Eva POZA-REY,Juan Luis ARSUAGA

Centro de Investigación (UCM-ISCIII) sobre la Evolución, y Comportamiento Humanos, Madrid 28029 Spain

ABSTRACT: Modern technologies based in the acquisition of images and virtual reconstruction of fossils, have allowed for the study of virtual brain endocasts of the most completed crania of the Sima de los Huesos sample, such as Cranium 5 (the most complete specimen in the human fossil record) and Cranium 4 (lacking the face). They are dated to the European Middle Pleistocene and have been compared with other European, Asian and African Pleistocene individuals. Eighteen measurements were considered during a complete metric analysis. In this present work, values obtained for both SH cranium 4 and 5 are available, to facilitate the data for further studies. The results indicate allometry is responsible for the different shape observed between SH 4 and SH 5. The lower volume of the brain endocast in specimen 5 shows limited frontal development but is structurally taller. The European Homo heidelbergensis specimens and the Neanderthals show many common features, but some differences with African Middle Pleistocene individuals. This result confirms European Homo heidelbergensis as a chronospecies of Neanderthals. Many divergences in endocasts dimensions have been found in contemporary groups around 500 ky from Asia and Europe, so the most likely fact is that the initial differences in brain dimensions occurred in earlier populations that occupied Europe at the end of the Lower Pleistocene or the beginning of the Middle Pleistocene. The physical differences that are observed between Homo heidelbergensis and the contemporary Homo erectus brains seem to demonstrated a complex social organization in the former group, and may reflect the care of older and sick specimens in the same clan. Finally, taking into account the complex behaviour of several dimensions in the brain endocasts considered in this work and the dependency-independency establishes among them along development, we suggest that studies that analyze the form (shape and size) of brain endocasts must consider this complexity, and results are not always due to size and the encephalization process.