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Este trabajo presenta los resultados de una investigación arqueológica conducida en la cuenca del río Cisnes (~44° S), valle que atraviesa diversos ambientes del oeste de Patagonia, desde las los límites occidentales de la estepa hasta los canales del Pacífico. Éstos se ponderan a la luz de una reconstrucción paleoambiental que se extiende desde el Pleistoceno tardío al Holoceno. Los resultados permiten interpretar distintas modalidades de aproximación al entorno, las cuales son expuestas, tanto espacial, como cronológicamente. Las unidades culturales definidas ocuparon el espacio de forma discontinua y jerarquizándolo diferencialmente en atención a la variabilidad ambiental. Correlacionamos nuestros datos con la información arqueológica disponible para la región de Aisén y áreas adyacentes. Adicionalmente, se discute el problema de la continuidad cultural y eventual interacción de los cazadores recolectores esteparios con poblaciones del área archipelágica occidental.PALABRAS CLAVES: Patagonia oeste, cazadores recolectores, paleoambiente, uso del espacio. HUNTER GATHERERS SPACE USE AND HOLOCENE PALEOENVIRONMENT IN CISNES RIVER BASIN, REGIÓN DE AISÉN, CHILEABSTRACT This paper presents results on archaeological research conducted at the Cisnes river basin (~44° S), valley which passes through several environments in western Patagonia, from the westernmost limits of the steppe to the Pacific channels. These are assessed in light of a palaeoenvironmental reconstruction spanning from the Late Pleistocene to the Holocene. Results allow interpreting different ways for approaching the environment; these are exposed both spatially and chronologically. Cultural units defined occupied the space discontinuously and ranking it differentially attending to environmental variability. We

In the highlands of southern Brazil an anthropogenitcally driven expansion of forest occurred at the expense of grasslands between 1410 and 900 cal BP, coincident with a period of demographic and cultural change in the region. Previous studies have debated the relative contributions of increasing wetter and warmer climate conditions and human landscape modifications to forest expansion, but generally lacked high resoltiuon proxies to measure these effects, or have relied on single proxies to reconstruct both climate and vegetation. Here, we develop and test a model of natural ecosystem distribution against vegetation histories, paleoclimate proxies, and the archaeological record to distinguish human from temperature and precipitation impacts on the distribution and expansion of Araucaria forests during the late Holocene. Carbon isotopes from soil profiles confirm that in spite of climatic fluctuations, vegetation was stable and forests were spatially limited to south-facing slopes in the absence of human inputs. In contrast, forest management strategies for the past 1400 years expanded this economically important forest beyond its natural geographic boundaries in areas of dense pre-Columbian occupation, suggesting that landscape modifications were linked to demographic changes, the effects of which are still visible today.

A reconstruction of past environmental change from Ecuador reveals the response of lower montane forest on the Andean flank in western Amazonia to glacial-interglacial global climate change. Radiometric dating of volcanic ash indicates that deposition occurred ~324,000 to 193,000 years ago during parts of Marine Isotope Stages 9, 7, and 6. Fossil pollen and wood preserved within organic sediments suggest that the composition of the forest altered radically in response to glacial-interglacial climate change. The presence of Podocarpus macrofossils ~1000 meters below the lower limit of their modern distribution indicates a relative cooling of at least 5°C during glacials and persistence of wet conditions. Interglacial deposits contain thermophilic palms suggesting warm and wet climates. Hence, global temperature change can radically alter vegetation communities and biodiversity in this region.