Markus Bastir

Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa

Homo naledi is a previously-unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Cradle of Humankind, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations but a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including Homo erectus, Homo habilis or Homo rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike foot and lower limb. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, pelvis and proximal femur. Representing at least 15 individuals with most skeletal elements repeated multiple times, this is the largest assemblage of a single species of hominins yet discovered in Africa. DOI: http://dx.doi.org/10.7554/eLife.09560.001

Craniofacial levels and the morphological maturation of the human skull

It is well known that the human skull achieves adult size through a superior–inferior gradient of maturation. Because the basicranium matures in size before the face, it has been suggested that the form of the basicranium might have ontogenetic knock‐on effects on that of the face. However, although sequential spatially organized maturation of size is well described in the cranium, the maturation of skull shape is not. Knowledge of the maturation of shape is important, nevertheless, because it is claimed that the early determination of the spatial configuration of basicranial components, where the facial skeleton attaches, is relevant in the spatio‐temporal ontogenetic cascade from basicranium to face. This paper examines the ontogeny of various components of the human skull in 28 individuals from the longitudinal Denver Growth Study. Sixty‐six landmarks and semilandmarks were digitized on 228 X‐rays and analysed using geometric morphometric methods. Bootstrapped confidence intervals for centroid size support previous studies suggesting a supero‐inferior gradient of growth maturation (size over time), while developmental maturation (shape over time) is more complex. A sequence of shape maturation is described, in which the earliest structure to mature in shape was the midline cranial base (7–8 years), followed by the lateral cranial floor (11–12), midline neurocranium (9–10) and facial and mandibular structures (15–16). The absolute ages of shape maturation of the latter three depended on the criterion of maturity used, which was not the case for the basicranial components. Additionally, ontogenetic dissociations were found between the maturation of size and shape of the midline cranial base and lateral floor, possibly underlining its role as structural ‘interface’ between brain and facial ontogeny. These findings imply potential for bidirectional developmental influences between the lateral cranial floor and the face until about 11–12 years. The findings are discussed with regard to their relevance for palaeoanthropology and especially the evolutionary and developmental bases of skull morphological variation.

A new early Pleistocene hominin mandible from Atapuerca-TD6, Spain

We present the description of a new mandibular specimen, ATD6-113, recovered in 2006 from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. A detailed study of the lithostratigraphy of the top sequence of this level, the section from where all human remains have been recovered so far, is also presented. We have observed that the hominin stratum, previously defined as Aurora Stratum, represents a condensed deposit of at least six layers, which could not be distinguished in the test pit made in 1994-95. Therefore, the human fossil remains were probably deposited during a discrete and undetermined time period. The new mandibular fragment exhibits a very similar morphology to that of the most complete specimen, ATD6-96, which was recovered in 2003 from a different layer. This suggests that both specimens represent the same biological population. The two mandibles, as well as the small mandibular fragment ATD6-5 (which constitutes part of the holotype of Homo antecessor), present a morphological pattern clearly derived with regard to that of the African early Homo specimens usually included in H. habilis and H. rudolfensis, the mandibles D211 and D2735 from Dmanisi, and most of the early Pleistocene mandibles from Sangiran. The TD6 mandibles also exhibit some derived features with regard to the African early Pleistocene specimens included in H. ergaster (or African H. erectus). Thus, the TD6 hominins seem to represent a lineage different from other African and Asian lineages, although some (metric in particular) similarities with Chinese middle Pleistocene mandibles are noted. Interestingly, none of the apomorphic mandibular features of the European middle and early late Pleistocene hominins are present in the TD6 mandibles.

Genetic evidence for patrilocal mating behavior among Neandertal groups

The remains of 12 Neandertal individuals have been found at the El Sidrón site (Asturias, Spain), consisting of six adults, three adolescents, two juveniles, and one infant. Archaeological, paleontological, and geological evidence indicates that these individuals represent all or part of a contemporaneous social group of Neandertals, who died at around the same time and later were buried together as a result of a collapse of an underground karst. We sequenced phylogenetically informative positions of mtDNA hypervariable regions 1 and 2 from each of the remains. Our results show that the 12 individuals stem from three different maternal lineages, accounting for seven, four, and one individual(s), respectively. Using a Y-chromosome assay to confirm the morphological determination of sex for each individual, we found that, although the three adult males carried the same mtDNA lineage, each of the three adult females carried different mtDNA lineages. These findings provide evidence to indicate that Neandertal groups not only were small and characterized by low genetic diversity but also were likely to have practiced patrilocal mating behavior.

Effects of brain and facial size on basicranial form in human and primate evolution

Understanding variation in the basicranium is of central importance to paleoanthropology because of its fundamental structural role in skull development and evolution. Among primates, encephalisation is well known to be associated with flexion between midline basicranial elements, although it has been proposed that the size or shape of the face influences basicranial flexion. In particular, brain size and facial size are hypothesized to act as antagonists on basicranial flexion. One important and unresolved problem in hominin skull evolution is that large-brained Neanderthals and some Mid-Pleistocene humans have slightly less flexed basicrania than equally large-brained modern humans. To determine whether or not this is a consequence of differences in facial size, geometric morphometric methods were applied to a large comparative data set of non-human primates, hominin fossils, and humans (N=142; 29 species). Multiple multivariate regression and thin plate spline analyses suggest that basicranial evolution is highly significantly influenced by both brain size and facial size. Increasing facial size rotates the basicranium away from the face and slightly increases the basicranial angle, whereas increasing brain size reduces the angles between the spheno-occipital clivus and the presphenoid plane, as well as between the latter and the cribriform plate. These interactions can explain why Neanderthals and some Mid-Pleistocene humans have less flexed cranial bases than modern humans, despite their relatively similar brain sizes. We highlight that, in addition to brain size (the prime factor implicated in basicranial evolution in Homo), facial size is an important influence on basicranial morphology and orientation. To better address the multifactorial nature of basicranial flexion, future studies should focus on the underlying factors influencing facial size evolution in hominins.

