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Juan Luis Arsuaga - One of the best experts on this subject based on the ideXlab platform.

  • Diachronic analysis of cultural dental wear at the Atapuerca sites (Spain)
    Quaternary International, 2017
    Co-Authors: Marina Lozano, Juan Luis Arsuaga, J.m. Bermúdez De Castro, E. Carbonell
    Abstract:

    Abstract Cultural dental wear provides useful information about the use of anterior teeth for non-masticatory purposes. Non-alimentary tasks are usually related to economic and cultural activities. The presence of cultural dental wear has been checked in four different Homo Species from the Sierra de Atapuerca sites (Sima del Elefante, Gran Dolina-TD6, Sima de los Huesos and El Mirador cave). The chronology of these sites ranges from more than one million to 4000 years ago. Evidence of dental wear has been documented in the four Homo Species analysed, confirming that hominins began using their teeth as tools as far back as one million years ago. Each Species exhibits specific typologies and frequencies of dental wear features. Also, dental features are located on different dental surfaces and tooth types, indicating a diversity of activities carried out using the anterior teeth as a tool. The use of the teeth as a tool was a widespread habit in the genus Homo . However, the diversity of dental wear patterns can be related to cultural and economic activities, broadening our knowledge of the behaviour of ancient hominins.

  • A geometric morphometric analysis of hominin lower molars: Evolutionary implications and overview of postcanine dental variation.
    Journal of human evolution, 2015
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón, Juan Luis Arsuaga
    Abstract:

    Lower molars have been extensively studied in the context of hominin evolution using classic and geometric morphometric analyses, 2D and 3D approaches, evaluations of the external (outer enamel surface) and internal anatomy (dentine, pulp chamber, and radicular canals), and studies of the crown and root variation. In this study, we present a 2D geometric morphometric analysis of the crown anatomy of lower first, second, and third molars of a broad sample of hominins, including Pliocene and Lower, Middle, and Upper Pleistocene Species coming from Africa, Asia, and Europe. We show that shape variability increases from first to second and third molars. While first molars tend to retain a relatively stable 5-cusped conformation throughout the hominin fossil record, second and third molars show marked distal reductions in later Homo Species. This trend to distal reduction is similar to that observed in previous studies of premolars and upper second and third molars, and points to a correlated reduction of distal areas across the whole postcanine dentition. Results on lower molar variation, as well as on other postcanine teeth, show certain trends in European Pleistocene populations from the Atapuerca sites. Middle Pleistocene hominins from Sima de los Huesos show Neanderthal affinities and strong dental reduction, especially in the most distal molars. The degree of dental reduction in this population is stronger than that observed in classic Neanderthals. Homo antecessor hominins from Gran Dolina-TD6 have primitive lower teeth that contrast with their more derived upper teeth. The evolutionary implications of these dental affinities are discussed in light of recent paleogenetic studies.

  • A geometric morphometric analysis of hominin upper premolars. Shape variation and morphological integration
    Journal of human evolution, 2011
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón, Juan Luis Arsuaga
    Abstract:

    This paper continues the series of articles initiated in 2006 that analyse hominin dental crown morphology by means of geometric morphometric techniques. The detailed study of both upper premolar occlusal morphologies in a comprehensive sample of hominin fossils, including those coming from the Gran Dolina-TD6 and Sima de los Huesos sites from Atapuerca, Spain, complement previous works on lower first and second premolars and upper first molars. A morphological gradient consisting of the change from asymmetric to symmetric upper premolars and a marked reduction of the lingual cusp in recent Homo Species has been observed in both premolars. Although percentages of correct classification based on upper premolar morphologies are not very high, significant morphological differences between Neanderthals (and European middle Pleistocene fossils) and modern humans have been identified, especially in upper second premolars. The study of morphological integration between premolar morphologies reveals significant correlations that are weaker between upper premolars than between lower ones and significant correlations between antagonists. These results have important implications for understanding the genetic and functional factors underlying dental phenotypic variation and covariation.

