A geometric morphometric analysis of hominin upper second and third molars, with particular emphasis on European Pleistocene populations

The study of dental morphology by means of geometric morphometric methods allows for a detailed and quantitative comparison of hominin species that is useful for taxonomic assignment and phylogenetic reconstruction. Upper second and third molars have been studied in a comprehensive sample of Plio- and Pleistocene hominins from African, Asian and European sites in order to complete our analysis of the upper postcanine dentition. Intraspecific variation in these two molars is high, but some interspecific trends can be identified. Both molars exhibit a strong reduction of the distal cusps in recent hominin species, namely European Homo heidelbergensis, Homo neanderthalensis and Homo sapiens, but this reduction shows specific patterns and proportions in the three groups. Second molars tend to show four well developed cusps in earlier hominin species and their morphology is only marginally affected by allometric effects. Third molars can be incipiently reduced in earlier species and they evince a significant allometric component, identified both inter- and intraspecifically. European Middle Pleistocene fossils from Sima de los Huesos (SH) show a very strong reduction of these two molars, even more marked than the reduction observed in Neanderthals and in modern human populations. The highly derived shape of SH molars points to an early acquisition of typical Neanderthal dental traits by pre-Neanderthal populations and to a deviation of this population from mean morphologies of other European Middle Pleistocene groups.     

Hominin teeth from the early Late Pleistocene site of Xujiayao,Northern China

It is generally accepted that from the late Middle to the early Late Pleistocene (～340–90 ka BP), Neanderthals were occupying Europe and Western Asia, whereas anatomically modern humans were present in the African continent. In contrast, the paucity of hominin fossil evidence from East Asia from this period impedes a complete evolutionary picture of the genus Homo, as well as assessment of the possible contribution of or interaction with Asian hominins in the evolution of Homo sapiens and Homo neanderthalensis. Here we present a comparative study of a hominin dental sample recovered from the Xujiayao site, in Northern China, attributed to the early Late Pleistocene (MIS 5 to 4). Our dental study reveals a mosaic of primitive and derived dental features for the Xujiayao hominins that can be summarized as follows: i) they are different from archaic and recent modern humans, ii) they present some features that are common but not exclusive to the Neanderthal lineage, and iii) they retain some primitive conformations classically found in East Asian Early and Middle Pleistocene hominins despite their young geological age. Thus, our study evinces the existence in China of a population of unclear taxonomic status with regard to other contemporary populations such as H. sapiens and H. neanderthalensis. The morphological and metric studies of the Xujiayao teeth expand the variability known for early Late Pleistocene hominin fossils and suggest the possibility that a primitive hominin lineage may have survived late into the Late Pleistocene in China. Am J Phys Anthropol 156:224–240, 2015. © 2014 Wiley Periodicals, Inc.     

Task Specialization and Odor Effects on Proboscis Extension Conditioning in Bumblebees (Bombus huntii)

Workers in a social insect colony have distinct experiences that may affect their performance in a learning task. In this study using free-foraging and flight-cage bumblebee Bombus huntii colonies, the strength of olfactory proboscis extension conditioning (PEC) was affected by a bee’s task specialization as a nurse or forager and the stimulus odor. Nurses (n?=?26) learned to respond to the odors 1-hexanol and lavender, but foragers (n?=?25) had inhibited conditioning to both odors. More nurses (73 %) than foragers (48 %) had at least one conditioned response (CR), and nurses displayed significantly more CRs than foragers. As expected, a pseudoconditioned control group (n?=?9) showed very few CRs. Among bees that were given a second day of trials, nurses—but not foragers—showed modest improvement. Such strong inhibition of PEC has not been described in honeybee or bumblebee foragers. The stimulus odor also affected conditioning strength in nurses. Lavender, a familiar odor, elicited earlier and more CRs than 1-hexanol. We propose that learning floral odors in the context of foraging may inhibit PEC in bumblebee foragers, whereas exposure to odors in the honey stores may prime subsequent learning in nurses.     

