through the late Holocene. Severe tooth wear is the main factor that caused some pathologies (e.g., antemortem tooth loss), and limited the development of others (e.g., caries). The results obtained here agree with other microregions from northeastern Patagonia and differ from Humid Pampas, eastern Pampa-Patagonian transition, and lower course of the Negro River due to differences in carbohydrate consumption in the last ca. 1000 years BP.
La influencia de la nutrición sobre el desarrollo del cerebro: apuntes de una investigación basada en modelos experimentales y neuroimágenes
(2018) Barbeito-Andres, Jimena; González, Paula Natalia; Bernal, Valeria
La restricción nutricional está entre los factores ambientales más influyentes en el desarrollo cerebral. A continuación, nos enfocamos en las preguntas: ¿cómo afecta la malnutrición materna crónica al desarrollo del cerebro durante las etapas tempranas de la vida?, ¿en qué medida distintas regiones del cerebro son sensibles a los efectos de esta restricción nutricional? Para responder estas cuestiones presentamos un diseño de investigación basado en un modelo experimental e imágenes de alta resolución. Nuestros resultados muestran que el crecimiento del cerebro bajo condiciones de estrés nutricional está menos afectado que el crecimiento corporal y que las distintas estructuras del cerebro responden de manera diferencial ante este factor.
The pre-clovis peopling of South America
Politis, Gustavo Gabriel; Prates, Luciano
The peopling of America is perhaps one of the longest and most controversial debates in world archaeology, and South America has played a central role in this debate. There have been several competing models for the first peopling of the Americas, although except for the hypothesis of an Atlantic-Solutrean migration, there ismajor agreement among archaeologists and ancient geneticists that the first colonizers entered America from Northeastern Asia via Beringia and shorelines. South America is fundamental to this basic agreement and is considered the final step in the continents colonization. In this paper we present the corrent state of the debate about the early peopling of South America.
Hidden diversity in waterfall environments: The genus Acrorbis (Gastropoda: Planorbidae) from the Upper-Paraná Atlantic Forest
(2019) Vogler, Roberto Eugenio; Rumi Macchi Zubiaurre, Alejandra; Guzman, Leila Belén; Beltramino, Ariel Anibal; Serniotti, Enzo Noel; Ferrari, Walter; Peso, Juana Guadalupe
High-energy freshwater environments such as rapids and waterfalls in the Upper-Parana Atlantic Forest are home to highly endemic minute freshwater snails of the genus Acrorbis.
Only one species, Acrorbis petricola, is currently included within this genus, whose geographical distribution is restricted to three known populations, one in Brazil and the other two in Argentina. Because of habitat specificity and limited geographical distribution, the species is considered vulnerable in Argentina and endangered in Brazil. In this work, we identify five new populations of A. petricola in southern Upper-Parana´ Atlantic Forest, exclusively found on waterfalls from the Misiones Province, Argentina. Based on these populations and on specimens of one of the two historical populations from the Misiones Province, we explored the morphological features of shells and reproductive system of specimens from each location and provide the first molecular data on the species. We used DNA sequences from cytochrome c oxidase subunit I (COI) and 16S-rRNA genes to investigate the molecular diversity, genetic distances and genealogical relationships among populations. We verified the existence of intra- and interpopulation morphological variability, with the greatest variation being found in spire, spiral sculpture, penis sheath, flagella, prostatic diverticula and bursa copulatrix. We found interpopulation genetic diversity, with no intrapopulation variation, and identified six geographically structured genetic lineages with maximum genetic distances of up to 2.3%. Different combinations of morphological characters with the same genetic background within each locality were observed. The finding of new populations genetically differentiated not only broadens the known distribution of the species, but also illustrates that waterfall environments in the Atlantic Forest harbour a hidden diversity of Acrorbis that still remains to be discovered. This scenario suggests
a complex evolutionary history that needs to be unveiled and taken into account for future development of conservation strategies in this endemic genus.