The first human fossil from the Ruidera site (Castilla-La Mancha, Spain): A partial parietal and its implications for Middle Pleistocene hominin variability in Southern Europe.

We report a new Middle Pleistocene paleoanthropological locality located in southern Iberian Peninsula, Ruidera, and describe a newly discovered partial parietal bone (RVH-1). The fossil was chronologically constrained through a combination of uranium-series and optically stimulated luminescence dating methods. In particular, the human fossil-bearing breccia may be tentatively dated to between 224 ± 14 ka and 160 ± 10 ka, although an older age cannot be entirely excluded, given the inherent uncertainty in the gamma dose rate evaluation. When considering these new results together with those previously obtained on Caprinae fossil teeth from that same layer, we can reasonably propose a late (second half) Middle Pleistocene age for the Ruidera fossil locality. Morphological analysis shows that RVH-1 exhibits relatively high cranial vault thickness and parietal angle compared with Iberian Middle Pleistocene samples such as the preneanderthals from Sima de los Huesos from Atapuerca (Spain). However, both variables fall within the broader range of variation observed across Homo heidelbergensis (both s.l. and s.s.). In this context, RVH-1 appears to be closer to specimens often described as more plesiomorphic in Europe (e.g., Ceprano) and to some African Middle Pleistocene individuals (e.g., Kabwe). These results highlight the considerable variability in cranial morphology during the Middle Pleistocene and caution against strong taxonomic or phylogenetic interpretations based on isolated traits. RVH-1 is therefore best interpreted within a framework of morphological variability in Europe. RVH-1 provides a critical addition to the European human fossil record, which remains very fragmented for the Middle Pleistocene.