1,721,129 research outputs found
Uniforum: Evolution des modernen Menschen der Gattung Homo
No full textDer Vortrag stammt aus der Studium Generale Reihe der Universität Tübingen vom Sommersemster 2013 zum Thema "Schlüsselereignisse der
organismischen Makroevolution". Mit der Bezeichnung Makroevolution ist keine eigengesetzliche Makroevolution, sondern eine abstrahierende, verallgemeinernde Betrachtung größerer Evolutionsabläufe gemeint. Im Sinne der Darwinschen Evolutionstheorie und der „modern synthesis“ wird die Auffassung vertreten, dass der eigentliche Evolutionsprozess mikroevolutiver
Natur ist, indem aus variierenden Populationen in jeder Generation die Bestangepassten selektiert werden. Die eigentliche Evolution ereignet sich also in kleinen Generationenschritten; die Makroevolution ist demnach eine Summation dieser kleinen Anpassungsschritte – also ein nahezu graduierlich erscheinender Prozess, der in tausenden von Generationen und in geologischen Zeiträumen zu einer allmählichen
adaptiven Veränderung der Organismen führt. Der Begriff des „Schlüsselereignisses“ macht nur im methodischen Kontext einer makroevolutiven Betrachtungsweise Sinn: Es handelt sich um tiefgreifende Veränderungen in der Konstruktion und Funktion von Organismengruppen, die in der Regel mit dramatischen Änderungen der Ökologie und der Lebensweise verknüpft sind. Umgekehrt können aber auch Umkonstruktionen der Körperorganisation in Verbindung mit Funktionswechseln ganz neuartige Lebensräume erschließen helfen. Der Begriff „organismisch“ bezieht sich auf die Erkenntnis, dass zentraler Bezugspunkt der Evolutionsbiologie der lebende Organismus sein muss, der aber immer als Teil einer Fortpflanzungsgemeinschaft (Population, Art) zu verstehen ist. Der lebende Organismus verkörpert eine ganze
Lebensgeschichte (Ontogenese), die nach Möglichkeit als Ganzes zu berücksichtigen ist. Katerina Harvati spricht in ihrem Vortrag nicht nur über den Weg und die Vorfahren des Menschen, sondern auch über neueste Erkenntnisse aus der Paläoanthropologie
Frontal bone virtual reconstruction and geometric morphometric analysis of the mid-Pleistocene hominin KNM-OG 45500 (Olorgesailie, Kenya)
Get PDFKNM-OG 45500 is a hominin fossil composed of parts of a frontal bone, left temporal bone, and cranial vault pieces. Since its discovery along the Olorgesailie Formation (Kenya) in 2003, it has been associated with the Homo erectus hypodigm. The specimen, derived from a geological context dated to ca. 900 Ka BP, has been described as a very small individual of probable female sex. However, despite its status as an important hominin specimen, it has not been used in a quantitative comparative framework because of its fragmentary condition. Here, we undertake a virtual reconstruction of the better-preserved fragment, the frontal bone. We additionally apply geometric morphometric analyses, using a geographically diverse fossil and modern human sample, in order to investigate the morphological affinities of KNM-OG 45500. Our results show that the frontal shape of KNM-OG 45500 exhibits similarities with Early Pleistocene fossils from Eurasia and Africa that are assigned to H. erectus sensu lato (s.l.). Its size, on the other hand, is notably smaller than most other Homo erectus fossils and modern humans and similar to the specimens from Dmanisi (Georgia) and to Homo naledi. Taken together, our analyses of the frontal bone suggest a taxonomic attribution of KNM-OG 45500 to H. erectus s.l. and extend even further the range of size variability associated with this taxon around 900 Ka BP
Genomic validation of the differential preservation of population history in modern human cranial anatomy
No full textObjectives: In modern humans, the significant correlation between neutral genetic loci and cranial anatomy suggests that the cranium preserves a population history signature. However, there is disagreement on whether certain parts of the cranium preserve this signature to a greater degree than other parts. It is also unclear how different quantitative measures of phenotype affect the association of genetic variation and anatomy. Here, we revisit these matters by testing the correlation of genetic distances and various phenotypic distances for ten modern human populations. Materials and Methods: Geometric morphometric shape data from the crania of adult individuals (n = 224) are used to calculate phenotypic PST, Procrustes, and Mahalanobis distances. We calculate their correlation to neutral genetic distances, FST, derived from single nucleotide polymorphisms (SNPs). We subset the cranial data into landmark configurations that include the neurocranium, the face, and the temporal bone in order to evaluate whether these cranial regions are differentially correlated to neutral genetic variation. Results: Our results show that PST, Mahalanobis, and Procrustes distances are correlated with FST distances to varying degrees. They indicate that overall cranial shape is significantly correlated with neutral genetic variation. Of the component parts examined, PST distances for both the temporal bone and the face have a stronger association with FST distances than the neurocranium. When controlling for population divergence time, only the whole cranium and the temporal bone have a statistically significant association with FST distances. Discussion: Our results confirm that the cranium, as a whole, and the temporal bone can be used to reconstruct modern human population history
