Desta vez vários autores propõem-se a rever todos os dados climáticos e as datações de 14C disponíveis para a área do Levante. Para além de um evidente determinismo ambiental com o qual pretendem explicar as grandes mudanças ocorridas na região, os autores concluem que é urgente obter novas datações para alguns sítios-chave pois as que estão hoje disponíveis não podem ser consideradas válidas. Aliás, a visão que constroem com o presente artigo só foi possível excluindo inúmeras datações que consideram terem sido obtidas de forma errada e que somente provocam barulho em toda a discussão deste tema - datas descontextualizadas, com intervalos de tempo demasiado grandes ou com materiais não sujeitos aos devidos procedimentos laboratoriais. Eis os critérios utilizados na filtragem, ou melhor, na exclusão de datações:
"1. Dates where there was not secure association in the literature to the event in question,
2. Dates where we could not ascertain what material had been directly dated, this is very important given the well known problems with radiocarbon dates on mixed material.
3. Dates where we could not ascertain a likely reliable pre-treatment strategy, such as older dates on bone, where successful collagen extraction and removal of contaminants was unlikely, again this is a significant problem and the dates of poorly treated bone have been shown to be incorrect on the order of several thousand years (Jacobi and Higham, 2008).
4. Dates that were undertaken before the late 1980s where large laboratory measurement uncertainties meant that the ages were likely to cause more confusion than add value (note most of these dates were already rejected by other specific quality assurance criteria)."
Este problema deve ser entendido como crucial na interpretação de um evento tão importante como a Neolitização. Este problema é uma realidade também em Portugal, por exemplo, na datação do fenómeno Campaniforme na Estremadura portuguesa onde em alguns casos são utilizadas datas obtidas sobre carvõe de proveniência duvidosa no interior dos povoados (e.g. Penha Verde e Verdelha do Ruivos).
Fica aqui o resumo do artigo que motivou esta mensagem:
" This paper re-examines the chronology and environmental context for the transition to agriculture in the Southern Levant, seen as the likely starting point for the adoption of agriculture in Europe and the Near East. The role in this process of abrupt late Quaternary climate change has been discussed widely, but limitations on the archaeological and palaeoenvironmental chronologies have led to varying interpretations. Here we attempt to clarify the situation by first testing the available radiocarbon database for the archaeological transitions from the Natufian through to the PPNA. We apply internationally accepted radiocarbon quality assurance procedures and find that a significant number of the published dates fall bellow acceptable standards. The cleaning process significantly clarifies and constrains the reported time ranges for the Natufian, Late Natufian and PPNA. We then apply the new IntCal09 calibration curve and Bayesian calibration methods, using the archaeological phasing to constrain the data and calculate the most likely timing of the transitions between each phase. We then compare the onset and duration of archaeological phases to data representing the key Northern Hemisphere climatic transitions, using the new GICC05 Greenland Ice core timescale and the timing of transitions between wet and dry phases in the southern Levant from published high precision isotopic analyses of Speleothem data. The results of this exercise present the currently best available chronology for these events and suggest that during the second part of the Lateglacial interstadial, drying of the southern Levant may have triggered the transition to the Late Natufian, when hunter-gatherer communities resorted to a more mobile lifestyle. The Late Natufian culture appears to have disappeared from the southern Levant during the Younger Dryas, as drying intensified. There is then a gap in well dated evidence for human occupation until a reappearance of humans at the onset of the Pre-Pottery Neolithic A (PPNA) period at the beginning of the Holocene. Thus the onset of the Holocene can be hypothesised to be the driver behind the onset of the Neolithic in this region."
Referência:
Blockley SPE, Pinhasi R A revised chronology for the adoption of agriculture in the Southern Levant and the role of Lateglacial climatic change. Quaternary Science Reviews In Press, Corrected Proof:
Muy interesante. Pero no encuentro la referencia online, supongo que aún no está publicado, no?
ResponderEliminarÉ ainda uma Prova já corrigida. O melhor é esperar pela versão final.
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