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141
Date Added: Apr 10, 2021
Authors: Hajdinjak, Mateja, et al
Date Added: Apr 10, 2021
Authors: Hajdinjak, Mateja, et al
Modern humans appeared in Europe by at least 45,000 years ago1–5, but the extent of their interactions with Neanderthals, who disappeared by about 40,000 years ago6, and their relationship to the broader expansion of modern humans outside Africa are poorly understood. Here we present genome-wide data from three individuals dated to between 45,930 and 42,580 years ago from Bacho Kiro Cave, Bulgaria1,2. They are the earliest Late Pleistocene modern humans known to have been recovered in Europe so far, and were found in association with an Initial Upper Palaeolithic artefact assemblage. Unlike two previously studied individuals of similar ages from Romania7 and Siberia8 who did not contribute detectably to later populations, these individuals are more closely related to present-day and ancient populations in East Asia and the Americas than to later west Eurasian populations. This indicates that they belonged to a modern human migration into Europe that was not previously known from the genetic record, and provides evidence that there was at least some continuity between the earliest modern humans in Europe and later people in Eurasia. Moreover, we find that all three individuals had Neanderthal ancestors a few generations back in their family history, confirming that the first European modern humans mixed with Neanderthals and suggesting that such mixing could have been common.
140
Date Added: Apr 30, 2021
Authors: Smaers, J. B., et al
Date Added: Apr 30, 2021
Authors: Smaers, J. B., et al
Relative brain size has long been considered a reflection of cognitive capacities and has played a fundamental role in developing core theories in the life sciences. Yet, the notion that relative brain size validly represents selection on brain size relies on the untested assumptions that brain-body allometry is restrained to a stable scaling relationship across species and that any deviation from this slope is due to selection on brain size. Using the largest fossil and extant dataset yet assembled, we find that shifts in allometric slope underpin major transitions in mammalian evolution and are often primarily characterized by marked changes in body size. Our results reveal that the largest-brained mammals achieved large relative brain sizes by highly divergent paths. These findings prompt a reevaluation of the traditional paradigm of relative brain size and open new opportunities to improve our understanding of the genetic and developmental mechanisms that influence brain size. An in-depth look at mammalian brain size evolution prompts a reevaluation of a traditional paradigm. An in-depth look at mammalian brain size evolution prompts a reevaluation of a traditional paradigm.
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Date Added: Jan 19, 2021
Authors: Anja Petaros, Sabrina Sholts, Mislav Čavka, Mario Slaus, Sebastian K.T.S. Wärmländer
Date Added: Jan 19, 2021
Authors: Anja Petaros, Sabrina Sholts, Mislav Čavka, Mario Slaus, Sebastian K.T.S. Wärmländer
The frontal bone is one of the sexually dimorphic elements of the human skull that can be used for sex estimation of unidentified human remains. Numerous morphological features of the frontal bone, such as its angle of inclination, maximum anterior projection (glabella), and rounded elevations (frontal eminences) have been shown to differ between males and females. Various approaches have been developed to assess the frontal inclination in particular, and recently a method has been proposed where the angle of the frontal slope is measured from snapshots of digital three-dimensional (3D) models of human crania. However, as 3D-based investigations of skeletal material can be time-consuming and expensive, we here compare measurements of frontal angle inclination from 3D model snapshots to measurements from 2D photographs for a large sample (61 females and 61 males) of dry archaeological crania from medieval Croatia. Although angles measured from 3D snapshots and 2D photographs produced discriminant functions that classified crania by sex with similar accuracy (around 73%), the angles recorded from the 2D photographs were systematically one degree smaller than the angles recorded from the 3D images. Thus, even though both data sets were useful for sex estimation, we conclude that angles measured with the two different techniques should not be combined.
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Date Added: Jan 19, 2021
Authors: Sabrina B. Sholts, Leslea J. Hlusko, Joshua P. Carlson, Sebastian K. T. S. Wärmländer
Date Added: Jan 19, 2021
Authors: Sabrina B. Sholts, Leslea J. Hlusko, Joshua P. Carlson, Sebastian K. T. S. Wärmländer
Histological analysis of teeth can yield information on an organism’s growth and development, facilitating investigations of diet, health, environment, and long-term responses to selective pressures. In the Americas, an extraordinary abundance of Late Pleistocene fossils including teeth has been preserved in petroleum seeps, constituting a major source of information about biotic changes and adaptations at the end of the last glacial period. However, the usefulness of these fossils for histological studies is unclear, due to the unknown taphonomic effects of long-term deposition in petroleum. Here, we compare histological and chemical analyses on dire wolf ( ) teeth obtained from two different environments, i.e. a petroleum seep (Rancho La Brea tar pits, California) and a carstic sinkhole (Cutler Hammock sinkhole, Florida). Optical and scanning electron microscopy (SEM) together with X-ray diffraction (XRD) analysis revealed excellent preservation of dental microstructure in the seep sample, and the petroleum-induced discoloration was found not to interfere with the histological and chemical examination. By comparison, teeth from the sinkhole sample showed severe degradation and contamination of the dentine by exogenous substances. These results indicate that petroleum seep assemblages are useful, or even ideal, environments for preserving the integrity of fossil material for chemical and histological analysis.
