24 research outputs found

    The contexts and early Acheulean archaeology of the EF-HR paleo-landscape (Olduvai Gorge, Tanzania).

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    Renewed fieldwork at the early Acheulean site of EF-HR (Olduvai Gorge, Tanzania) has included detailed stratigraphic studies of the sequence, extended excavations in the main site, and has placed eleven additional trenches within an area of nearly 1 km2, to sample the same stratigraphic interval as in the main trench across the broader paleo-landscape. Our new stratigraphic work suggests that EF-HR is positioned higher in the Bed II sequence than previously proposed, which has implications for the age of the site and its stratigraphic correlation to other Olduvai Middle Bed II sites. Geological research shows that the main EF-HR site was situated at the deepest part of an incised valley formed through river erosion. Archaeological excavations at the main site and nearby trenches have unearthed a large new assemblage, with more than 3000 fossils and artefacts, including a hundred handaxes in stratigraphic position. In addition, our test-trenching approach has detected conspicuous differences in the density of artefacts across the landscape, with a large cluster of archaeological material in and around the main trench, and less intense human activity at the same level in the more distant satellite trenches. All of these aspects are discussed in this paper in the light of site formation processes, behavioral contexts, and their implications for our understanding of the early Acheulean at Olduvai Gorge

    New excavations at the HWK EE site: Archaeology, paleoenvironment and site formation processes during late Oldowan times at Olduvai Gorge, Tanzania

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    This paper reports the results of renewed fieldwork at the HWK EEsite(Olduvai Gorge, Tanzania). HWK EEis positioned across the boundary between Lower andMiddle Bed II, a crucialinterval for studyingthe emergence of the Acheulean at Olduvai Gorge. Our excavations at HWK EEhave produced one of the largest collections of fossils and artefacts from any Oldowan site, distributed across several archaeological units and a large excavation surface in four separate trenches thatcan be stratigraphically correlated. Here we present the main stratigraphic and archaeological units and discuss site formation processes.Results show a great density of fossils and stone tools vertically through two stratigraphic intervals (Lemuta and Lower Augitic Sandstone)and laterally across an area of around 300 m2, and highlight the confluence of biotic and abiotic agents in the formation of the assemblage. The large size and diversityof the assemblage, as well as its good preservation, qualify HWK EEas a reference sitefor the study of the late Oldowan at Olduvai Gorge and elsewhere in Africa. In addition, thedescriptionof the stratigraphic and archaeological sequenceof HWK EE presented in this paper constitutesthe foundation for further studies on hominin behaviour and palaeoecologyin Lower and Middle Bed II

    Nuclear Distributions of NUP62 and NUP214 Suggest Architectural Diversity and Spatial Patterning among Nuclear Pore Complexes

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    The shape of nuclei in many adherent cultured cells approximates an oblate ellipsoid, with contralateral flattened surfaces facing the culture plate or the medium. Observations of cultured cell nuclei from orthogonal perspectives revealed that nucleoporin p62 (NUP62) and nucleoporin 214 (NUP214) are differentially distributed between nuclear pore complexes on the flattened surfaces and peripheral rim of the nucleus. High resolution stimulated emission depletion (STED) immunofluorescence microscopy resolved individual NPCs, and suggested both heterogeneity and microheterogeneity in NUP62 and NUP214 immunolabeling among in NPC populations. Similar to nuclear domains and interphase chromosome territories, architectural diversity and spatial patterning of NPCs may be an intrinsic property of the nucleus that is linked to the functions and organization of underlying chromatin

    Intramolecular Cohesion of Coils Mediated by Phenylalanine–Glycine Motifs in the Natively Unfolded Domain of a Nucleoporin

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    The nuclear pore complex (NPC) provides the sole aqueous conduit for macromolecular exchange between the nucleus and the cytoplasm of cells. Its diffusion conduit contains a size-selective gate formed by a family of NPC proteins that feature large, natively unfolded domains with phenylalanine–glycine repeats (FG domains). These domains of nucleoporins play key roles in establishing the NPC permeability barrier, but little is known about their dynamic structure. Here we used molecular modeling and biophysical techniques to characterize the dynamic ensemble of structures of a representative FG domain from the yeast nucleoporin Nup116. The results showed that its FG motifs function as intramolecular cohesion elements that impart order to the FG domain and compact its ensemble of structures into native premolten globular configurations. At the NPC, the FG motifs of nucleoporins may exert this cohesive effect intermolecularly as well as intramolecularly to form a malleable yet cohesive quaternary structure composed of highly flexible polypeptide chains. Dynamic shifts in the equilibrium or competition between intra- and intermolecular FG motif interactions could facilitate the rapid and reversible structural transitions at the NPC conduit needed to accommodate passing karyopherin–cargo complexes of various shapes and sizes while simultaneously maintaining a size-selective gate against protein diffusion