Ardipithecus ramidus and the evolution of language and singing: An early origin for hominin vocal capability

In this paper we analyse the possibility that the early hominin Ardipithecus ramidus had vocal capabilities far exceeding those of any extant non-human primate. We argue that erect posture combined with changes in craniofacial morphology, such as reduced facial and jaw length, not only provide evidence for increased levels of pro-sociality, but also increased vocal ability. Reduced length of the face and jaw, combined with a flexed cranial base, suggests the larynx in this species was situated deeper in the neck than in chimpanzees, a trait which may have facilitated increased vocal ability. We also provide evidence that Ar. ramidus, by virtue of its erect posture, possessed a degree of cervical lordosis significantly greater than chimpanzees. This is indicative of increased mobility of the larynx within the neck and hence increased capacity to modulate vocalisations. In the paleoanthropological literature, these changes in early hominin skull morphology have to date been analysed in terms of a shift in mating and social behaviour, with little consideration given to vocally mediated sociality. Similarly, in the literature on language evolution there is a distinct lacuna regarding links between craniofacial correlates of social and mating systems and vocal ability. These are surprising oversights given that pro-sociality and vocal capability require identical alterations to the common ancestral skull and skeletal configuration. We therefore propose a model which integrates data on whole organism morphogenesis with evidence for a potential early emergence of hominin socio-vocal adaptations. Consequently, we suggest vocal capability may have evolved much earlier than has been traditionally proposed. Instead of emerging in the Homo genus, we suggest the palaeoecological context of late Miocene and early Pliocene forests and woodlands facilitated the evolution of hominin socio-vocal capability. We also propose that paedomorphic morphogenesis of the skull via the process of self-domestication enabled increased levels of pro-social behaviour, as well as increased capacity for socially synchronous vocalisation to evolve at the base of the hominin clade.     

Nest-specific composition of the trail pheromone of the stingless bee Trigona corvina within populations

Social insects have evolved highly developed communication systems, enabling them to coordinate complex interactions in their colonies. Pheromones play a major role in the coordination of many tasks. In Trigona corvina, a stingless bee that occurs in Central America, foragers use pheromones produced in their labial glands to scent mark solid substrates between a food source and their nest. Newly recruited bees subsequently follow these scent marks until they reach the food source. A recent study has revealed nest-specific differences in the composition of these trail pheromones in colonies of T.?corvina, suggesting that pheromone specificity may serve to avoid competition between foragers from different nests. However, the nests used in this study came from different populations and their foragers certainly never met in the field (Jarau et al., 2010). The aim of the present study was to investigate whether differences in the trail pheromones of foragers from different nests can also be found between neighbouring colonies within populations. We analysed the composition of trail pheromones from labial gland secretions extracted from workers from nine colonies collected at three different populations in Costa Rica. The differences in pheromone composition were even more distinct between neighbouring nests within a population than between nests of different populations. This finding corroborates the hypothesis that nest specificity of trail pheromones serves to communicate the location of a food source exclusively to nestmates, thereby avoiding intraspecific competition at resources. Resource partitioning by avoiding conspecific non-nestmates is particularly adaptive for aggressive bee species, such as T. corvina.     

Geometric morphometric analyses of hominid proximal femora: Taxonomic and phylogenetic considerations

The proximal femur has long been used to distinguish fossil hominin taxa. Specifically, the genus Homo is said to be characterized by larger femoral heads, shorter femoral necks, and more lateral flare of the greater trochanter than are members of the genera Australopithecus or Paranthropus. Here, a digitizing arm was used to collect landmark data on recent human (n=82), chimpanzee (n=16), and gorilla (n=20) femora and casts of six fossil hominin femora in order to test whether one can discriminate extant and fossil hominid (sensu lato) femora into different taxa using three-dimensional (3D) geometric morphometric analyses. Twenty proximal femoral landmarks were chosen to best quantify the shape differences between hominin genera. These data were first subjected to Procrustes analysis. The resultant fitted coordinate values were then subjected to PCA. PC scores were used to compute a dissimilarity matrix that was subjected to cluster analyses. Results indicate that one can easily distinguish Homo, Pan, and Gorilla from each other based on proximal femur shape, and one can distinguish Pliocene and Early Pleistocene hominin femora from those of recent Homo. It is more difficult to distinguish Early Pleistocene Homo proximal femora from those of Australopithecus or Paranthropus, but cluster analyses appear to separate the fossil hominins into four groups: an early australopith cluster that is an outlier from other fossil hominins; and two clusters that are sister taxa to each other: a late australopith/Paranthropus group and an early Homo group.     

The Impact of Subsistence Change on Mobility and Settlement Pattern in a Tropical Forest Foraging Economy: Some Implications for Archeology

I critically examine archeological presumptions that a continuum from "mobility" to "sedentism" underlies the evolutionary transition from hunting-gathering to agriculture. An ethnographic case from the Philippines shows that some foraging societies undergoing subsistence change may become more mobile as they near or cross the threshold to sedentary life. A distinction between residential and logistical mobility does not account for this finding, because the increased mobility in question has both residential and logistical demensions.     

