The Cranium I: Neurocranium

The Sima de los Huesos (SH) site has provided a significant collection of hominin remains, including numerous cranial fragments, which have contributed to our understanding of the MP human population. The taxonomic classification of the SH hominins remains a topic of debate, with some studies suggesting a close relationship to Neandertals based on nuclear DNA analysis. The cranial morphology of the SH specimens exhibits a mix of Neandertal-like features and primitive traits observed in earlier Homo populations, providing insights into the evolutionary pattern of the Neanderthal lineage. This study focuses on the neurocranial traits of the SH population and describes three previously undescribed cranial individuals. The SH cranial collection now comprises 20 nearly complete crania, representing approximately two-thirds of the estimated population size. The analysis of the SH population reveals variations in robustness, frontal torus development, sagittal keeling, and occipital torus morphology, which may be related to sexual dimorphism and ontogenetic factors. The suprainiac region exhibits notable ontogenetic changes, while suture obliteration patterns do not strictly correlate with dental age. Metric measurements, particularly cranial breadths, highlight significant intrapopulation variation within the SH sample. Compared with other Middle Pleistocene (MP) hominins, the SH cranial vault displays archaic characteristics but differs from Homo erectus and Neandertals. The SH individuals have relatively short and tall cranial vaults, distinguishing them from other MP fossils. These findings contribute to our understanding of the MP human populations and their evolutionary trajectories.

A virtual assessment of the suprainiac depressions on the Eyasi I (Tanzania) and Aduma ADU-VP-1/3 (Ethiopia) Pleistocene hominin crania

Despite a steady increase in our understanding of the phenotypic variation of Pleistocene Homo, debate continues over phylogenetically informative features. One such trait is the suprainiac fossa, a depression on the occipital bone above inion that is commonly considered an autapomorphy of the Neanderthal lineage. Challenging this convention, depressions in the suprainiac region have also been described for two Pleistocene hominin crania from sub-Saharan Africa: Eyasi I (Tanzania) and ADU-VP-1/3 (Ethiopia). Here, we use a combined quantitative and qualitative approach, using μCT imaging, to investigate the occipital depressions on these specimens. The results show that neither the external nor the internal morphologies of these depressions bear any resemblance to the Neanderthal condition. A principal component analysis based on multiple thickness measurements along the occipital squama demonstrates that the relative thickness values for the internal structures in Eyasi I and ADU-VP-1/3 are within the range of Homo sapiens. Thus, our results support the autapomorphic status of the Neanderthal suprainiac fossa and highlight the need to use nuanced approaches and multiple lines of evidence.

The endocast of the late Middle Paleolithic Manot 1 specimen, Western Galilee, Israel

Studying endocasts has long allowed anthropologists to examine changes in the external topography and the overall size of the brain throughout the evolutionary history of hominins. The nearly complete calvaria of Manot 1 presents an opportunity to gain insights into the external brain morphology, vascular system, and dimensions of the brain of this late Middle Paleolithic hominin. Detailed size and shape analyses of the Manot 1 endocast indicate a modern Homo sapiens anatomy, despite the presence of some primitive features of the calvaria. Traits considered to be derived endocranial features for H. sapiens are present in Manot 1, including an elongated parietal sagittal chord with an elevated superior part of the hemisphere, a widened posterior part of the frontal lobes, a considerable development of the parietal reliefs such as the supramarginal lobules, and a slight posterior projection of the occipital lobes. These findings, together with data presented in previous studies, rule out the possibility of a direct Neanderthal ancestry for the Manot 1 hominin and instead confirm its affiliation with H. sapiens. The Manot 1 calvaria is more similar to that of later Upper Paleolithic H. sapiens than it is to the earlier Levantine populations of Skhul and Qafzeh. The late Middle Paleolithic date of Manot 1 provides an opportunity to analyze the recent developments in human cerebral morphology and organization.