  • 1997-2001: el estatus de Homo antecessor
    2009
    Co-Authors: José María Bermúdez De Castro, Juan Luis Arsuaga
    Abstract:

    RESUMEN: En 1997 denominamos una nueva especie del genero Homo, H. antecessor (Bermudez de Castro et alii, 1997), para incluir la variabilidad observada en los restos humanos fosiles procedentes del nivel TD6 (Estrato Autota) del yacimiento de la Gtan Dolina de la Sierra de Atapuerca (Burgos). Los nuevos hallazgos realizados desde entonces en otros yacimientos europeos (e. g. Dmanisi, Republica de Georgia), asi como la reinterpretacion de algunos ejemplares fosiles han reforzado la credibilidad de la especie. El hipodigma de H. antecessor se ha incrementado con la inclusion del especimen descubierto en 1994 cerca de la localidad italiana de Ceprano. Por otra parte, la especie H. antecessor continua siendo la mejot candidata para representar el ultimo antecesor comun de los neandertales y de las poblaciones modernas. ABSTRACT: In 1997 we named a new Homo Species, H. antecessor (Bermudez de Castro et alii, 1997), to accommodate the variability observed in the human fossil remains coming from the TD6 level (Aurora Stratum) of the Gran Dolina site in the Sierra de Atapuerca (Burgos, Spain). The new findings made since then in other European sites (e. g. Dmanisi, Republic of Georgia), as well as the re-examination of some fossil specimens have strengthened the credit of the Species. The H. antecessor hypodigm has increased with the inclusion of the adult calvaria discovered in 1994 near Ceprano (Italy). Moteover, H. antecessor is still the best candidate for representing the last common ancestor to Neanderthals and modem humans.

  • Hominin lower second premolar morphology: evolutionary inferences through geometric morphometric analysis.
    Journal of human evolution, 2006
    Co-Authors: María Martinón-torres, J.m. Bermúdez De Castro, Markus Bastir, Alejandro Gómez, Susana Sarmiento, A. Muela, Juan Luis Arsuaga
    Abstract:

    Mandibular premolars are increasingly used in taxon-specific diagnostic analyses of hominins. Among the principal difficulties in these evaluations is the absence of discrete, discernible, and comparable anatomical structures for rigorous quantitative assessment. Previous research has addressed either internal crown surface features (such as cusps and fossae) or the morphology of the crown outline. In the present paper, we integrate both types of information in the examination of morphological variation of lower P4s (n = 96) among various fossil hominin Species with an emphasis on genus Homo. We use a set of 34 2D landmarks combining coordinate data from four classical dental landmarks on the occlusal surface and 30 sliding semilandmarks of the crown outline. Our results indicate that external shape variation is closely related to the configuration of the occlusal morphological features and influenced by dental size. The external and internal shapes of P4 are polymorphic but still useful in depicting a primitive-derived gradient. The primitive pattern seems to have been an asymmetrical contour with a mesially displaced metaconid, development of a bulging talonid, and a broad occlusal polygon. The trend toward dental reduction during the Pleistocene produced different morphological variants with a reduced occlusal polygon and decreased lingual occlusal surface in later Homo Species. Homo heidelbergensis/neanderthalensis have fixed plesiomorphic traits in high percentages, whereas in modern humans a symmetrical outline with a centered metaconid and talonid reduction evolved.

Aida Gómez-robles - One of the best experts on this subject based on the ideXlab platform.

  • Brain enlargement and dental reduction were not linked in hominin evolution
    Proceedings of the National Academy of Sciences of the United States of America, 2017
    Co-Authors: Aida Gómez-robles, Jeroen B. Smaers, Ralph L. Holloway, P. David Polly, Bernard Wood
    Abstract:

    The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin Species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo Species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans.

  • A geometric morphometric analysis of hominin lower molars: Evolutionary implications and overview of postcanine dental variation.
    Journal of human evolution, 2015
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón, Juan Luis Arsuaga
    Abstract:

    Lower molars have been extensively studied in the context of hominin evolution using classic and geometric morphometric analyses, 2D and 3D approaches, evaluations of the external (outer enamel surface) and internal anatomy (dentine, pulp chamber, and radicular canals), and studies of the crown and root variation. In this study, we present a 2D geometric morphometric analysis of the crown anatomy of lower first, second, and third molars of a broad sample of hominins, including Pliocene and Lower, Middle, and Upper Pleistocene Species coming from Africa, Asia, and Europe. We show that shape variability increases from first to second and third molars. While first molars tend to retain a relatively stable 5-cusped conformation throughout the hominin fossil record, second and third molars show marked distal reductions in later Homo Species. This trend to distal reduction is similar to that observed in previous studies of premolars and upper second and third molars, and points to a correlated reduction of distal areas across the whole postcanine dentition. Results on lower molar variation, as well as on other postcanine teeth, show certain trends in European Pleistocene populations from the Atapuerca sites. Middle Pleistocene hominins from Sima de los Huesos show Neanderthal affinities and strong dental reduction, especially in the most distal molars. The degree of dental reduction in this population is stronger than that observed in classic Neanderthals. Homo antecessor hominins from Gran Dolina-TD6 have primitive lower teeth that contrast with their more derived upper teeth. The evolutionary implications of these dental affinities are discussed in light of recent paleogenetic studies.

