Main anatomical characteristics of the hominin fossil humeri from the Sima de los Huesos Middle Pleistocene site, Sierra de Atapuerca, Burgos, Spain: An update

Abstract

Some of the Sima de los Huesos (SH) humeri have been previously studied and described elsewhere. Here we present an updated inventory and a review of the specimens recovered to the present day. The morphological key traits of the adult and subadult specimens are described, discussed, and illustrated. The SH humeri share with Neandertals many traits usually considered to be Neandertal specializations, thus, most of this morphological pattern is not exclusive to them. The variation found within fossil samples stresses the frequential nature of all these traits and in the specific case of the SH humeri, most of the traits considered as phylogenetically relevant are retained by their descendants, the Neandertals. Some traits are plesiomorphic for the entire genus Homo or are present in European hominins since the early Pleistocene. Finally, some other traits display high variability within the SH sample or different hominin samples and are of uncertain phylogenetic value. Altogether, this evidence is consistent with the hypothesis based on the overall cranial and postcranial morphology that the SH hominins are a sister group to the later Neandertals.

Fusion of the occipitomastoidal synchondrosis as a developmental marker in the Sima de los Huesos Crania (Atapuerca, Spain)

“…Although the SH fossils were originally assigned to the species Homo heidelbergensis , this assignment was withdrawn by Arsuaga et al (2014) and currently the fossils remain unattributed to any known human species (Arsuaga et al, 2014). Beyond taxonomic issues, the study of the SH human fossils has revealed the presence of numerous traits throughout the skeleton that are shared with Neanderthal populations (Arsuaga et al, 1991(Arsuaga et al, , 1993(Arsuaga et al, , 2014(Arsuaga et al, , 2015Bermúdez de Castro et al, 2019;Bermúdez De Castro & Rosas, 2001;Carretero et al, 2024;Conde-Valverde et al, 2024;Quam et al, 2024). This anatomical evidence is consistent with the results of nuclear DNA analysis, which also point to a clear relationship between the SH hominins and Neanderthals (Meyer et al, 2016).…”

Exploring the morphology of adult tibia and fibula from Sima de los Huesos site in sierra de Atapuerca, Burgos, Spain

“…Regarding the tibia, proximal and distal epiphysis are bigger than modern humans and similar to those of Neandertals. Thus, it looks like the large articulations that characterize the Neandertals are already present in those Middle Pleistocene populations and in the whole skeleton, as was settled in Arsuaga et al (2015) and other papers in this present volume (Carretero et al, 2024a(Carretero et al, , 2024bGarcía-Gonz alez et al, 2024;Rodríguez et al, 2024).…”

Updated study of adult and subadult pectoral girdle bones from Sima de los Huesos site (Sierra de Atapuerca, Burgos, Spain). Anatomical and age estimation keys

“…The pooled sex-weighted mean body mass estimated from five adult SH femoral heads is 69.1 kg, which is only 6.3 kg below the Neandertal mean (75.4 kg) (Arsuaga et al, 2015). The present sample of humeri from SH indicates that, on average, they were above the values that characterized the later Neandertals (Carretero, García-Gonz alez, Rodríguez, & Arsuaga, 2023). Thus, based on these data, the most parsimonious hypothesis is that SH hominins do not share short humeri with Neandertals.…”

“…In the SH, three complete adult humeri, sexed as males, have been recovered (Carretero et al, 2012). The maximum length is quite variable among the three complete SH specimens, ranging from 318 mm (H-X) to 345 mm (H-II and H-XV) (Carretero et al, 2023, this special issue). As mentioned above, the SGF height variation range can be interpreted as a pattern of sexual dimorphism.…”