Facial ontogeny in Neanderthals and modern humans

One hundred and fifty years after the discovery of Neanderthals, it is held that this morphologically and genetically distinct human species does not differ from modern Homo sapiens in its craniofacial ontogenetic trajectory after the early post-natal period. This is striking given the evident morphological differences between these species, since it implies that all of the major differences are established by the early post-natal period and carried into adulthood through identical trajectories, despite the extent to which mechanical and spatial factors are thought to influence craniofacial ontogeny. Here, we present statistical and morphological analyses demonstrating that the spatio-temporal processes responsible for craniofacial ontogenetic transformations differ. The findings emphasize that pre-natal as well as post-natal ontogeny are both important in establishing the cranial morphological differences between adult Neanderthals and modern humans.

Middle Cranial Fossa Anatomy and the Origin of Modern Humans

Anatomically, modern humans differ from archaic forms in possessing a globular neurocranium and a retracted face and in cognitive functions, many of which are associated with the temporal lobes. The middle cranial fossa (MCF) interacts during growth and development with the temporal lobes, the midface, and the mandible. It has been proposed that evolutionary transformations of the MCF (perhaps from modification of the temporal lobes) can have substantial influences on craniofacial morphology. Here, we use three-dimensional (3D) geometric morphometrics and computer reconstructions of computed tomography-scanned fossil hominids, fossil and recent modern humans and chimpanzees to address this issue further. Mean comparisons and permutation analyses of scaled 3D basicranial landmarks confirm that the MCF of Homo sapiens is highly significantly different (P < 0.001) from H. neanderthalensis, H. heidelbergensis, and Pan troglodytes. Modern humans have a unique configuration with relatively more anterolateral projection of the MCF pole relative to the optic chiasm and the foramen rotundum. These findings are discussed in the context of evolutionary changes in craniofacial morphology and the origins of modern human autapomorphies. In particular, the findings of this study point to variations in the temporal lobe, which, through effects on the MCF and face, are central to the evolution of modern human facial form.

Mitochondrial DNA of an Iberian Neandertal suggests a population affinity with other European Neandertals

Document S1. Supplemental Experimental proceduresxDownload (.04 MB ) Document S1. Supplemental Experimental procedures

Common Features of Sexual Dimorphism in the Cranial Airways of Different Human Populations

Sexual dimorphism in the human craniofacial system is an important feature of intraspecific variation in recent and fossil humans. Although several studies have reported different morphological patterns of sexual dimorphism in different populations, this study searches for common morphological aspects related to functional anatomy of the respiratory apparatus. 3D geometric morphometrics were used to test the hypothesis that due to higher daily energy expenditure and associated greater respiratory air consumption as well as differences in body composition, males should have absolutely and relatively greater air passages in the bony cranial airways than females. We measured 25 3D landmarks in five populations (N = 212) of adult humans from different geographic regions. Male average cranial airways were larger in centroid sizes than female ones. Males tended to show relatively taller piriform apertures and, more consistently, relatively taller internal nasal cavities and choanae than females. Multivariate regressions and residual analysis further indicated that after standardizing to the same size, males still show relatively larger airway passages than females. Because the dimensions of the choanae are limiting factors for air transmission towards the noncranial part of the respiratory system, the identified sex-specific differences in cranial airways, possibly shared among human populations, may be linked with sex-specific differences in body size, composition, and energetics. These findings may be important to understanding trends in hominin facial evolution.

A geometric-morphometric study of the cretan humerus for sex identification

Various scholars have pioneered sex assessment from different parts of the skeleton based on metrical or qualitative morphological characteristics. Lately though, a new technique which combines both traditional methods is becoming popular in forensic anthropology. Geometric-morphometrics is a field of multivariate statistical biometric analysis which allows the quantification of the shape and size components of morphological variation. The purpose of this investigation is to assess sex from the humerus in a contemporary Greek population using geometric-morphometric analysis of shape data derived from digital radiographs. The study population consists of 97 well-preserved adult humeri from two cemeteries of Heraklion, Crete. The left humeri are radiographed using digital radiograph machine (TCA 4R PLUS). Assuming fragmentary patterns, the proximal and distal ends are studied separately. Five landmarks are selected on the radiograph of the proximal epiphysis and seven landmarks on the distal. Generalised Procrustes analysis (GPA) and thin-plate splines are used to obtain the shape and size variables for statistical analysis. Then three discriminant function analyses were carried out: one uses the PC scores from Procrustes shape space, the second the centroid size alone and the third the PC scores of GPA residuals plus lnCS for analysis in Procrustes form space. Results indicate the existence of shape differences between the sexes. In females the greater tubercle is smoother, with its superior border less pronounced. Additionally, females have a relatively squared distal epiphysis, while males exhibit a more rectangular shape. Shape differences between genders, for the cross-validated data, give slightly better classification results in the proximal humerus (73%) compared with the distal humerus (71%). Size alone performed better (86.5% for proximal and 85.6% for distal humerus). As anticipated, the classification accuracy improves (89.6% for proximal and 89.7% for distal epiphysis) when both size and shape are combined. From the forensic standpoint, the usefulness of this study rests on the identification of sex based on shape differences observed on radiographs of fragmentary humeri that could not be assessed with traditional methods. The analysis of humeral radiographs by geometric-morphometric techniques offers an alternative way to identify the sex of unknown skeletal remains. Whether this is statistically better than simply using traditional osteometric methods is a question that needs to be tested in a meta-statistical approach.