  • A geometric morphometric analysis of hominin upper premolars. Shape variation and morphological integration
    Journal of human evolution, 2011
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón, Juan Luis Arsuaga
    Abstract:

    This paper continues the series of articles initiated in 2006 that analyse hominin dental crown morphology by means of geometric morphometric techniques. The detailed study of both upper premolar occlusal morphologies in a comprehensive sample of hominin fossils, including those coming from the Gran Dolina-TD6 and Sima de los Huesos sites from Atapuerca, Spain, complement previous works on lower first and second premolars and upper first molars. A morphological gradient consisting of the change from asymmetric to symmetric upper premolars and a marked reduction of the lingual cusp in recent Homo Species has been observed in both premolars. Although percentages of correct classification based on upper premolar morphologies are not very high, significant morphological differences between Neanderthals (and European middle Pleistocene fossils) and modern humans have been identified, especially in upper second premolars. The study of morphological integration between premolar morphologies reveals significant correlations that are weaker between upper premolars than between lower ones and significant correlations between antagonists. These results have important implications for understanding the genetic and functional factors underlying dental phenotypic variation and covariation.

  • EVOLUTIONARY NOVELTIES AND LOSSES IN GEOMETRIC MORPHOMETRICS: A PRACTICAL APPROACH THROUGH HOMININ MOLAR MORPHOLOGY
    Evolution; international journal of organic evolution, 2011
    Co-Authors: Aida Gómez-robles, María Martinón-torres, Leyre Prado-simón, Anthony J. Olejniczak, José María Bermúdez De Castro
    Abstract:

    Geometric morphometric techniques may offer a promising methodological approach to analyze evolutionary novelties in a quantitative framework. Nevertheless, and despite continuous improvements to this methodology, the inclusion of novel features in these studies presents some difficulties. In the present study, different methods to explicitly include novel traits in geometric morphometric analyses are compared, including Homology-free approaches, landmark-based approaches, and combinations of both techniques. The two-dimensional occlusal morphology of the lower second molar in multiple hominin Species was chosen to evaluate these methods, as an example of an anatomical structure including one novelty: a distal fifth cusp is present in earlier hominins, and notably absent in many later Homo Species. Results reveal that different approaches provide different results, highlighting that the design of the conformations of landmarks has a high impact on the inferred conclusions. Among diverse methods, a combined approach including landmarks, sliding semilandmarks, and only one landmark related to the studied novelty (an indicator of its absence or presence and of its size, when present), was able to directly discern structures with and without the novel feature, circumventing some of the methodological difficulties associated with these traits. This study demonstrates the ability of geometric morphometric techniques to investigate evolutionary novelties and explores the implications of different methods, providing a reference context for future studies.

  • Crown size and cusp proportions in Homo antecessor upper first molars. A comment on Quam et al. 2009.
    Journal of anatomy, 2010
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón
    Abstract:

    A recent evaluation of upper first molar (M1) crown size and cusp proportions in the genus Homo (Quam et al. 2009) describes Homo antecessor as maintaining a primitive pattern of cusp proportions, similar to that identified in australopithecines and the earliest members of the genus Homo. These results contrast with those of Gomez-Robles et al. (2007), who described the crown shape in these molars as derived and similar to Neanderthals and European Homo heidelbergensis. The reassessment of these measurements following the same methodology described by Quam et al. (2009) in all the M1s that are currently part of the hypodigm of H. antecessor demonstrates that the fossils from TD6 not only have the same cusp proportions identified in later Homo Species, but also a strongly reduced metacone and a large hypocone shared with Middle and Upper Pleistocene members of the Neanderthal lineage. The evolutionary significance of these features should be evaluated in light of the results provided by recently discovered dental, cranial, mandibular, and postcranial H. antecessor fossils.

Lucas K. Delezene - One of the best experts on this subject based on the ideXlab platform.