    The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions

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    During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequence

    The larger mammal fossil assemblages from Beds III and IV, Olduvai Gorge, Tanzania: implications for the feeding behavior of Homo erectus

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    This dissertation represents the first taphonomically-informed assessment of the feeding behavior of Homo erectus. Until now studies of the feeding behavior of Early Stone Age hominins based on the assemblage-wide proportions of tooth, cut, and percussion marks have focused on Oldowan sites attributed to Homo habilis leaving assessments of the subsistence capabilities of Homo erectus to inference. This trend is the direct result of the river/channel depositional settings for most sites that are attributed to Homo erectus and the lack of a theoretically-grounded basis for interpreting fossil assemblages from such sites. Using a flume I have generated the first experimental sample designed to interpret bone assemblages that were modified by hominins and carnivores and subsequently disturbed by flowing water. Results show that the transportability of bone fragments is inversely related to the size of bone fragments as measured by length, width, cortical thickness, and indirectly by the size group of the carcass from which the fragments were generated. More importantly, fluvial processes should not significantly alter the assemblage-wide proportions of tooth, cut, and percussion marks in low-energy fluvial environments. The results of flume experiments are applied here in the first taphonomic analysis of the larger mammal fossil assemblages from JK2, Bed III and WK, Bed IV, Olduvai Gorge, Tanzania. The results for both sites indicate that Homo erectus likely acquired earlier access to carcasses than its Oldowan hominin ancestors. However, only the younger WK site exhibits evidence for cooking indicating that the feeding behavior of the species was continually evolving. The significance of this research lies not only in the results reported for the Bed III and IV fossil assemblages, but also in the methodology that was developed to interpret the results, which is broadly applicable to archaeological sites regardless of age or geographic location. Further application of these methods will allow paleoanthropologists to track the increasingly pervasive role played by Homo erectus in the larger carnivore guild. For it is through this research that the social behavior of the species may ultimately be revealed and a greater understanding of our own behavior and societies can be obtained.Ph.D.Includes bibliographical referencesIncludes vitaby Michael C. Pant

    The paleoecology of Pleistocene birds from Middle Bed II, at Olduvai Gorge, Tanzania, and the environmental context of the Oldowan-Acheulean transition

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    Fossil bird data (community composition and taphonomic profiles) are used here to infer the environmental context of the Oldowan-Acheulean transitional period at Olduvai Gorge, Tanzania. This is the first comprehensive report on the Middle Bed II avifauna and includes fossils excavated by the Olduvai Geochronology and Archaeology Project (OGAP) and recently rediscovered fossils collected by Mary Leakey. Crane, ibis, darter, owl, raptor, crow, and vulture are reported from Bed II for the first time. The presence of these taxa, absent earlier in this Bed, point to a general opening and drying of the landscape with grassland and open woodland expansion. Taxa associated with dense, emergent wetland vegetation, such as dabbling ducks and rails, are uncommon and less diverse than earlier in Bed II. This suggests more mature wetlands with clearer waters. Cormorants continue to be common, but are less diverse. Cormorants and other roosting taxa provide evidence of trees in the area. Compared to lowermost Bed II, the Middle to Upper Bed II landscape is interpreted here as more open and drier (but not necessarily more arid), with matured wetlands, scattered trees, and a greater expansion of grasslands

    New excavations in the MNK Skull site, and the last appearance of the Oldowan and Homo habilis at Olduvai Gorge, Tanzania

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    MNK Skull is one of the most significant archaeological sites in Olduvai Gorge, particularly due to the previous discovery of human fossils referred to in the paper where the Homo habilis taxon was originally defined. An important archaeological assemblage is contained in the same horizon as the hominin fossils, constituting the last evidence of both Homo habilis remains and handaxe-free tool kits in the Olduvai Gorge sequence. Our excavations at the site are the first to be conducted since the original work in the 1960s, and sought to refine the archaeological context wherein the Homo habilis remains were discovered. Chronostratigraphic results place the MNK Skull sequence in Middle Bed II prior to deposition of Tuff IIB. The assemblage was deposited near the shoreline, as Palaeolake Olduvai withdrew into the basinal depocentre, and fossils and stone tools were subjected to significant post-depositional processes. The assemblage was affected by mudflow deposits that buried and preserved the assemblage but also entrained surficial bone and lithic elements into the flow. Rather than an occupation site as originally interpreted, the assemblage is better understood as a background deposit, possibly accumulated on an unconformity surface over a long period of time. The stone tool assemblage is typical of the Oldowan, with no technological elements announcing the appearance of the Acheulean, which is well attested to across the Olduvai sequence in post-Tuff IIB times. Our results highlight that, with an approximate age of circa 1.67 Ma, MNK Skull stands as a key site to understand the late Oldowan and the disappearance of Homo habilis in East Africa.Peer reviewe