Group recruitment in a thermophilic desert ant, Ocymyrmex robustior

Thermophilic desert ants—Cataglyphis, Ocymyrmex, and Melophorus species inhabiting the arid zones of the Palaearctic region, southern Africa and central Australia, respectively—are solitary foragers, which have been considered to lack any kind of chemical recruitment. Here we show that besides mainly employing the solitary mode of food retrieval Ocymyrmex robustior regularly exhibits group recruitment to food patches that cannot be exploited individually. Running at high speed to recruitment sites that may be more than 60 m apart from the nest a leading ant, the recruiter, is followed by a loose and often quite dispersed group of usually 2–7 recruits, which often overtake the leader, or may lose contact, fall back and return to the nest. As video recordings show the leader, while continually keeping her gaster in a downward position, intermittently touches the surface of the ground with the tip of the gaster most likely depositing a volatile pheromone signal. These recruitment events occur during the entire diurnal activity period of the Ocymyrmex foragers, that is, even at surface temperatures of more than 60 °C. They may provide promising experimental paradigms for studying the interplay of orientation by chemical signals and path integration as well as other visual guidance routines.     

Body size and body shape in early hominins - implications of the Gona Pelvis

Discovery of the first complete Early Pleistocene hominin pelvis, Gona BSN49/P27, attributed to Homo erectus, raises a number of issues regarding early hominin body size and shape variation. Here, acetabular breadth, femoral head breadth, and body mass calculated from femoral head breadth are compared in 37 early hominin (6.0-0.26 Ma) specimens, including BSN49/P27. Acetabular and estimated femoral head sizes in the Gona specimen fall close to the means for non-Homo specimens (Orrorin tugenesis, Australopithecus africanus, Paranthropus robustus), and well below the ranges of all previously described Early and Middle Pleistocene Homo specimens. The Gona specimen has an estimated body mass of 33.2 kg, close to the mean for the non-Homo sample (34.1 kg, range 24-51.5 kg, n = 19) and far outside the range for any previously known Homo specimen (mean = 70.5 kg; range 52-82 kg, n = 17). Inclusion of the Gona specimen within H. erectus increases inferred sexual dimorphism in body mass in this taxon to a level greater than that observed here for any other hominin taxon, and increases variation in body mass within H. erectus females to a level much greater than that observed for any living primate species. This raises questions regarding the taxonomic attribution of the Gona specimen. When considered within the context of overall variation in body breadth among early hominins, the mediolaterally very wide Gona pelvis fits within the distribution of other lower latitude Early and Middle Pleistocene specimens, and below that of higher latitude specimens. Thus, ecogeographic variation in body breadth was present among earlier hominins as it is in living humans. The increased M-L pelvic breadth in all earlier hominins relative to modern humans is related to an increase in ellipticity of the birth canal, possibly as a result of a non-rotational birth mechanism that was common to both australopithecines and archaic Homo.     

Occasional,obligatory, and habitual stone tool use in hominin evolution

Archeologists have long assumed that earlier hominins were obligatory stone tool users. This assumption is deeply embedded in traditional ways of describing the lithic record. This paper argues that lithic evidence dating before 1.7 Ma reflects occasional stone tool use, much like that practiced by nonhuman primates except that it involved flaked‐stone cutting tools. Evidence younger than 0.3 Ma is more congruent with obligatory stone tool use, like that among recent humans. The onset of habitual stone tool use at about 1.7 Ma appears correlated with increased hominin logistical mobility (carrying things). The onset of obligatory stone tool use after 0.3 Ma may be linked to the evolution of spoken language. Viewing the lithic evidence dating between 0.3‐1.7 Ma as habitual stone tool use explains previously inexplicable aspects of the Early‐Middle Pleistocene lithic record.     