  • Distinct mandibular premolar crown morphology in Homo naledi and its implications for the evolution of Homo Species in southern Africa.
    Scientific reports, 2020
    Co-Authors: Thomas W. Davies, Lucas K. Delezene, Lee R. Berger, Philipp Gunz, Jean-jacques Hublin, Agness Gidna, Matthew M. Skinner
    Abstract:

    Homo naledi displays a combination of features across the skeleton not found in any other hominin taxon, which has hindered attempts to determine its placement within the hominin clade. Using geometric morphometrics, we assess the morphology of the mandibular premolars of the Species at the enamel-dentine junction (EDJ). Comparing with specimens of Paranthropus, Australopithecus and Homo (n = 97), we find that the H. naledi premolars from the Dinaledi chamber consistently display a suite of traits (e.g., tall crown, well-developed P3 and P4 metaconid, strongly developed P3 mesial marginal ridge, and a P3 > P4 size relationship) that distinguish them from known hominin groups. Premolars from a second locality, the Lesedi Chamber, are consistent with this morphology. We also find that two specimens from South Africa, SK 96 (usually attributed to Paranthropus) and Stw 80 (Homo sp.), show similarities to the Species, and we discuss a potential evolutionary link between H. naledi and hominins from Sterkfontein and Swartkrans.

  • The deciduous dentition of Homo naledi: A comparative study.
    Journal of human evolution, 2019
    Co-Authors: Shara E. Bailey, Juliet K. Brophy, Jacopo Moggi-cecchi, Lucas K. Delezene
    Abstract:

    Abstract In 2013, 2014 new hominin remains were uncovered in the Dinaledi chamber of the Rising Star cave system in South Africa. In 2015 Berger and colleagues identified these remains as belonging to a new Species Homo naledi (Berger et al., 2015). Subsequent comparative studies of the skull, postcrania and permanent dentition have supported this taxonomic affiliation (Harcourt-Smith et al., 2015; Kivell et al., 2015; Irish et al., 2018). The deciduous teeth can offer unique insights into hominin evolution. Due to their early onset and rapid development their morphology is thought to be under stronger genetic control and less influenced by environment than are the permanent teeth. In this study we compared the H. naledi deciduous teeth from the 2013–2014 excavations to samples representing much of the hominin clade including Australopithecus afarensis, Australopithecus africanus, Paranthropus boisei, Paranthropus robustus, early Homo, Homo antecessor, Homo erectus s.l., Homo floresiensis, Middle Pleistocene Homo, Homo neanderthalensis, early Homo sapiens and recent H. sapiens from Sub-Saharan Africa. By making such a broad morphological comparison, we aimed to contextualize the Dinaledi hominins and to further assess the validity of their taxonomic assignment. Our analysis of the deciduous teeth revealed a unique combination of features that mirror (but also expand) that found in the permanent teeth. This mosaic includes an asymmetrical lower canine with a distal tubercle, an upper first molar with a large hypocone and epicrista associated with a mesial cuspule, a molarized lower first molar resembling Paranthropus, and upper and lower second molars that resemble later Homo in their lack of accessory cusps. The unique combination of deciduous dental characters supports previous studies assigning H. naledi to a new Species, although its phylogenetic position vis-a-vis other Homo Species remains ambiguous.

  • Mandibular molar root and pulp cavity morphology in Homo naledi and other Plio-Pleistocene hominins
    Journal of human evolution, 2019
    Co-Authors: Kornelius Kupczik, Lucas K. Delezene, Matthew M. Skinner
    Abstract:

    Abstract The craniomandibular morphology of Homo naledi shows variable resemblances with Species across Homo, which confounds an easy assessment of its phylogenetic position. In terms of skull shape, H. naledi has its closest affinities with Homo erectus, while mandibular shape places it closer to early Homo. From a tooth crown perspective, the smaller molars of H. naledi make it distinct from early Homo and H. erectus. Here, we compare the mandibular molar root morphology of six H. naledi individuals from the Dinaledi Chamber to those of African and Eurasian Plio-Pleistocene fossil hominins (totalling 183 mandibular first, second and third molars). The analysis of five root metric variables (cervical plane area, root length, root cervix volume, root branch volume, and root surface area) derived from microCT reconstructions reveals that the molar roots of H. naledi are smaller than those of Homo habilis, Homo rudolfensis, and H. erectus, but that they resemble those of three Homo sp. specimens from Swartkrans and Koobi Fora in size and overall appearance. Moreover, though H. naledi molar roots are similar in absolute size to Pleistocene Homo sapiens, they differ from H. sapiens in having a larger root volume for a given cervical plane area and less taurodont roots; the root cervix-to-branch proportions of H. naledi are comparable to those of Australopithecus africanus and Species of Paranthropus. H. naledi also shares a metameric root volume pattern (M2 > M3 > M1) with Australopithecus and Paranthropus but not with any of the other Homo Species (M2 > M1 > M3). Our findings therefore concur with previous studies that found that H. naledi shares plesiomorphic features with early Homo, Australopithecus, and Paranthropus. While absolute molar root size aligns H. naledi with Homo from North and South Africa, it is distinguishable from these in terms of root volumetric proportions.

