The child who lived: Down syndrome among Neanderthals?

Caregiving for disabled individuals among Neanderthals has been known for a long time, and there is a debate about the implications of this behavior. Some authors believe that caregiving took place between individuals able to reciprocate the favor, while others argue that caregiving was produced by a feeling of compassion related to other highly adaptive prosocial behaviors. The study of children with severe pathologies is particularly interesting, as children have a very limited possibility to reciprocate the assistance. We present the case of a Neanderthal child who suffered from a congenital pathology of the inner ear, probably debilitating, and associated with Down syndrome. This child would have required care for at least 6 years, likely necessitating other group members to assist the mother in childcare.

How the Sima de los Huesos was won.

Although the first discovery of a human fossil in the Sima de los Huesos took place in 1976, systematic excavations did not begin there until 1984. Since then, this site has been continuously excavated in month-long camps. The site is dated by different radiometric techniques to between 430,000 and 300,000 years ago. Until the 2023 campaign, just over 7000 human fossils have been recovered, constituting the largest collection of fossils prior to Homo sapiens ever discovered. The fossils correspond to a minimum of 29 individuals of both sexes and different ages at death, from preadolescents to a specimen of advanced age. Comparative anatomy and ancient DNA studies both suggest that this is a population closely related to Homo neanderthalensis. The great variety and extraordinary quality of the fossils recovered have allowed us to carry out a series of investigations that have greatly increased our knowledge about the evolution of Homo in the Middle Pleistocene. Among the most important discoveries, it has been possible to establish body size and proportions, the confirmation that the origin of the accumulation of human fossils was of an anthropic nature, that those past humans took care of disabled individuals and who were capable of having an oral language almost as complex and efficient as that of our own species.

Main morphological characteristics and sexual dimorphism of hominin adult femora from the Sima de los Huesos Middle Pleistocene site (Sierra de Atapuerca, Spain).

The excellent fossil record from Sima de los Huesos (SH) includes three well-known complete adult femora and several partial specimens that have not yet been published in detail. This fossil record provides an opportunity to analyze the morphology of European pre-Neandertal adult femur and its variation with different evolution patterns. Currently, there are a minimum of five adult individuals (males or females). In this study, we compiled previously published basic anatomical and biometric characteristics of SH adult femora, emphasizing the most relevant features compared to other recent and fossil hominins. The SH femora exhibited a primitive morphological pattern common to all non-Homo sapiens femora, as well as most of the Neandertal traits. Therefore, the complete Upper Pleistocene Neandertal pattern was well-established in Middle Pleistocene ancestors long before the proper Neandertals appeared. Additionally, we highlight that the SH and Neandertal femora share some morphological traits and proportions with modern humans that hold sexual significance in our species, regardless of size. Keeping this in mind, we discussed the sex determination of the complete SH specimens and re-evaluated sex allocation in two of them.

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

The analysis of the locomotor anatomy of Late Pleistocene Homo has largely focused on changes in proximal femur and pelvic morphologies, with much attention centered on the emergence of modern humans. Although much of the focus has been on changes in the proximal femur, some research has also been conducted on tibiae and, to a lesser extent, fibulae. With this in mind, we present one of the largest samples of the same population of human tibiae and fibulae from the Middle Pleistocene to determine their main characteristic traits and establish similarities and differences, primarily with those of Neanderthals and modern humans, but also with other Middle Pleistocene specimens in the fossil record. Through this study, we established that the Middle Pleistocene population from the Sima de los Huesos (Atapuerca, Burgos, Spain) had lower leg long bones similar to those of Neanderthals, although there were some important differences, such as bone length, which this fossil individuals resembled those of modern humans and not to Neanderthals. This fact is related to the crural index and leg length, even though we do not have any true association between femora and tibiae yet, it has implications for establishing locomotor efficiency and climate adaptation.

Uncovering the adult morphology of the forearm bones from the Sima de los Huesos Site in Atapuerca (Spain), with comments on biomechanical features.