Human population dynamics in Upper Paleolithic Europe inferred from fossil dental phenotypes
No full textDespite extensive archaeological research, our knowledge of the human population history of Upper Paleolithic Europe remains limited, primarily due to the scarce availability and poor molecular preservation of fossil remains. As teeth dominate the fossil record and preserve genetic signatures in their morphology, we compiled a large dataset of 450 dentitions dating between similar to 47 and 7 thousand years ago (ka), outnumbering existing skeletal and paleogenetic datasets. We tested a range of competing demographic scenarios using a coalescent-based machine learning Approximate Bayesian Computation (ABC) framework that we modified for use with phenotypic data. Mostly in agreement with but also challenging some of the hitherto available evidence, we identified a population turnover in western Europe at similar to 28 ka, isolates in western and eastern refugia between similar to 28 and 14.7 ka, and bottlenecks during the Last Glacial Maximum. Methodologically, this study marks the pioneering application of ABC to skeletal phenotypes, paving the way for exciting future research avenues
Geometric morphometric analysis and internal structure measurements of the Neanderthal lower fourth premolars from Kalamakia, Greece
No full textThis study investigates two Neanderthal lower fourth premolars from Kalamakia, Greece, in order to better explore and document the morphology of the Kalamakia assemblage. The material consisted of micro-CT scans of the Kalamakia premolars (KAL6 and KAL9), and a comparative sample of 51 specimens, including 10 Neanderthals, one early Homo sapiens, and 40 recent Homo sapiens. The premolars were analyzed applying geometric morphometric methods on crown outlines as well as collecting measurements on internal dental structures. Data were subjected to principal components and other standard statistical analyses. A between-group principal components analysis of the outline shape coordinates separated our Neanderthal sample from the modern human one with little overlap. KAL9 showed the most extreme Neanderthal shape while KAL6 fell within the NEA shape range. Additional measurements of internal structures, especially the lateral dentine and pulp chamber volume, strengthened these results
Using elliptical best fits to characterize dental shapes
No full textA variety of geometric morphometric methods have recently been used to describe dental shape variation in human evolutionary studies. However, the applicability of these methods is limited when teeth are worn or are difficult to orient accurately. Here we show that elliptical best fits on outlines of dental tissues below the crown provide basic size- and orientation-free shape descriptors. Using the dm2 and M3 as examples, we demonstrate that these descriptors can be used for taxonomic purposes, such as distinguishing between Neanderthal and recent modern human teeth. We propose that this approach can be a useful alternative to existing methodology
Reconstructing human population history from dental phenotypes
No full textAbstractDental phenotypic data are often used to reconstruct biological relatedness among past human groups. Teeth are an important data source because they are generally well preserved in the archaeological and fossil record, even when associated skeletal and DNA preservation is poor. Furthermore, tooth form is considered to be highly heritable and selectively neutral; thus, teeth are assumed to be an excellent proxy for neutral genetic data when none are available. However, to our knowledge, no study to date has systematically tested the assumption of genetic neutrality of dental morphological features on a global scale. Therefore, for the first time, this study quantifies the correlation of biological affinities between worldwide modern human populations, derived independently from dental phenotypes and neutral genetic markers. We show that population relationship measures based on dental morphology are significantly correlated with those based on neutral genetic data (on average r = 0.574, p < 0.001). This relatively strong correlation validates tooth form as a proxy for neutral genomic markers. Nonetheless, we suggest caution in reconstructions of population affinities based on dental data alone because only part of the dental morphological variation among populations can be explained in terms of neutral genetic differences.</jats:p
Functional adaptations and muscle attachment (entheseal) patterns in the hands of apes, humans, and hominins
Get PDFThe human hand, a tool of utmost importance in our everyday activities, is markedly distinct from other extant and fossil primates. The evolution of hand bone morphology, how it was used in manipulative and locomotor activities, and the emergence of human-like hand use are therefore of great interest to Paleoanthropologists. This dissertation aims to contribute to our growing knowledge about isolated and associated hand bones of hominids and hominins. It contains three case studies applying virtual methods to analyze the morphology of hand bones with a particular focus on functional morphology. The first case study focuses on an intermediate phalanx associated with the Miocene ape Ouranopithecus macedoniensis. The specimen (RPl-87) was previously identified as a hand bone based on a comparative analysis