  • Body size, brain size, and sexual dimorphism in Homo naledi from the Dinaledi Chamber.
    Journal of human evolution, 2017
    Co-Authors: Heather M. Garvin, Marina Elliott, Lucas K. Delezene, John Hawks, Steven E. Churchill, Lee R. Berger, Trenton W. Holliday
    Abstract:

    Abstract Homo erectus and later humans have enlarged body sizes, reduced sexual dimorphism, elongated lower limbs, and increased encephalization compared to Australopithecus , together suggesting a distinct ecological pattern. The mosaic expression of such features in early Homo , including Homo habilis , Homo rudolfensis , and some early H. erectus , suggests that these traits do not constitute an integrated package. We examined the evidence for body mass, stature, limb proportions, body size and dental size dimorphism, and absolute and relative brain size in Homo naledi as represented in the Dinaledi Chamber sample. H. naledi stature and body mass are low compared to reported values for H. erectus , with the exception of some of the smaller bodied Dmanisi H. erectus specimens, and overlap with larger Australopithecus and early Homo estimates . H. naledi endocranial volumes (465–560 cc) and estimates of encephalization quotient are also similar to Australopithecus and low compared to all Homo specimens, with the exception of Homo floresiensis (LB1) and the smallest Dmanisi H. erectus specimen (D4500). Unlike Australopithecus , but similar to derived members of genus Homo , the Dinaledi assemblage of H. naledi exhibits both low levels of body mass and dental size variation, with an estimated body mass index of sexual dimorphism less than 20%, and appears to have an elongated lower limb. Thus, the H. naledi bauplan combines features not typically seen in Homo Species (e.g., small brains and bodies) with those characteristic of H. erectus and more recent Homo Species (e.g., reduced mass dimorphism, elongated lower limb).

  • Homo naledi: a new Species of hominin from the Dinaledi Chamber, South Africa
    Paleoanthropology, 2016
    Co-Authors: Darryl J. De Ruiter, Heather M. Garvin, Lucas K. Delezene, John Hawks, Steven E. Churchill, Lee R. Berger, Peter Schmid, Tracy L. Kivell, Scott A. Williams, Jeremy M. Desilva
    Abstract:

    Homo naledi is a previously unknown Species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Gauteng, South Africa. This Species is characterized by body mass and stature similar to small-bodied human populations, with a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo Species including H. erectus, H. habilis, or H. rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike leg and foot. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, fingers, pelvis, and proximal femur. Nonetheless, the shared derived features that connect H. naledi with other members of Homo occupy most regions of the H. naledi skeleton and represent distinct functional systems, including locomotion, manipulation, and mastication. With at least 15 individuals and most skeletal elements represented by multiple specimens, this is the largest assemblage of a single Species of hominins yet discovered in Africa. To date we have recovered more than 1, 700 specimens, with comprehensive representation of skeletal elements across the lifespan, and from multiple individuals. Regardless of the fact that the Dinaledi Chamber is currently undated, H. naledi highlights gaps in our understanding of ancient Homo across the vast geographic span of the African continent. The tree of Homo-like hominins is far from complete: we have missed key transitional forms and lineages that persisted for hundreds of thousands of years.

María Martinón-torres - One of the best experts on this subject based on the ideXlab platform.

