Trenton W. Holliday

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

The Upper Limb of Australopithecus sediba

The evolution of the human upper limb involved a change in function from its use for both locomotion and prehension (as in apes) to a predominantly prehensile and manipulative role. Well-preserved forelimb remains of 1.98-million-year-old Australopithecus sediba from Malapa, South Africa, contribute to our understanding of this evolutionary transition. Whereas other aspects of their postcranial anatomy evince mosaic combinations of primitive (australopith-like) and derived (Homo-like) features, the upper limbs (excluding the hand and wrist) of the Malapa hominins are predominantly primitive and suggest the retention of substantial climbing and suspensory ability. The use of the forelimb primarily for prehension and manipulation appears to arise later, likely with the emergence of Homo erectus.

Species Concepts, Reticulation, and Human Evolution1

Hennig differentiated parent‐offspring, or tokogenetic, relationships among organisms within a population, which are network‐like, or reticulate, in their structure, from phylogenetic relationships between species taxa, which are hierarchical. However, some biologists have recently argued that reticulation may occur across taxa at high taxonomic levels, and Jolly, using a papionin analogy for hominin evolution, argued that fossil hominins represent a group of allotaxa that likely exhibited varying degrees of hybridization in zones of ecological overlap. Such potential reticulation among the Hominini has important implications for phylogenetic reconstruction and is likely a significant source of homoplasy in the hominin fossil record. Hybridization between taxa can lead to the merging of taxa, to the reinforcement of behavioral barriers to mating, or even to the emergence of new, hybrid species. Templeton has noted that many mammalian species appear to be grouped into higher‐level, hybridizing taxa called syngameons. Evidence for such syngameons within the Hominini is here explored in light of current species concepts.

Body proportions of circumpolar peoples as evidenced from skeletal data: Ipiutak and Tigara (Point Hope) versus Kodiak Island Inuit.

Given the well-documented fact that human body proportions covary with climate (presumably due to the action of selection), one would expect that the Ipiutak and Tigara Inuit samples from Point Hope, Alaska, would be characterized by an extremely cold-adapted body shape. Comparison of the Point Hope Inuit samples to a large (n > 900) sample of European and European-derived, African and African-derived, and Native American skeletons (including Koniag Inuit from Kodiak Island, Alaska) confirms that the Point Hope Inuit evince a cold-adapted body form, but analyses also reveal some unexpected results. For example, one might suspect that the Point Hope samples would show a more cold-adapted body form than the Koniag, given their more extreme environment, but this is not the case. Additionally, univariate analyses seldom show the Inuit samples to be more cold-adapted in body shape than Europeans, and multivariate cluster analyses that include a myriad of body shape variables such as femoral head diameter, bi-iliac breadth, and limb segment lengths fail to effectively separate the Inuit samples from Europeans. In fact, in terms of body shape, the European and the Inuit samples tend to be cold-adapted and tend to be separated in multivariate space from the more tropically adapted Africans, especially those groups from south of the Sahara.

Body Size, Body Shape, and the Circumscription of the Genus Homo

Since the 1984 discovery of the Nariokotome Homo erectus/Homo ergaster skeleton, it has been almost axiomatic that the emergence of Homo (sensu stricto) was characterized by an increase in body size to the modern human condition and an autapomorphic shift in body proportions to those found today. This was linked to a behavioral shift toward more intensive carnivory and wider ranging in the genus Homo. Recent fossil discoveries and reanalysis of the Nariokotome skeleton suggest a more complex evolutionary pattern. While early Homo tend to be larger than Australopithecus/Paranthropus, they were shorter on average than people today. Reanalysis of the Nariokotome pelvis along with the discovery of additional early and middle Pleistocene pelves indicate that a narrow bi-iliac (pelvic) breadth is an autapomorphy specific to Homo sapiens. Likewise, it appears that at least some early Homo (even those referred to H. ergaster/H. erectus) were characterized by higher humero-femoral indices than the H. sapiens average. All these data suggest a pattern of mosaic postcranial evolution in Homo with implications for the increased ranging/carnivory model of the origin of Homo as well as for which species are included within the Homo hypodigm.

A New Method for Discriminating African-American from European-American Skeletons Using Postcranial Osteometrics Reflective of Body Shape

A discriminant function analysis based on seven postcranial measurements for the metric assessment of race is presented. A sample from the Terry Collection (NMNH) was used to create independent functions for African-American males and females, and European-American males and females. The functions were tested using known forensic cases from the Maxwell Museum of Anthropology and the C.A. Pound Human Identification Laboratory. Based on the Terry Collection sample, correct classification of race for males was 87.0%, and for females 100.0%. For the independent test population, correct classification for males was 81.8%, and for females only 57.1%. The low classification for females is most likely due to sample bias.