The Atapuerca sites and their contribution to the knowledge of human evolution in Europe

Over the last two decades, the Pleistocene sites of the Sierra de Atapuerca (Spain) have provided two extraordinary assemblages of hominin fossils that have helped refine the evolutionary story of the genus Homo in Europe. The TD6 level of the Gran Dolina site has yielded about one hundred remains belonging to a minimum of six individuals of the species Homo antecessor. These fossils, dated to the end of the Lower Pleistocene (800 kyr), provide the earliest evidence of hominin presence in Western Europe. The origin of these hominins is unknown, but they may represent a speciation event from Homo ergaster/Homo erectus. The TD6 fossils are characterized by a significant increase in cranial capacity as well as the appearance of a “sapiens” pattern of craniofacial architecture. At the Sima de los Huesos site, more than 4,000 human fossils belonging to a minimum of 28 individuals of a Middle Pleistocene population (ca. 500–400 kyr) have been recovered. These hominins document some of the oldest evidence of the European roots of Neanderthals deep in the Middle Pleistocene. Their origin would be the dispersal out of Africa of a hominin group carrying Mode 2 technologies to Europe. Comparative study of the TD6 and Sima de la Huesos hominins suggests a replacement model for the European Lower Pleistocene population of Europe or interbreeding between this population and the new African emigrants.     

An analysis of a ‘community-driven’ reconstruction of the human metabolic network

Following a strategy similar to that used in baker’s yeast (Herrgård et al. Nat Biotechnol 26:1155–1160, 2008). A consensus yeast metabolic network obtained from a community approach to systems biology (Herrgård et al. 2008; Dobson et al. BMC Syst Biol 4:145, 2010). Further developments towards a genome-scale metabolic model of yeast (Dobson et al. 2010; Heavner et al. BMC Syst Biol 6:55, 2012). Yeast 5—an expanded reconstruction of the Saccharomyces cerevisiae metabolic network (Heavner et al. 2012) and in Salmonella typhimurium (Thiele et al. BMC Syst Biol 5:8, 2011). A community effort towards a knowledge-base and mathematical model of the human pathogen Salmonella typhimurium LT2 (Thiele et al. 2011), a recent paper (Thiele et al. Nat Biotechnol 31:419–425, 2013). A community-driven global reconstruction of human metabolism (Thiele et al. 2013) described a much improved ‘community consensus’ reconstruction of the human metabolic network, called Recon 2, and the authors (that include the present ones) have made it freely available via a database at http://humanmetabolism.org/ and in SBML format at Biomodels (http://identifiers.org/biomodels.db/MODEL1109130000). This short analysis summarises the main findings, and suggests some approaches that will be able to exploit the availability of this model to advantage.     

Unique Dental Morphology of Homo floresiensis and Its Evolutionary Implications

Homo floresiensis is an extinct, diminutive hominin species discovered in the Late Pleistocene deposits of Liang Bua cave, Flores, eastern Indonesia. The nature and evolutionary origins of H. floresiensis’ unique physical characters have been intensively debated. Based on extensive comparisons using linear metric analyses, crown contour analyses, and other trait-by-trait morphological comparisons, we report here that the dental remains from multiple individuals indicate that H. floresiensis had primitive canine-premolar and advanced molar morphologies, a combination of dental traits unknown in any other hominin species. The primitive aspects are comparable to H. erectus from the Early Pleistocene, whereas some of the molar morphologies are more progressive even compared to those of modern humans. This evidence contradicts the earlier claim of an entirely modern human-like dental morphology of H. floresiensis, while at the same time does not support the hypothesis that H. floresiensis originated from a much older H. habilis or Australopithecus-like small-brained hominin species currently unknown in the Asian fossil record. These results are however consistent with the alternative hypothesis that H. floresiensis derived from an earlier Asian Homo erectus population and experienced substantial body and brain size dwarfism in an isolated insular setting. The dentition of H. floresiensis is not a simple, scaled-down version of earlier hominins.     

Mass spectrometric U-series dating of Huanglong Cave in Hubei Province,central China: Evidence for early presence of modern humans in eastern Asia

Most researchers believe that anatomically modern humans (AMH) first appeared in Africa 160-190 ka ago, and would not have reached eastern Asia until ∼50 ka ago. However, the credibility of these scenarios might have been compromised by a largely inaccurate and compressed chronological framework previously established for hominin fossils found in China. Recently there has been a growing body of evidence indicating the possible presence of AMH in eastern Asia ca. 100 ka ago or even earlier. Here we report high-precision mass spectrometric U-series dating of intercalated flowstone samples from Huanglong Cave, a recently discovered Late Pleistocene hominin site in northern Hubei Province, central China. Systematic excavations there have led to the in situ discovery of seven hominin teeth and dozens of stone and bone artifacts. The U-series dates on localized thin flowstone formations bracket the hominin specimens between 81 and 101 ka, currently the most narrow time span for all AMH beyond 45 ka in China, if the assignment of the hominin teeth to modern Homo sapiens holds. Alternatively this study provides further evidence for the early presence of an AMH morphology in China, through either independent evolution of local archaic populations or their assimilation with incoming AMH. Along with recent dating results for hominin samples from Homo erectus to AMH, a new extended and continuous timeline for Chinese hominin fossils is taking shape, which warrants a reconstruction of human evolution, especially the origins of modern humans in eastern Asia.     