  • Virtual reconstruction of the Early Pleistocene mandible ATD6-96 from Gran Dolina-TD6-2 (Sierra De Atapuerca, Spain).
    American journal of physical anthropology, 2015
    Co-Authors: José María Bermúdez De Castro, María Martinón-torres, Laura Martín-francés, Mario Modesto-mata, Marina Martínez De Pinillos, Cecilia García-campos, José Miguel Carretero
    Abstract:

    OBJECTIVES: In this report, we present a further study of the late Early Pleistocene ATD6-96 human mandible, recovered from the TD6-2 level of the Gran Dolina cave site (Sierra de Atapuerca, northern Spain) and attributed to Homo antecessor. METHODS: ATD6-96 consists of a left half of a gracile mandible of an adult individual with the premolars and molars in place that is broken at the level of the lateral incisor-canine septum. The present analysis is based on a virtual reconstruction of the whole mandible by means of computed tomography (CT). We have reconstructed the symphysis using information from a modern human sample, as well as from a wide sample composed of several Homo specimens. RESULTS: This research has allowed us to record new variables with taxonomic and phylogenetic interest. We have estimated the length/width index of the alveolar arcade, as well as the percentage of the arcade length with regard to the total length. The latter confirms that ATD6-96 shares with all African and Asian Homo Species a primitive structural pattern, as it was established in previous studies. In constrast, the length/width index of the alveolar arcade in the H. antecessor specimen is close to the mean values of Neandertals and the Atapuerca-Sima de los Huesos hominins. CONCLUSIONS: H. antecessor is derived regarding the shape of the mandibular alveolar arcade within the genus Homo and points to an early divergence from contemporaneous African populations. Our results also ratify the affinities of H. antecessor with Neanderthals, although the precise relationship with this lineage needs further research.

  • A geometric morphometric analysis of hominin lower molars: Evolutionary implications and overview of postcanine dental variation.
    Journal of human evolution, 2015
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón, Juan Luis Arsuaga
    Abstract:

    Lower molars have been extensively studied in the context of hominin evolution using classic and geometric morphometric analyses, 2D and 3D approaches, evaluations of the external (outer enamel surface) and internal anatomy (dentine, pulp chamber, and radicular canals), and studies of the crown and root variation. In this study, we present a 2D geometric morphometric analysis of the crown anatomy of lower first, second, and third molars of a broad sample of hominins, including Pliocene and Lower, Middle, and Upper Pleistocene Species coming from Africa, Asia, and Europe. We show that shape variability increases from first to second and third molars. While first molars tend to retain a relatively stable 5-cusped conformation throughout the hominin fossil record, second and third molars show marked distal reductions in later Homo Species. This trend to distal reduction is similar to that observed in previous studies of premolars and upper second and third molars, and points to a correlated reduction of distal areas across the whole postcanine dentition. Results on lower molar variation, as well as on other postcanine teeth, show certain trends in European Pleistocene populations from the Atapuerca sites. Middle Pleistocene hominins from Sima de los Huesos show Neanderthal affinities and strong dental reduction, especially in the most distal molars. The degree of dental reduction in this population is stronger than that observed in classic Neanderthals. Homo antecessor hominins from Gran Dolina-TD6 have primitive lower teeth that contrast with their more derived upper teeth. The evolutionary implications of these dental affinities are discussed in light of recent paleogenetic studies.

  • A geometric morphometric analysis of hominin upper premolars. Shape variation and morphological integration
    Journal of human evolution, 2011
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón, Juan Luis Arsuaga
    Abstract:

    This paper continues the series of articles initiated in 2006 that analyse hominin dental crown morphology by means of geometric morphometric techniques. The detailed study of both upper premolar occlusal morphologies in a comprehensive sample of hominin fossils, including those coming from the Gran Dolina-TD6 and Sima de los Huesos sites from Atapuerca, Spain, complement previous works on lower first and second premolars and upper first molars. A morphological gradient consisting of the change from asymmetric to symmetric upper premolars and a marked reduction of the lingual cusp in recent Homo Species has been observed in both premolars. Although percentages of correct classification based on upper premolar morphologies are not very high, significant morphological differences between Neanderthals (and European middle Pleistocene fossils) and modern humans have been identified, especially in upper second premolars. The study of morphological integration between premolar morphologies reveals significant correlations that are weaker between upper premolars than between lower ones and significant correlations between antagonists. These results have important implications for understanding the genetic and functional factors underlying dental phenotypic variation and covariation.

