Multidisciplinary investigations at the Los Ajos archaeological mound complex in the wetlands of southeastern Uruguay challenge the traditional view that the La Plata basin was inhabited by simple groups of hunters and gatherers for much of the pre-Hispanic era. Here we report new archaeological, palaeoecological and botanical data indicating that during an increasingly drier mid-Holocene, at around 4,190 radiocarbon (14C) years before present (bp), Los Ajos became a permanent circular plaza village, and its inhabitants adopted the earliest cultivars known in southern South America. The architectural plan of Los Ajos during the following Ceramic Mound Period (around 3,000-500 14C yr bp) is similar to, but earlier than, settlement patterns demonstrated in Amazonia, revealing a new and independent architectural tradition for South America.

Much of the reading that we do occurs near our hands. Previous research has revealed that spatial processing is enhanced near the hands, potentially benefiting several processes involved in reading; however, it is unknown whether semantic processing-another critical aspect of reading-is affected near the hands. While holding their hands either near to or far from a visual display, our subjects performed two tasks that drew on semantic processing: evaluation of the sensibleness of sentences, and the Stroop color-word interference task. We found evidence for impoverished semantic processing near the hands in both tasks. These results suggest a trade-off between spatial processing and semantic processing for the visual space around the hands. Readers are encouraged to be aware of this trade-off when choosing how to read a text, since both kinds of processing can be beneficial for reading.

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STROMATOLITHIC AND OOLITHIC CARBONATIC AND DEFINITION OF THE ARROYO DE LA PEDRERA FORMATION (VENDÍAN?, URUGUAY). The Arroyo de la Pedrera Formation is defined as a new Vendian lithostratigraphic unit of Uruguay. The depositional systems are raade up of: (a) a shallow siliciclastic shelf formed by orthoquarzites and mudstones, grouped in the Cerros San Francisco Member; and (b) peritidal carbonates, which define the Cerro Victoria Member, whose depositional systems extends from the shallow subtidal to the supratidal. They are recognized by oolites, stromatolitic associations and scarce trace fossils. An intermitent subaerial exposition is recognized by tepee-structures, balite pseudomorphs and other features. The sediments are arranged in a shallowing-upward sequence, interrupted by tempestites, developed on a stable shelf, located on the margin of the Rio de la Plata Craton. The age of the formation is inferred by stratigraphic relationships and trace fossils. Deposition took place in a warm water environment, implying low paleolatitudes.

ResumenEn el apéndice de su articulo reciente, Bracco (2006:511-540) realiza una serie de comentarios e interpretaciones de la evidencia científica interdisciplinaria producida por nuestro equipo en el sitio de Los Ajos en el sureste de Uruguay. Entre otras cosas, Bracco nos imputa: (a) de haber retrocedido la problemática de investigación en el área veinte años atrás, (b) de desconocer los trabajos anteriores realizados en la región, (c) de forzar nuestros datos paleoambientales a la secuencia cultural, y (d) de alegar, sin evidencia, la naturaleza doméstica de los montículos durante el período Montículo Precerámico en Los Ajos. En este comentario, nosotros respondemos a las alegaciones de Bracco.