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Date Added: Jan 19, 2021
Authors: Anja Petaros, Sabrina B. Sholts, Mislav Čavka, Mario Slaus, Sebastian K.T.S. Wärmländer
Date Added: Jan 19, 2021
Authors: Anja Petaros, Sabrina B. Sholts, Mislav Čavka, Mario Slaus, Sebastian K.T.S. Wärmländer
3D analysis of skeletal volumes has become an important field in digital anthropology studies. The volume of the mastoid process has been proposed to display significant sexual dimorphism, but it has a complex shape and to date no study has quantified the full mastoid volume for sex estimation purposes. In this study we compared three different ways to isolate the volume of the mastoid process from digital 3D models of dry crania, and then evaluated the performance of the three different volume definitions for sex estimation purposes. A total of 170 crania (86 male, 84 females) excavated from five medieval Croatian sites were CT-scanned and used to produce 3D stereolitographic models. The three different isolation techniques were based on various anatomical landmarks and planes, as well as the anatomy of the mastoid process itself. Measurements of the three different mastoid volumes yielded different accuracies and precisions. Interestingly, anatomical structures were sometimes more useful than classical landmarks as demarcators of mastoid volume. For all three volume definitions, male mastoid volumes were significantly larger than female volumes, in both relative and absolute numbers. Sex estimation based on mastoid volume showed a slightly higher precision and better accuracy (71 % correct classifications) than visual scoring techniques (67 %) and linear distance measurements (69 %) of the mastoid process. Sex estimation based on cranial size performed even better (78 %), and multifactorial analysis (skull size + mastoid volume) reached up to 81% accuracy. These results show that measurements of the mastoid volume represent a promising metric to be used in multifactorial approaches for sex estimation of human remains.
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Date Added: Jan 19, 2021
Authors: Wärmländer, Sebastian K.T.S., et al
Date Added: Jan 19, 2021
Authors: Wärmländer, Sebastian K.T.S., et al
Chemical analysis of archeological objects can provide important clues about their purpose and function. In this study, we used scanning electron microscopy (SEM) and chemical spectroscopy (SEM-EDS and XRD) to identify a white residue present on cylindrical rhizoliths from a component at an archaeological site (CA-SNI-25) on San Nicolas Island, California, dated ca. AD 1300 to 1700. The residue was found to consist of biogenic calcite and aragonite particles, different in composition and morphology from the CaCO3 particles in the rhizoliths, but identical to marine shell material. These results, together with observations of surface micro-wear patterning on fishhooks and rhizoliths, replicative experiments, situ spatial analysis, and other archaeological evidence, show that rhizoliths were used as files in a larger tool kit for crafting shell fishhooks. Our findings shed new light on the technological innovations devised by Native Americans to exploit the rich marine resources surrounding the Channel Islands, and provide the first analytical evidence for the use of rhizoliths as a production tool.
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Date Added: May 6, 2020
Authors: Perri, Angela, et al
Date Added: May 6, 2020
Authors: Perri, Angela, et al
The domestication of dogs probably occurred in Eurasia by 16,000 years ago, with the initial peopling of the Americas potentially happening around the same time. Dogs were long thought to have accompanied the first migrations into the Americas, but conclusive evidence for Paleoindian dogs is lacking. The direct dating of two dogs from the Koster site (Greene Co., Illinois) and a newly-described dog from the Stilwell II site (Pike Co., Illinois) to between 10,190-9,630 cal BP represents the earliest evidence of domestic dogs in the Americas and individual dog burials in worldwide archaeological record. The over 4,500 year discrepancy between the timing of initial human migration into the Americas and the earliest evidence for domesticated dogs suggests either earlier dogs are going unseen or unidentified or dogs arrived later with a subsequent human migration.