  • EVOLUTIONARY NOVELTIES AND LOSSES IN GEOMETRIC MORPHOMETRICS: A PRACTICAL APPROACH THROUGH HOMININ MOLAR MORPHOLOGY
    Evolution; international journal of organic evolution, 2011
    Co-Authors: Aida Gómez-robles, María Martinón-torres, Leyre Prado-simón, Anthony J. Olejniczak, José María Bermúdez De Castro
    Abstract:

    Geometric morphometric techniques may offer a promising methodological approach to analyze evolutionary novelties in a quantitative framework. Nevertheless, and despite continuous improvements to this methodology, the inclusion of novel features in these studies presents some difficulties. In the present study, different methods to explicitly include novel traits in geometric morphometric analyses are compared, including Homology-free approaches, landmark-based approaches, and combinations of both techniques. The two-dimensional occlusal morphology of the lower second molar in multiple hominin Species was chosen to evaluate these methods, as an example of an anatomical structure including one novelty: a distal fifth cusp is present in earlier hominins, and notably absent in many later Homo Species. Results reveal that different approaches provide different results, highlighting that the design of the conformations of landmarks has a high impact on the inferred conclusions. Among diverse methods, a combined approach including landmarks, sliding semilandmarks, and only one landmark related to the studied novelty (an indicator of its absence or presence and of its size, when present), was able to directly discern structures with and without the novel feature, circumventing some of the methodological difficulties associated with these traits. This study demonstrates the ability of geometric morphometric techniques to investigate evolutionary novelties and explores the implications of different methods, providing a reference context for future studies.

  • Crown size and cusp proportions in Homo antecessor upper first molars. A comment on Quam et al. 2009.
    Journal of anatomy, 2010
    Co-Authors: Aida Gómez-robles, María Martinón-torres, José María Bermúdez De Castro, Leyre Prado-simón
    Abstract:

    A recent evaluation of upper first molar (M1) crown size and cusp proportions in the genus Homo (Quam et al. 2009) describes Homo antecessor as maintaining a primitive pattern of cusp proportions, similar to that identified in australopithecines and the earliest members of the genus Homo. These results contrast with those of Gomez-Robles et al. (2007), who described the crown shape in these molars as derived and similar to Neanderthals and European Homo heidelbergensis. The reassessment of these measurements following the same methodology described by Quam et al. (2009) in all the M1s that are currently part of the hypodigm of H. antecessor demonstrates that the fossils from TD6 not only have the same cusp proportions identified in later Homo Species, but also a strongly reduced metacone and a large hypocone shared with Middle and Upper Pleistocene members of the Neanderthal lineage. The evolutionary significance of these features should be evaluated in light of the results provided by recently discovered dental, cranial, mandibular, and postcranial H. antecessor fossils.

Matthew M. Skinner - One of the best experts on this subject based on the ideXlab platform.

  • Distinct mandibular premolar crown morphology in Homo naledi and its implications for the evolution of Homo Species in southern Africa.
    Scientific reports, 2020
    Co-Authors: Thomas W. Davies, Lucas K. Delezene, Lee R. Berger, Philipp Gunz, Jean-jacques Hublin, Agness Gidna, Matthew M. Skinner
    Abstract:

    Homo naledi displays a combination of features across the skeleton not found in any other hominin taxon, which has hindered attempts to determine its placement within the hominin clade. Using geometric morphometrics, we assess the morphology of the mandibular premolars of the Species at the enamel-dentine junction (EDJ). Comparing with specimens of Paranthropus, Australopithecus and Homo (n = 97), we find that the H. naledi premolars from the Dinaledi chamber consistently display a suite of traits (e.g., tall crown, well-developed P3 and P4 metaconid, strongly developed P3 mesial marginal ridge, and a P3 > P4 size relationship) that distinguish them from known hominin groups. Premolars from a second locality, the Lesedi Chamber, are consistent with this morphology. We also find that two specimens from South Africa, SK 96 (usually attributed to Paranthropus) and Stw 80 (Homo sp.), show similarities to the Species, and we discuss a potential evolutionary link between H. naledi and hominins from Sterkfontein and Swartkrans.

  • Mandibular molar root and pulp cavity morphology in Homo naledi and other Plio-Pleistocene hominins
    Journal of human evolution, 2019
    Co-Authors: Kornelius Kupczik, Lucas K. Delezene, Matthew M. Skinner
    Abstract:

    Abstract The craniomandibular morphology of Homo naledi shows variable resemblances with Species across Homo, which confounds an easy assessment of its phylogenetic position. In terms of skull shape, H. naledi has its closest affinities with Homo erectus, while mandibular shape places it closer to early Homo. From a tooth crown perspective, the smaller molars of H. naledi make it distinct from early Homo and H. erectus. Here, we compare the mandibular molar root morphology of six H. naledi individuals from the Dinaledi Chamber to those of African and Eurasian Plio-Pleistocene fossil hominins (totalling 183 mandibular first, second and third molars). The analysis of five root metric variables (cervical plane area, root length, root cervix volume, root branch volume, and root surface area) derived from microCT reconstructions reveals that the molar roots of H. naledi are smaller than those of Homo habilis, Homo rudolfensis, and H. erectus, but that they resemble those of three Homo sp. specimens from Swartkrans and Koobi Fora in size and overall appearance. Moreover, though H. naledi molar roots are similar in absolute size to Pleistocene Homo sapiens, they differ from H. sapiens in having a larger root volume for a given cervical plane area and less taurodont roots; the root cervix-to-branch proportions of H. naledi are comparable to those of Australopithecus africanus and Species of Paranthropus. H. naledi also shares a metameric root volume pattern (M2 > M3 > M1) with Australopithecus and Paranthropus but not with any of the other Homo Species (M2 > M1 > M3). Our findings therefore concur with previous studies that found that H. naledi shares plesiomorphic features with early Homo, Australopithecus, and Paranthropus. While absolute molar root size aligns H. naledi with Homo from North and South Africa, it is distinguishable from these in terms of root volumetric proportions.

  • Associated ilium and femur from Koobi Fora, Kenya, and postcranial diversity in early Homo
    Journal of human evolution, 2015
    Co-Authors: Carol V. Ward, Matthew M. Skinner, Ashley S. Hammond, Craig S. Feibel, Louise N. Leakey, Elizabeth A. Moffett, J. Michael Plavcan, Fred Spoor, Meave G. Leakey
    Abstract:

    During the evolution of hominins, it is generally accepted that there was a shift in postcranial morphology between Australopithecus and the genus Homo. Given the scarcity of associated remains of early Homo, however, relatively little is known about early Homo postcranial morphology. There are hints of postcranial diversity among Species, but our knowledge of the nature and extent of potential differences is limited. Here we present a new associated partial ilium and femur from Koobi Fora, Kenya, dating to 1.9 Ma (millions of years ago) that is clearly attributable to the genus Homo but documents a pattern of morphology not seen in eastern African early Homo erectus. The ilium and proximal femur share distinctive anatomy found only in Homo. However, the geometry of the femoral midshaft and contour of the pelvic inlet do not resemble that of any specimens attributed to H. erectus from eastern Africa. This new fossil confirms the presence of at least two postcranial morphotypes within early Homo, and documents diversity in postcranial morphology among early Homo Species that may reflect underlying body form and/or adaptive differences.

  • Variation in enamel thickness within the genus Homo.
    Journal of human evolution, 2012
    Co-Authors: Tanya M. Smith, Matthew M. Skinner, Paul Tafforeau, John P. Zermeno, Anthony J. Olejniczak, Jakov Radovčić, Almut Hoffmann, Michel Toussaint, Robert Kruszynski, Colin G. Menter
    Abstract:

    Recent humans and their fossil relatives are classified as having thick molar enamel, one of very few dental traits that distinguish hominins from living African apes. However, little is known about enamel thickness in the earliest members of the genus Homo, and recent studies of later Homo report considerable intra- and inter-specific variation. In order to assess taxonomic, geographic, and temporal trends in enamel thickness, we applied micro-computed tomographic imaging to 150 fossil Homo teeth spanning two million years. Early Homo postcanine teeth from Africa and Asia show highly variable average and relative enamel thickness (AET and RET) values. Three molars from South Africa exceed Homo AET and RET ranges, resembling the hyper thick Paranthropus condition. Most later Homo groups (archaic European and north African Homo, and fossil and recent Homo sapiens) possess absolutely and relatively thick enamel across the entire dentition. In contrast, Neanderthals show relatively thin enamel in their incisors, canines, premolars, and molars, although incisor AET values are similar to H. sapiens. Comparisons of recent and fossil H. sapiens reveal that dental size reduction has led to a disproportionate decrease in coronal dentine compared with enamel (although both are reduced), leading to relatively thicker enamel in recent humans. General characterizations of hominins as having 'thick enamel' thus oversimplify a surprisingly variable craniodental trait with limited taxonomic utility within a genus. Moreover, estimates of dental attrition rates employed in paleodemographic reconstruction may be biased when this variation is not considered. Additional research is necessary to reconstruct hominin dietary ecology since thick enamel is not a prerequisite for hard-object feeding, and it is present in most later Homo Species despite advances in technology and food processing.