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- All Subjects: Human Evolution
- All Subjects: paleontology
- Creators: Schwartz, Gary
Description
Many of the derived features of the human skeleton can be divided into two adaptive suites: traits related to bipedalism and traits related to encephalization. The cervical spine connects these adaptive suites and is itself unique in its marked lordosis. I approach human cervical evolution from three directions: the functional significance of cervical curvature, the identification of cervical lordosis in osteological material, and the representation of the cervical spine in the hominin fossil record.
ContributorsFatica, Lawrence Martin (Author) / Kimbel, William (Thesis director) / Reed, Kaye (Committee member) / Schwartz, Gary (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution and Social Change (Contributor) / School of Life Sciences (Contributor)
Created2014-05
Description
Early weaning, slow somatic and dental growth, and late age at reproduction are all part of a suite of energetic trade-offs that have shaped human evolution. A similar suite of energetic trade-offs has shaped the evolution of the indriid-palaeopropithecid clade, though members of this clade exhibit extremely fast dental development and nearly vestigial deciduous teeth. The development and functional occlusion of the primary postcanine dentition (i.e., deciduous premolars and molars) coincides with several life history parameters in great apes and indriids. This dissertation explored great ape dental macrowear, molar development in indriids, and molar size in lemurs with a broader goal of improving reconstructions of life history profiles in extinct primates. To this aim, macrowear and dental development were analyzed in apes and lemurs, respectively. Occlusal casts (six great ape species; N=278) were scanned to track mandibular fourth deciduous premolar (dp4) macrowear. Utilizing dental topographic analyses, changes in occlusal gradient and terrain were quantified. A subset of the great ape data (four species; n=199) was analyzed to test if differences in dp4 wear correlate with age at weaning. Using dental histology, molar development was reconstructed for Indri indri (n=1) and Avahi laniger (n=1). Life history and molar size data were collected from the literature. The results of this dissertation demonstrate that most great apes exhibited evidence of topographic maintenance, suggesting dp4s wear in a manner that maintain functional efficiency during growth and development; however, the manner in which maintenance is achieved (e.g., preservation of relief or complexity) is species specific. Dp4 macrowear is not correlated with age at weaning in great apes and is probably unreliable to reconstruct age at weaning in hominins. The pace of molar development in members of the indriid- palaeopropithecid clade did not correlate with body or brain size, an association present in several other primates. Associations of molar size with age at weaning suggest that expanding other developmental models (e.g., the inhibitory cascade) to life history is worth consideration. The broad variation in macrowear, dental development, and size highlights how the primary dentition may correlate with different life history parameters depending on the species and ecological setting, an important consideration when using teeth to reconstruct life history profiles.
ContributorsCatlett, Kierstin Kay (Author) / Schwartz, Gary (Thesis advisor) / Barton, Michael (Committee member) / Godfrey, Laurie (Committee member) / Reed, Kaye (Committee member) / Arizona State University (Publisher)
Created2016
Description
Crown Cercopithecoidea (Old World monkeys) share bilophodont molars characterized by four cusps arranged into two transversely-aligned pairs connected by crests or “loph(id)s”. This derived dental configuration provides a flexible template that has been modified in different lineages of Old World monkeys to meet the mechanical demands of food-processing in species with diverse and varied diets. This molar Bauplan evolved in the early stages of Old World monkey evolution, and one consequence of these morphological changes in occlusal morphology relative to apes and more basal catarrhines is a set of distinct patterns of tooth wear. Adaptive explanations for the origins of bilophodonty have emphasized dietary reconstructions but have not explored the implications of molar crown reorganization on the interaction between tooth wear and tooth function. This study combines description of new fossil material of early Miocene stem cercopithecoids and 3D dental topographic analyses of cross-sectional M2 wear series of extant catarrhines (n=511, 24 species) and Miocene fossil catarhines (n=81, 7 genera) to explore how functional aspects of molar topography are altered by tooth wear, to test whether the acquisition of bilophodont molars resulted in distinct occlusal topographies and patterns of topographic change with wear among Old World monkeys, and to determine whether differences in patterns of topographic change with wear reflect differences in diet.Descriptions of new fossils of the early Miocene stem cercopithecoid Noropithecus bulukensis confirm its generic distinction from Victoriapithecus macinnesi and highlight the dental metric and morphological variation that complicates identification of isolated teeth. Results of dental topographic analyses show that wear-mediated patterns of change in functional topographic metrics do not reflect broad dietary differences in extant catarrhines. While topographic features of unworn molars exhibit a phylogenetic signal, the pattern of wear-mediated topographic change does not. Molar topography of victoriapithecids is similar to extant cercopithecids with frugivorous and hard-object feeding diets, supporting previous dietary reconstructions. Victoriapithecid molar occlusal surfaces exhibit less complexity, less curvature, and higher relief than proconsulids prior to heavy wear stages. They are not distinct from occlusal topographies of small-bodied non-cercopithecoid catarrhines at any wear stage. Overall, these results suggest that the acquisition of bilophodont molar morphology in early and middle Miocene stem cercopithecoids was not associated with a shift in occlusal topography relative to more basal catarrhines. Rather, it is among proconsulids that shifts toward more complex, higher curvature occlusal surfaces are found.
ContributorsLocke, Ellis (Author) / Reed, Kaye (Thesis advisor) / Schwartz, Gary (Committee member) / Kelley, Jay (Committee member) / Arizona State University (Publisher)
Created2021