0
Date Added: May 6, 2020
Authors: Crompton, Robin, et al
Date Added: May 6, 2020
Authors: Crompton, Robin, et al
StW 573, from Sterkfontein Member 2, dated ca 3.67 Ma, is by far the most complete skeleton of an australopith to date. Joint morphology is in many cases closely matched in available elements of Australopithecus anamensis (eg. proximal and distal tibial and humeral joint-surfaces) and there are also close similarities to features of the scapula, in particular, of KSD-VP-1/1 A. afarensis from Woranso-Mille. The closest similarities are, however, to the partial skeleton of StW 431 from Sterkfontein Member 4. When considered together, both StW 573 and StW 431 express an hip joint morphology quite distinct from that of A. africanus Sts14, and a proximal femur of a presumed A. africanus from Jacovec Cavern at Sterkfontein, StW 598. This, and other evidence presented herein, suggests there are two pelvic girdle morphs at Sterkfontein, supporting Clarke (2013) in his recognition of a second species, A. prometheus, containing StW 573 and StW 431. StW 573 is the first hominid skeleton where limb proportions are known unequivocally. It demonstrates that some early hominins, at the time of formation of the Laetoli footprints (3.6 Ma), were large-bodied. with hindlimbs longer than forelimbs. Modelling studies on extant primates indicate that the intermembral index (IMI) of StW 573, low for a non-human great ape, would have substantially enhanced economy of bipedal walking over medium-to-long distances, but that it was still too high for effective walking while load-carrying. It would, however, have somewhat reduced the economy of horizontal climbing, but made Gorilla-like embracing of large tree-trunks less possible. Consideration of both ethnographic evidence from modern indigenous arboreal foragers and modern degeneracy theory cautions against prescriptive interpretations of hand- and foot-function, by confirming that both human-like upright bipedalism and functional capabilities of the hand and foot can be effective in short-distance arboreal locomotion.
0
Date Added: May 6, 2020
Authors: Joanna Wolfe, Allison Daley, David Legg, Gregory Edgecombe
Date Added: May 6, 2020
Authors: Joanna Wolfe, Allison Daley, David Legg, Gregory Edgecombe
Fossil age data and molecular sequences are increasingly combined to establish a timescale for the Tree of Life. Arthropods, as the most species-rich and morphologically disparate animal phylum, have received substantial attention, particularly with regard to questions such as the timing of habitat shifts (e.g. terrestrialisation), genome evolution (e.g. gene family duplication and functional evolution), origins of novel characters and behaviours (e.g. wings and flight, venom, silk), biogeography, rate of diversification (e.g. Cambrian explosion, insect coevolution with angiosperms, evolution of crab body plans), and the evolution of arthropod microbiomes. We present herein a series of rigorously vetted calibration fossils for arthropod evolutionary history, taking into account recently published guidelines for best practice in fossil calibration. These are restricted to Palaeozoic and Mesozoic fossils, no deeper than ordinal taxonomic level, nonetheless resulting in 80 fossil calibrations for 102 clades. This work is especially timely owing to the rapid growth of molecular sequence data and the fact that many included fossils have been described within the last five years. This contribution provides a resource for systematists and other biologists interested in deep-time questions in arthropod evolution.
2
Date Added: Jan 21, 2021
Authors: Mohamad Bazzi, Nicolás Campione, Per Erik Ahlberg, Henning Blom, Benjamin Philip Kear
Date Added: Jan 21, 2021
Authors: Mohamad Bazzi, Nicolás Campione, Per Erik Ahlberg, Henning Blom, Benjamin Philip Kear
Sharks (Selachimorpha) are iconic marine predators that have survived multiple mass extinctions over geologic time. Their fossil record is represented by an abundance of teeth, which traditionally formed the basis for reconstructing large-scale diversity changes among different selachimorph clades. By contrast, corresponding patterns in shark ecology, as measured through morphological disparity, have received comparatively limited analytical attention. Here, we use a geometric morphometric approach to comprehensively examine the dental morphology of multiple shark lineages traversing the catastrophic end-Cretaceous mass extinction — this event terminated the Mesozoic Era 66 million years ago. Our results show that selachimorphs maintained virtually static levels of dental disparity in most of their constituent clades during the Cretaceous/Paleogene transition. Nevertheless, selective extinctions did impact on apex predator lineages characterized by triangular blade-like teeth, and in particular, lamniforms including the dominant Cretaceous anacoracids. Other groups, such as, triakid carcharhiniforms, squalids, and hexanchids, were seemingly unaffected. Finally, while some lamniform lineages experienced morphological depletion, others underwent a post-extinction disparity increase, especially odontaspidids, which are typified by narrow-cusped teeth adapted for feeding on fishes. This disparity shift coincides with the early Paleogene radiation of teleosts, a possible prey source, as well as the geographic relocation of shark disparity ‘hotspots’, perhaps indicating a regionally disjunct pattern of extinction recovery. Ultimately, our study reveals a complex morphological response to the end-Cretaceous mass extinction event, the dynamics of which we are only just beginning to understand.
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