Article

Geometric Morphometric Analysis of the Crown Morphology of the Lower First Premolar in Hominins, with Special Attention to Pleistocene Homo

Centro Nacional de Investigación sobre Evolución Humana, Avda. de la Paz, 28, 09006, Burgos, Spain.
Journal of Human Evolution (Impact Factor: 3.73). 10/2008; 55(4):627-38. DOI: 10.1016/j.jhevol.2008.03.011
Source: PubMed

ABSTRACT

This article is the third of a series that explores hominin dental crown morphology by means of geometric morphometrics. After the analysis of the lower second premolar and the upper first molar crown shapes, we apply the same technique to lower first premolar morphology. Our results show a clear distinction between the morphology seen in earlier hominin taxa such as Australopithecus and African early Homo, as well as Asian H. erectus, and more recent groups such as European H. heidelbergensis, H. neanderthalensis, and H. sapiens. The morphology of the earlier hominins includes an asymmetrical outline, a conspicuous talonid, and an occlusal polygon that tends to be large. The morphology of the recent hominins includes a symmetrical outline and a reduced or absent talonid. Within this later group, premolars belonging to H. heidelbergensis and H. neanderthalensis tend to possess a small and mesiolingually-displaced occlusal polygon, whereas H. sapiens specimens usually present expanded and centered occlusal polygons in an almost circular outline. The morphological differences among Paranthropus, Australopithecus, and African early Homo as studied here are small and evolutionarily less significant compared to the differences between the earlier and later homin taxa. In contrast to the lower second premolar and the upper first molar crown, the inclusion of a larger hominin sample of lower first premolars reveals a large allometric component.

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Available from: María Martinón-Torres
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    • "2.2.3. Geometric morphometric (GM) analysis A Cannon EOS 5D digital camera equipped with a 100 mm lens was used to take a high resolution photo of each tooth with the plane formed by its cemento-enamel junction (CEJ) parallel to the camera lens (Martin G omez-Robles et al., 2007 G omez-Robles et al., , 2008 G omez-Robles et al., , 2011). When both antimeres were present and equally well preserved in the comparative sample, only the same side as that represented at the Yiyuan site was chosen. "
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    • "The buccal surface of upper premolars show also a vestigium of a cingulum and several longitudinal grooves that resemble that of other Early and Middle Pleistocene fossils from Asia (except for Panxian Dadong, see Liu et al., 2013 ) and Africa but not from Europe (Martin Xing et al., 2014 Xing et al., , 2015). Both the crown and root of the P 3 are remarkably primitive (Bermúdez de G omez-Robles et al., 2008 ) and different from the European Middle Pleistocene hominins, Neandertals and H. sapiens. Although the H. antecessor P 4 s (ATD6-4 and ATD6-96) exhibit a primitive morphology, with an elongated, subrectangular outline and a mesially displaced metaconid, they also show a reduced occlusal polygon. "
    [Show abstract] [Hide abstract] ABSTRACT: It is eighteen years since the human fossils recovered from the TD6 level of the Gran Dolina cave site, in Sierra de Atapuerca (Burgos, northern Spain) were assigned to a new hominin species, Homo antecessor. This review summarizes the main results obtained from the study of these fossils during this period. The increase of the African and Eurasian fossil record, as well as the application of new methodological approaches, has led to competing interpretations about its hypothetical phylogenetic position and possible evolutionary scenarios. At present, we can argue that this species is defined by a unique mosaic of primitive traits for the Homo clade, a certain number of derived features present in modern humans, a significant suite of derived features shared with Neandertals and their ancestors in the European Middle Pleistocene (in particular with the Atapuerca-Sima de los Huesos hominins), and some derived features shared with the Chinese Middle Pleistocene hominins. From this evidence, we suggest that a speciation event could have occurred in Africa/Western Eurasia, originating a new Homo clade. Homo antecessor, most probably dated to the MIS 21, could be a side branch of this clade placed at the westernmost region of the Eurasian continent.
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    • "We have previously evaluated lower second molar morphology in the context of methodological approaches useful to deal with evolutionary novelties and losses (G Robles et al., 2011c). Nevertheless, a systematic evaluation of hominin lower molars in the context of our 2D geometric morphometric series of analyses is still lacking (Martin G omez-Robles et al., 2007 G omez-Robles et al., , 2008 G omez-Robles et al., , 2011b). Therefore, the main objective of this study is to complete the geometric morphometric analysis of the postcanine dentition in order to investigate a more comprehensive scenario of hominin dental evolution during the Plio-Pleistocene. "
    [Show abstract] [Hide abstract] 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. Copyright © 2015 Elsevier Ltd. All rights reserved.
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