of linear measurements. To reassess this anatomical allocation, a morphological investigation of the phalanx was conducted using three-dimensional geometric morphometrics, thereby allowing for a more detailed comparison of shape differences. The results contradict the previous assessment and instead suggest that RPl-87 was likely a foot bone from the second or fifth ray. The comparison with phalanges of extant primates also highlights morphological similarities with the terrestrial primates Gorilla and Papio. This study, therefore, tentatively supports a primarily terrestrial locomotion for O. macedoniensis, agreeing with evidence from other disciplines. The second and third studies aim to reconstruct habitual manual activity in early hominins. Study II combines the multivariate analysis of muscle attachment site (entheseal) patterns of the first metacarpal with a multivariate analysis of overall bone shape, thereby addressing habitual activity and mechanical efficiency within the same framework. We investigated a comparative sample of later Homo, including Homo sapiens and Homo neanderthalensis, and different recent great ape species. The early fossil hominin sample includes Homo naledi, Australopithecus sediba, Australopithecus afarensis, Australopithecus africanus, and SK84, an early hominin from Swartkrans with disputed species attribution. According to the results, later Homo and great apes differ clearly in their attachment site proportions of the first dorsal interosseus, a muscle heavily involved in tool-related behaviors. All early hominins, except for A. africanus, present entheseal patterns characterized by a relatively large attachment site of this muscle, supporting human-like hand use and, potentially, tool use in these species. Importantly, A. sediba and A. afarensis combine human-like entheseal patterns with an ape-like morphology of the first metacarpal. This study highlights that, despite their limited manual dexterity (as shown by metacarpal shape), some hominins as early as A. afarensis habitually used their thumb similarly to humans and potentially engaged in tool-related behaviors. Consequently, our results suggest that biomechanical adaptations for increased manual dexterity on the hand skeleton occurred long after the emergence of human- like hand use. The third study builds upon these results and expands the analysis of entheseal patterns to more hand muscles, focusing on the Australopithecus sample. The analysis shows that later Homo and the extant great apes differ in entheseal patterns. Like in Study II, the later Homo group shows a proportionally large attachment site of the first dorsal interosseus. Additionally, individuals of this group are characterized by large attachment sites on the fifth finger. The muscles in this pattern are involved in behaviors that play important roles in everyday human-like hand use, such as power grasping, in-hand stabilization and manipulation of objects. Among the australopiths, A. sediba and A. afarensis show similar, although not identical, attachment site proportions to later Homo. Our results thereby support a human-like hand use in these species that heavily relies on the muscles on the margins of the hand and, notably, the fifth finger. The fifth ray of A. afarensis, in particular, had previously been assessed as too inefficient and limited in movement to allow for the production of Lomekwian stone tools. These contradicting results once again highlight the need to differentiate between bone morphology that is behaviorally plastic and morphology that represents biomechanical adaptations. In contrast to the other australopiths, the entheseal pattern of A. africanus is unlike both that of later Homo and the extant great apes, suggesting that it engaged in a unique range of manual activities. In summary, this study produces evidence for human-like hand use in some Australopithecus specimens and emphasizes the value of activity reconstruction for human-evolutionary studies. Altogether, this dissertation uses virtual methods to investigate hand (and foot) bone morphology to address manual and locomotor behaviors in the hominid and hominin fossil records. It also adapts these methods to allow a meaningful examination of isolated bones frequently occurring in the fossil record
Facetten der Osteologie
No full textBones represent a fascinating medium that has accompanied mankind in many forms since time immemorial, be it as a raw material, as an object of religious worship or as an object in art and culture. However, less attention is paid to the fact that bones contain a great deal of information about their owners and the circumstances of their lives that can be preserved long after death. The subject of osteology, with its diverse and interdisciplinary subject areas, is dedicated to the task of unlocking this information and giving shape to the beings behind the bones. As an anthropologist at the State Office for the Preservation of Monuments and as a professor at the Eberhard Karls University of Tübingen, Prof. Dr. Joachim Wahl has dedicated his life to osteology and its many facets. This volume has been compiled in his honor and to pay tribute to his work. In a total of 13 articles, renowned experts from the fields of anthropology, archaeozoology and forensics deal with the subject of bones and take the reader on a fascinating journey from the beginnings of the Neolithic Age in Europe to the present day
- …