    Don't cry over spilled ink: Missing context prevents replication and creates the Rorschach effect in bone surface modification studies

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    The scientific replicability crisis has recently focused on bone surface modification (BSM) analysis, which underlies zooarchaeological and anthropological conclusions about the ecology and evolution of tool-assisted carcass consumption behavior. We review a recent blind test of inter-analyst correspondence in morphometric analysis of experimentally generated butchery marks that advocates algorithmic methods for diagnosing and measuring BSM in an effort to standardize methodology and minimize inter-analyst error (Domínguez-Rodrigo et al. 2017. Use and abuse of cut mark analyses: The Rorschach effect. Journal of Archaeological Science, 86, 14–23. https://doi.org/10.1016/j.jas.2017.08.001). This study overstates concern about the inaccuracy of BSM measurement and interpretation, concluding that BSM analysis is a subjective, non-scientific endeavor. Based on a minimally described sample of cut marks, it measures variables that involve inherent inaccuracy and subjectivity and overlooks how the contexts of experimental sample generation – particularly the difference between immanent and configurational processes – differentially affect cut mark morphometrics. We illustrate this discussion with experimental taphonomic examples focused on analytical context including sample construction and control over factors that affect cut mark cross-sectional size. Our analysis suggests the relationship between tool attributes and cut mark morphology is not generalizable to all experimental and archaeological butchery contexts. We show that our experimental samples capture metric variability observed in archaeological cut marks, but that intentionally incised marks and realistic defleshing marks differ in width and depth. Further, when controlling for factors that impact cut mark size including animal size class, tool type, butcher experience, and density across bone portions, overlapping cut mark widths and depths produced by phonolite and ignimbrite flakes lead to poor classification of marks according to causal flake material, which casts doubt on the ability to discriminate cut marks made by different materials. We build datasets that include diverse experimental contexts and suggest that meta-analysis can disentangle how multiple configurational factors contribute to cut mark morphometric attributes. Ultimately, progress in BSM analysis rests on inter-analyst replicability, which must be preceded by clear discussion of all parts of the inferential loop – from the design of experiments that generate actualistic analogues, to their use in supporting archaeological arguments. Otherwise, problematic expert knowledge traditions may mask arguments from authority in sophisticated methodological language and under-reported experimental context

    Dietary traits of the ungulates from the HWK EE site at Olduvai Gorge (Tanzania): Diachronic changes and seasonality

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    The Oldowan site HWK EE (Olduvai Gorge, Tanzania) has yielded a large fossil and stone tool assemblage at the transition from Lower to Middle Bed II, ∼1.7 Ma. Integrated tooth wear and stable isotope analyses were performed on the three most abundant ungulate taxa from HWK EE, namely Alcelaphini, cf. Antidorcas recki (Antilopini) and Equus oldowayensis (Equini), to infer dietary traits in each taxon. Some paleodietary changes were observed for cf. A. recki and E. oldowayensis based on tooth wear at the transition from the Lemuta to the Lower Augitic Sandstone (LAS) interval within the HWK EE sequence. Stable carbon and oxygen isotope data show no significant changes in bulk diet or hydroclimate between the Lemuta and LAS intervals. The combined tooth wear and stable isotope data suggest similar paleoecological conditions across the two HWK EE intervals, but that differences in vegetation consumed among ungulates may have resulted in changes in dietary niches. Integrating tooth wear and stable isotope analyses permits the characterization of ungulate diets and habitats at HWK EE where C4_4 dominated and minor mixed C3_3 and C4_4 habitats were present. Our results provide a better understanding of the paleoenvironmental conditions of the Lemuta and LAS intervals. The LAS assemblage was mostly accumulated during relatively dry periods at Olduvai Gorge when grasses were not as readily available and grazing animals may have been more nutritionally-stressed than during the formation of the Lemuta assemblage. This helps to contextualize variations in hominin and carnivore feeding behavior observed from the faunal assemblages produced during the two main occupations of the site
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