The vertebral column of the Gran Dolina-TD6 and Sima de los Huesos hominins: new remains and new results

Abstract

The Early Pleistocene Gran Dolina-TD6 and the Middle Pleistocene Sima de los Huesos (SH) sites in Atapuerca (Burgos, Spain) provide a unique fossil record of the vertebral column in genus Homo. In this paper we present vertebral remains from Gran Dolina-TD6, which comprise nine new elements and provide a general account of the spinal morphology of the SH populations and its evolutionary implications. In Gran Dolina-TD6 there are 16 vertebral fossil remains representing all anatomical regions: six cervical, six thoracic, one thoracic or lumbar and three lumbar remains), which represent a minimum of five individuals. These vertebral remains are mostly fragmentary as they have been cannibalized and most complete vertebral specimen is an adult sixth cervical vertebra which shows a very horizontal spinous process, a feature also present in the KNM-WT 15,000 C7, and which has been proposed as primitive feature. In SH, there is a minimum of 212 vertebrae preserved belonging to a minimum of 12 individuals. The spine of this population is morphologically different from both modern humans and Neandertals. The spine of the SH population shows some derived features present in Neandertals, like a reduced lumbar lordosis but also retains some primitive features like a dorso-lateral orientation (in cranial view) of the transverse process of the lumbar vertebrae, which is derived (lateral) in Neandertals. Thus, the spine of the SH population does not display the full suite of derived Neandertal features, a pattern also present in the cranium and the rest of the postcranium.