Nuevo enfoque morfométrico para el estudio de la biomecánica y adaptación de los homininos del Plio-Pleistoceno

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Geografía e Historia, leída el 06-10-2021En la presente tesis doctoral titulada “Nuevo enfoque morfométrico para el estudio dela biomecánica y adaptación de los homininos del Plio-Pleistoceno” se presenta una nueva metodología para el análisis de los huesos largos de grandes simios a partir del uso de modelos tridimensionales, haciendo especial hincapié en la interpretación biomecánica de los restos fósiles relativos a especies de nuestra familia evolutiva. Los recientes hallazgos de nuevas especies fósiles humanas han puesto de manifiesto la gran complejidad de nuestra historia evolutiva y las dificultades que entraña su interpretación. Añadido a esto, el estudio de los huesos largos (húmero, radio, cúbito, fémur, tibia y fíbula) de especies homininas anteriores a la nuestra resulta especialmente problemático por una serie de razones entre las que destaca la obtención de información a partir de restos de pequeño tamaño que, en ocasiones, aparecen muy fragmentados en los yacimientos. Asimismo, existen otro tipo de limitaciones que afectan al estudio de la morfología y biomecánica de los huesos largos, entre las que se encuentran la baja integridad del registro fósil y la escasez de restos postcraneales, la dificultad para delimitar los factores que influyen en la morfología de los huesos y que, por lo tanto, pueden mermar la estimación del vínculo existente entre morfología y función, y el uso de muestras comparativas que incluyen un número muy limitado de grupos y morfologías. Esta tesis doctoral tiene como objetivo principal el desarrollo de un nuevo enfoque morfométrico para el estudio de la biomecánica y adaptación de los homininos del Plio-Pleistoceno apoyado en una caracterización muy detallada de la morfologíaexterna de los huesos largos y la implementación de modelos de clasificación de alta precisión...In the present doctoral thesis entitled "A new morphometric approach to the study of Plio-Pleistocene hominin biomechanics and adaptation" a new 3D methodology for the analysis of great ape long bones with special emphasis on the biomechanical interpretation of human fossil remains is introduced. Recent findings of human fossil specimens and taxa have revealed the great complexity of our evolutionary history and the difficulties involved in its comprehension and interpretation. Moreover, the study of hominin long bone remains (humerus, radius, ulna, femur, tibia, fibula) in Palaeoanthropologyis particularly problematic due to the difficulties involved in the analysis of fragmentary skeletal elements that in many occasions are merely represented by small diaphyseal portions. On top of that, there are several additional limitations that affect our ability to study fossil long bone morphology and draw biomechanical inferences, such as the scarcity and poor integrity of the fossil record; the delimitation of the factors that influence morphology and that might diminish the link between bone morphologyand function; and the widespread use of limited modern reference samples that encompass low degrees of interspecific variability. The main objective of the present research is the development of a new morphometric approach to the study of Plio-Pleistocene hominin biomechanics and adaptation that relies on the detailed quantitative characterisation of the external long bone morphology and the implementation of powerful classification methods...Fac. de Geografía e HistoriaTRUEunpu

Testing accuracy in 2D and 3D geometric morphometric methods for cut mark identification and classification

The analysis of bone surface modifications (BSMs) is a prominent part of paleoanthropological studies, namely taphonomic research. Behavioral interpretations of the fossil record hinge strongly upon correct assessment of BSMs. With the significant impact of microscopic analysis to the study of BSMs, multiple authors have discussed the reliability of these technological improvements for gaining resolution in BSM discrimination. While a certain optimism is present, some important questions are ignored and others overemphasized without appropriate empirical support. This specifically affects the study of cut marks. A diversity of geometric morphometric approaches applied to the study of cut marks have resulted in the coexistence (and competition) of different 2D and 3D methods. The present work builds upon the foundation of experiments presented by Maté-González et al. (2015), Courtenay et al. (2017) and Otárola-Castillo et al. (2018) to contrast for the first time 2D and 3D methods in their resolution of cut mark interpretation and classification. The results presented here show that both approaches are equally valid and that the use of sophisticated 3D methods do not contribute to an improvement in accuracy

A Novel Approach for the Shape Characterisation of Non-Melanoma Skin Lesions Using Elliptic Fourier Analyses and Clinical Images