Neandertal clavicle length

Significance Neandertal clavicle length, relative to that of modern humans, has long been considered distinctive. It has been invoked with respect to their ecogeographic body proportions, thoracic shape, scapular posture and biomechanics, temporal labyrinthine shape, and ancient DNA, as well as their trait polarities and phylogenetic status. Appropriate scaling of clavicle length to estimated body mass reveals that there is a consistent pattern of clavicle length to body mass proportions across early and recent modern humans, Neandertals, and probably most of the genus Homo. It is the relative abbreviation of Neandertal humeri, a reflection of ecogeographical body proportions and population history, that distinguishes the Neandertals from many modern humans. It is therefore inappropriate to use Neandertal clavicular length to assess their biology and evolutionary relationships. The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status.

Hominoid humeral morphology: 3D morphometric analysis.

Variation in humeral morphology among hominoids has long been recognized in relation to both phylogeny and behavior. Here, we use 3D landmark data to analyze humeral shape among hominoids, including hylobatids (n = 37), Pongo (n = 33), Homo (n = 74), Pan (n = 55), and Gorilla (n = 45) to examine the relative influence of phylogenetic history vs. locomotor adaptation on humeral shape. Principal components analysis (PCA) of Procrustes shape data derived from 19 humeral type II or type III landmarks (Bookstein, 1991) for these taxa reveals the following: PC1, which primarily reflects the humeral torsion (or lack thereof) and relative diaphyseal and epiphyseal breadths, separates the relatively narrow-shafted, small articular dimensions and low humeral torsion Hylobates, and to a lesser extent, Pongo, humeri from those of the African hominoids. PC2, which largely contrasts shafts that are posteriorly convex (high PC2 scores) with antero-posteriorly straight humeral shafts (low PC2 scores) separates Homo, who tend to have A-P straighter shafts, from the more A-P bowed humeral shafts of the apes. These shape patterns suggest that the bowed shafts of Pan, Pongo, and Gorilla (and to a lesser extent, hylobatids) are due to the fact that in each of these taxa, the humerus is a weight-bearing bone, whereas the shafts of Homo are freed from locomotion. More subtle behavioral indicators are also elucidated, whereas cluster analyses (minimum spanning tree fit to a principal coordinates [PCO] plot and UPGMA dendrogram) reveal strong phylogenetic signals in the hominoid humerus as well.

Right for the Wrong Reasons: Reflections on Modern Human Origins in the Post-Neanderthal Genome Era

The sequencing of the Neanderthal genome answered once and for all the question of whether these hominins played a role in the origins of modern humans—they did, and a majority of humans alive today retain a small portion of Neanderthal genes. This finding rejects the strictest versions of the Recent African Origin model and has been celebrated by supporters of Multiregional Evolution (MRE). However, we argue that MRE can also be rejected and that other, intermediate, models of modern human origins better represent the means by which modern humans became the only extant human species. We argue this because we reject one of the major tenets of MRE: global gene flow that prevents cladogenesis from occurring. First, using reconstructions of Pleistocene hominin census size, we maintain that populations were neither large nor dense enough to result in such high levels of gene flow across the Old World. Second, we use mammalian divergence and hybridization data to show that the emergence of Homo is recent enough that member species of this genus were unlikely to have been reproductively isolated from each other, even in the absence of the high levels of global gene flow postulated by MRE supporters.

Rabbits in the grave! Consequences of bioturbation on the Neandertal “burial” at Regourdou (Montignac-sur-Vézère, Dordogne)

The understanding of Neanderthal societies, both with regard to their funerary behaviors and their subsistence activities, is hotly debated. Old excavations and a lack of taphonomic context are often factors that limit our ability to address these questions. To better appreciate the exact nature of what is potentially the oldest burial in Western Europe, Regourdou (Montignac-sur-Vézère, Dordogne), and to better understand the taphonomy of this site excavated more than 50 years ago, we report in this contribution a study of the most abundant animals throughout its stratigraphy: the European rabbit (Oryctolagus cuniculus). In addition to questions surrounding the potential bioturbation of the sites stratigraphy, analysis of the Regourdou rabbits could provide new information on Neandertal subsistence behavior. The mortality profile, skeletal-part representation, breakage patterns, surface modification, and comparison with modern reference collections supports the hypothesis that the Regourdou rabbit remains were primarily accumulated due to natural (attritional) mortality. Radiocarbon dates performed directly on the rabbit remains give ages ranging within the second half of Marine Isotope Stage 3, notably younger than the regional Mousterian period. We posit that rabbits dug their burrows within Regourdous sedimentological filling, likely inhabiting the site after it was filled. The impact of rabbit activity now brings into question both the reliability of the archaeostratigraphy of the site and the paleoenvironmental reconstructions previously proposed for it, and suggests rabbits may have played a role in the distribution of the Neandertal skeletal remains.