Neandertal-like traits visible in the internal structure of non-supranuchal fossae of some recent Homo sapiens: The problem of their identification in hominins and phylogenetic implications

Although recently the internal structure of the non-supranuchal fossa of Homo sapiens has been described and compared to that observed in the Neandertal suprainiac fossa, until now it has not been examined in any modern human children. In this study, the internal structure of this fossa in the occipital bones of three children (two aged 3‒4 years and one aged 5 years ± 16 months) and one adult individual representing recent Homo sapiens from Australia was analysed and compared to that of the Neandertal suprainiac fossa. In order to analyse the internal composition of the fossae of the examined specimens, initially, high-resolution micro-CT datasets were obtained for their occipital bones; next, 3D topographic maps of the variation in thickness of structural layers of the occipital bones were made and 2D virtual sections in the median region of these fossae were prepared. In the fossa of one immature individual, the thinning of the diploic layer characteristic of a Neandertal suprainiac fossa was firmly diagnosed. The other Neandertal-like trait, concerning the lack of substantial thinning of the external table of the bone in the region of the fossa, was established in two individuals (one child and one adult) due to the observation of an irregular pattern of the thickness of this table in the other specimens, suggesting the presence of an inflammatory process. Our study presents, for the first time, Neandertal-like traits (but not the whole set of features that justifies the autapomorphic status of the Neandertal supraniac fossa) in the internal structure of non-supranuchal fossae of some recent Homo sapiens. We discuss the phylogenetic implications of the results of our analysis and stress the reasons that use of the 3D topographic mapping method is important for the correct diagnosis of Neandertal traits of the internal structure of occipital fossae.

Brain, calvarium, cladistics: A new approach to an old question, who are modern humans and Neandertals?

The evolutionary history of the genus Homo is the focus of major research efforts in palaeoanthropology. However, the use of palaeoneurology to infer phylogenies of our genus is rare. Here we use cladistics to test the importance of the brain in differentiating and defining Neandertals and modern humans. The analysis is based on morphological data from the calvarium and endocast of Pleistocene fossils and results in a single most parsimonious cladogram. We demonstrate that the joint use of endocranial and calvarial features with cladistics provides a unique means to understand the evolution of the genus Homo. The main results of this study indicate that: (i) the endocranial features are more phylogenetically informative than the characters from the calvarium; (ii) the specific differentiation of Neandertals and modern humans is mostly supported by well-known calvarial autapomorphies; (iii) the endocranial anatomy of modern humans and Neandertals show strong similarities, which appeared in the fossil record with the last common ancestor of both species; and (iv) apart from encephalisation, human endocranial anatomy changed tremendously during the end of the Middle Pleistocene. This may be linked to major cultural and technological novelties that had happened by the end of the Middle Pleistocene (e.g., expansion of the Middle Stone Age (MSA) in Africa and Mousterian in Europe). The combined study of endocranial and exocranial anatomy offers opportunities to further understand human evolution and the implication for the phylogeny of our genus.

La Ferrassie 8 Neandertal child reloaded: New remains and re-assessment of the original collection

The first evidence of the partial infant Neandertal skeleton La Ferrassie 8 (LF8) was discovered in 1970, although most of the remains were found in 1973 as part of the 1968-1973 work at the site by H. Delporte. This individual and the other Neandertal children from La Ferrassie were published in the early 1980s by J.-L. Heim, and since then LF8 has been regarded as coming from a poorly documented excavation. The recent rediscovery of the box that contained the hominin bones given by Delporte to Heim in the Muséum national d'Histoire naturelle (MNHN) collection provided new fossils and helped to locate LF8 in the site: level M2 in square 1. Two visits to the Musée d'Archéologie nationale et Domaine national de Saint-Germain-en-Laye (MAN) yielded additional fossil remains from both the 1970 and 1973 excavations and resulted in the discovery of all of the notes from the excavation of H. Delporte between 1968 and 1973. Here the new fossil remains (47 after performing all possible refits), representing significant portions of the cranium, mandible, and vertebral column together with fragmentary hand and costal remains, are described. Unsurprisingly, the morphology of the bony labyrinth and of a complete stapes from the nearly complete left temporal show clear Neandertal affinities. Additionally, a complete reassessment of the original LF8 collection has resulted in the identification of several errors in the anatomical determination. Despite the significant increase in the anatomical representation of LF8, the skeletal remains are still limited to the head, thorax, pelvis, and four hand phalanges, with some very fragile elements relatively well preserved. Different hypotheses are proposed to explain this anatomical representation, which can be tested during future fieldwork.