[EN] The early detection of Non-Melanoma Skin Cancer (NMSC) is crucial to achieve the best treatment outcomes. Shape is considered one of the main parameters taken for the detection of some types of skin cancer such as melanoma. For NMSC, the importance of shape as a visual detection parameter is not well-studied. A dataset of 993 standard camera images containing different types of NMSC and benign skin lesions was analysed. For each image, the lesion boundaries were extracted. After an alignment and scaling, Elliptic Fourier Analysis (EFA) coefficients were calculated for the boundary of each lesion. The asymmetry of lesions was also calculated. Then, multivariate statistics were employed for dimensionality reduction and finally computational learning classification was employed to evaluate the separability of the classes. The separation between malignant and benign samples was successful in most cases. The best-performing approach was the combination of EFA coefficients and asymmetry. The combination of EFA and asymmetry resulted in a balanced accuracy of 0.786 and an Area Under Curve of 0.735. The combination of EFA and asymmetry for lesion classification resulted in notable success rates when distinguishing between benign and malignant lesions. In light of these results, skin lesions’ shape should be integrated as a fundamental part of future detection techniques in clinical screening.SIJunta de Castilla y Leó

An Evaluation of Landmark-Based Methods to Explore Tooth Score Morphology: A Case Study on Felids and Hyenids

Taphonomic studies aim to identify the modifying agents that intervene in bone assemblages found at archaeopaleontological sites. Carnivores may modify, accumulate, or scavenge skeletal parts inflicting tooth marks, including scores, on the cortical surface. Several works have studied tooth score morphology to discern which carnivore group modified the bone assemblages, achieving different results. In the present study, different methods based on the use of landmarks and semilandmarks have been tested to describe and analyze the score profile cross-sections of spotted and brown hyenas, leopards, and lions. According to our results, the already published seven-landmark method is useful in order to differentiate between carnivore species from different families (e.g., felids and hyenids). Meanwhile, felid species (e.g., leopards and lions) cannot be consistently distinguished using any of the methods tested here. In contrast, hyenid species can be morphologically differentiated. On the other hand, the use of semilandmarks does not generally improve morphological characterization and distinction, but low numbers of landmarks and the inclusion of the score’s deepest point might provide the best results when semi-automatic semilandmark models are preferred to avoid sampling biases.The grant IJC2020-043576-I funded by MCIN/AEI/10.13039/501100011033 and the “European Union NextGenerationEU/PRTR” has been awarded to M.C.A. The grant RYC2021-034813-I funded by MCIN/AEI/10.13039/501100011033 and the European Union “NextGenerationEU”/PRTR has been awarded to M.Á.M.-G. During the development of the present work, J.A. was funded by the Euskal Herriko Unibertsitatea [ESPDOC21/05]. L.A.C. is funded by the Spanish Ministry of Science, Innovation and Universities by an FPI Predoctoral grant PRE2019-089411 associated with project RTI2018-099850-B-I0

New taphonomic advances in 3D digital microscopy: A morphological characterisation of trampling marks

The concept of equifinality has become one of the greatest difficulties in the field of taphonomy However, new advances in technology have diminished the margins of error in the interpretation of archaeological sites. The use of multivariate statistics and the most recent advances in microscopic analysis of Bone Surface Modifications (BSMs) have enable a less subjective interpretation of site formation processes. Nevertheless, this broader range of methodological approaches also presents some problems. The capacity of laser scanners in processing inconspicuous and superficial cortical alterations, such as trampling marks, has proven to be problematic. This study presents a new advance towards resolving this problem through the use of the HIROX KH-8700 Digital Microscope, whereby detailed digital three-dimensional (3D) reconstructions are able to pick up such minute BSMs. Through the statistical comparison of the David Laser scanner and the HIROX KH-8700 Digital Microscope, this paper contributes to our understanding of said equipment, followed by a significant advance in the characterisation of superficial BSMs. The combination of advanced microscopy and the application of geometric morphometrics highlights a morphological differentiation between two different types of trampling marks, hereby named scratch and graze trampling marks

A geometric-morphometric assessment of three-dimensional models of experimental cut-marks using flint and quartzite flakes and handaxes