The forearm skeleton is composed of two bones: the radius and the ulna. This is closely related to manipulative movements. The ulna is part of the elbow joint, whereas the radius and ulna together with the scaphoid and lunate bones, form the wrist joints. Thus, morphofunctional analysis of the adult Sima de los Huesos (SH) forearm bones, provides clues about manipulative activities in one Pleistocene population. From 1976 to the present, over 7000 human fossils have been recovered from the SH site. The radial sample comprised 98 labeled fragments, of which 49 belonged to adult individuals, representing at least 7 individuals. The ulnar sample included 31 labeled adult fossils representing at least nine individuals. In this study, we describe the SH radii and ulnae and analyze their functional implications for manipulative and forearm movements. We confirmed that the SH radii are long and curved, with variations in robusticity and radial tuberosity orientation. The SH ulnae are characterized by an anteriorly oriented trochlear notch, a massive olecranon process, an obliquely oriented radial notch, a blunt and short supinator crest, a gracile and curved diaphysis, and a round and anteriorly oriented pronator crests. In general, they exhibit Neanderthal morphology. The SH collection provides a unique opportunity to conduct morphological analyses of these bones in the Middle Pleistocene population.

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

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.

Taphonomic skeletal disturbances in the Sima de los Huesos postcranial remains.

The postcranial skeleton of fossil hominins is crucial for reconstructing the processes that occurred between the time of death and the recovery of the bones. Thousands of postcranial skeletal fragments from at least 29 hominin individuals have been recovered from the Sima de los Huesos Middle Pleistocene site in Spain. This study's primary objective is to address the main taphonomic features of the postcranial remains from the Sima de los Huesos sample, including antemortem, perimortem, and postmortem skeletal disturbances. We present an updated assessment of the bone surface modification analysis, the fracture pattern analysis, and the skeletal part representation to facilitate interpretation of the biostratinomic and fossil-diagenetic processes in this large paleoanthropological collection. We conclude that carnivores (probably bears) had limited access to the hominin bones and complete bodies were probably placed in the site.

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.

Here we present an updated inventory and study of pectoral girdle remains recovered from the Sima de los Huesos (SH) site. Here, we describe the key morphological traits of adults and, for the first time, subadult specimens. Because morphological traits can change with age, we also discuss some shortcomings related to age estimation in postcranial fossil specimens. Adult clavicles from the SH are long with a low robusticity index and marked curvatures in the superior view. Among these traits, only extreme clavicular length seems to characterize subadult individuals. Neandertals share all these traits. In the case of the scapula, the SH specimens share a relatively long and narrow glenoid fossa with Neandertals. This trait is also present in subadult individuals. Additionally, most specimens from SH, adults, and subadults showed a dorsal axillary sulcus on the scapular lateral border, a trait also present in most adult and subadult Neandertals. These traits in adult and subadult specimens supports substantial genetic control for many of them in both human species.

Dairying, diseases and the evolution of lactase persistence in Europe.

In European and many African, Middle Eastern and southern Asian populations, lactase persistence (LP) is the most strongly selected monogenic trait to have evolved over the past 10,000 years1. Although the selection of LP and the consumption of prehistoric milk must be linked, considerable uncertainty remains concerning their spatiotemporal configuration and specific interactions2,3. Here we provide detailed distributions of milk exploitation across Europe over the past 9,000 years using around 7,000 pottery fat residues from more than 550 archaeological sites. European milk use was widespread from the Neolithic period onwards but varied spatially and temporally in intensity. Notably, LP selection varying with levels of prehistoric milk exploitation is no better at explaining LP allele frequency trajectories than uniform selection since the Neolithic period. In the UK Biobank4,5 cohort of 500,000 contemporary Europeans, LP genotype was only weakly associated with milk consumption and did not show consistent associations with improved fitness or health indicators. This suggests that other reasons for the beneficial effects of LP should be considered for its rapid frequency increase. We propose that lactase non-persistent individuals consumed milk when it became available but, under conditions of famine and/or increased pathogen exposure, this was disadvantageous, driving LP selection in prehistoric Europe. Comparison of model likelihoods indicates that population fluctuations, settlement density and wild animal exploitation-proxies for these drivers-provide better explanations of LP selection than the extent of milk exploitation. These findings offer new perspectives on prehistoric milk exploitation and LP evolution.