Environment,preferred habitats and potential refugia for Pleistocene Homo in Southeast Asia

Multiple lines of evidence suggest that Southeast Asia was dominated by a mix of savannah, open woodlands, and evergreen forests throughout much of the Pleistocene. These conditions are ideal for early hominin subsistence; however, they would have been rare for much of the rest of Asia during glacial periods. We explore the possibility that Southeast Asia would have served as a refugium for hominins during these periods. In particular, we draw parallels with the population source and sink model proposed for northern Europe (Dennell et al., 2010), with Southeast Asia acting as a population source and northern China acting as a population sink.     

Crystallographic refinement and atomic models of the intact immunoglobulin molecule Kol and its antigen-binding fragment at 3.0 Å and 1.9 Å resolution

The crystal structures of the intact immunoglobulin G1, (λ) Kol and its Fab² fragment were crystallographically refined at 3.0 Å and 1.9 Å resolution, respectively. The methods used were real space refinement (RLSP) energy and residual refinement (EREF), phase combination, constrained rigid body refinement (CORELS) and difference and Fourier map inspection. The final R-values are 0.24 and 0.26. These analyses allowed the construction of atomic models of parts not seen in detail in the previous analyses at 5 Å and 3 Å resolution, respectively (Colman et al., 1976; Matsushima et al., 1978): i.e. the hinge segment, the hypervariable segments and their intimate interaction with the hinge segment of a crystallographically related molecule.The hinge segment forms a short poly-l-proline double helix from Cys527 to Cys530 (Eu numbering 226 to 230). The preceding segment forms an open turn of helix. This segment and the segment following the poly-l-proline part, which was found to be flexible in Fc fragment crystals (Deisenhofer et al., 1976) probably allow arm and stem movement of the antibody molecule. The combining site of Kol is compared with the combining site of Fab New (Saul et al., 1978). The narrow cleft formed by the hypervariable loops in Kol is filled with aromatic amino acid side-chains. In the crystal, the hypervariable loops contact the hinge and adjacent segments of a related molecule accompanied by a substantial loss in accessible surface area. This contact is preserved in Kol Fab crystals and presumably occurs in the Kol cryoprecipitate. A comparison of the quaternary structures of intact Kol and Fab New showed, in addition to the large change in elbow angle (Colman et al., 1976), changes in lateral domain association. These are discussed in the context of a possible signal transmission from the combining site to the distal end. An attempt was made to model build the IgG3 hinge segment, which is quadruplicated with respect to IgG1 (Michaelsen et al., 1977), on the basis of the Kol hinge structure. A polyproline double helix appeared to be the most plausible model. The Fc part was found to be disordered in intact Kol crystals (Colman et al., 1976). Refinement has reduced the electron density further in the crystal space, where the Fc parts must be located. Disorder, if static, must be fourfold or more in the crystalline state.Intensity measurements on Kol F(ab′)₂ and their comparison with intact Kol crystals provide evidence that the disorder is predominantly of a static nature.     

Évolution des grands Carnivores au Plio Pléistocène en Afrique et en Europe occidentale

This paper provides an overview of current knowledge of Plio Pleistocene Carnivora from Africa and Europe. In Plio Pleistocene times, many genera extend their ranges in Africa and Eurasia but their evolution are quite distinct in the two continents. In Africa, the modern carnivoran guild of sub saharian Africa originated in the early Pleistocene when took place extinction of archaic species. The north African fossil record is far from complete until the middle Pleistocene. In the middle and late Pleistocene, the modern carnivoran guild is associated with other elements: the simian jackal Canis simensis and two species of ursids Ursus arctos and Ursus deningeri which evolved towards Ursus spelaeus. Western European carnivore faunas show due to migration a constant turn-over of the species. Among felids, Panthera schaubi described by Viret (1954) and attributed to the genus Puma by Hemmer et al. (2004), is morphologically close to the snow leopard Panthera (Uncia) uncia. Canis etruscus is the sister group pf the clade including wolf and coyote and Canis arnensis is close to the African jackals. Ursus deningeri appears in the early Pleistocene together with two arctoid forms Ursus rodei and Ursus dolinensis that may be synonymous to Ursus arctos. The genus Hyaena is present in Europe in the middle and late Pleistocene.