Developments in methodological approaches to high-resolution morphometrical study of cut-mark morphology further our understanding of butchering activities. Identification of micro-morphological variability between different taphonomical alterations on ancient bone allows detection and comparison of bone-surface modifications and associated taphonomical agents and activities. By taking a geometrical-morphometrical approach, data from 3-D laser-scanning and micro-photogrammetrical models of experimental cut-marks enable statistical analysis to classify and distinguish between cut-marks by bifaces from those by flakes, and, in each case, between marks made by flint from those made by quartzite tools. Analysis of two tool types, each made from two raw materials as independent variables, is a methodological advance in morphometrical studies of experimental cutmarks, which hitherto have tended to focus on the respective parts played by tool types or types of raw material in morphometrical characterization of experimental and archaeological cut-marks

Discerning carnivore agency through the three-dimensional study of tooth pits: Revisiting crocodile feeding behaviour at FLK- Zinj and FLK NN3 (Olduvai Gorge, Tanzania)

Hominins and carnivores have shared similar habitats in Africa, evolving as direct competitors for the same prey and spaces. The overlap of their ecological niches has raised an important debate on the role that carnivores played in archaeological site formation. Different analytical techniques differentiate the action of carnivores and humans and identify the type of carnivore involved of which tooth mark analyses are prominent. However, available taphonomic studies present some limitations given the great overlap among tooth mark sizes from different carnivores, enabling only the distinction of size groups, not specific carnivores. In this work, we use a new technique combining three-dimensional (3D) reconstruction and geometric morphometrics (GMM) of tooth pits on equid and bovid bone created by different carnivores (including crocodiles, hyenas, jaguars, lions and wolves) in controlled settings. The 3D methodology we present isolates and differentiates tooth marks generated by different carnivores. We also test the applicability of the technique to ascribe tooth pits recorded on some hominin specimens from FLK Zinj and FLKNN 3 (Bed I, Olduvai Gorge). The tooth marks on the Olduvai OH8 and OH35 hominin fossils, previously assigned to crocodiles show that while OH8 tooth pit morphology falls in the range created by crocodiles, the pits on OH35 can not be interpreted as crocodile-inflicted marks

Spilled ink blots the mind: A reply to Merrit et al. (2018) on subjectivity and bone surface modifications

Categorical variables identifying microscopic features of cut marks produce high accuracy in discrimination of bone surface modifications, but are vulnerable to variable degrees of inter-analyst subjectivity. Metric analyses of cut mark width and depth are presented by Merritt et al. (2018) as a more objective method of identifying cut marks. However, this uni(bi)variate method has shown very high rates of mark classification error when structurally similar marks are compared. Furthermore, within-sample comparison carried out via subsampling shows that different datasets of metric values, obtained with the same type of tool and raw material, are subject to such a high degree of variability that significant differences of homogeneous subsamples are repeatedly obtained, thus preventing any useful analogs to be made. Additionally, this much higher stochastic variability depends on limited knowledge of the contextual processes that intervene in cut mark metric properties, as well as on a mismatch between theoretical premises on the immanent-configurational process-trace dynamics and their confusion during experimental praxis. The selection of specific contextual variables and disregard of others, in addition to the combination of different tool types and raw materials, distorts the resulting cut mark properties. This indicates that even when attempting to use exclusively metric numeric variables, subjectivity is a conditioning factor in analyzing and interpreting cut marks

Geometric Morphometrics and Machine Learning Models Applied to the Study of Late Iron Age Cut Marks from Central Spain

Recently the incorporation of artificial intelligence has allowed the development of valuable methodological advances in taphonomy. Some studies have achieved great precision in identifying the carnivore that produced tooth marks. Additionally, other works focused on human activity have managed to specify what type of tool or raw material was used in the filleting processes identified at the sites. Through the use of geometric morphometrics and machine learning techniques, the present study intends to analyze the cut marks of the Ulaca oppidum (Solosancho, Ávila, Spain) in order to identify the type of tools used during carcass modification. Although the Ulaca oppidum is an Iron Age site, the results suggest that most of the cut marks were produced with flint tools.During the development of the present work J.A. was funded by the Euskal Herriko Unibertsitatea [ESPDOC21/05]. This work has been partially funded by the Ministerio de Ciencia e Innovación (project PID2021-123721OB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER, UE) and Fundación Española para la Ciencia y la Tecnología (FCT-21-17318). M.Á.M.-G. and C.S.B. acknowledges the grant RYC2021-034813-I and RYC2021-034720-I respectively, funded by MCIN/AEI/10.13039/501100011033 and by European Union “NextGenerationEU”/PRTR