Matching Items (8)
Description
Modern primate diet is well-studied because of its considerable influence on multiple aspects of morphology, including the shape of the facial skeleton and teeth. It is well-established that differences in craniofacial form influence feeding abilities by altering the nature of bite force production. Tooth morphology, likewise, has been shown to vary with diet across primates, particularly in the details of occlusal form. It has also been suggested that tooth form (e.g., tooth root size and shape and crown size) reflects, in part, the demands of resisting the stresses generated during feeding. However, while they are central to our efforts to infer diet in past species, the relationships between bite force production, craniofacial morphology and tooth form are not well-established. The current study is separated into two parts. In Part I, the hypothesis that crown size and root surface area are adapted to resist masticatory stress is evaluated by testing whether these features show correlated variation along the tooth row in a taxonomically diverse sample of primates. To further explore the adaptive nature of this correlation, pair-wise comparisons between primates with mechanically resistant diets and closely-related species consuming less resistant foods are performed. If crown size and root surface area covary along the tooth row, past research suggests they may be related to bite force. To test this hypothesis, Part II examines the variation of these dental characteristics in comparison to theoretically-derived bite force patterns along the tooth row. Results suggest that patterns of maximum bite force magnitude along the tooth row are variable both within and between species, underscoring the importance of individual craniofacial variation on masticatory force production. Furthermore, it is suggested that some adaptations traditionally associated with high bite force production (i.e., facial orthognathy) may increase anterior biting force at the expense of posterior biting force. Taken together, results from the current study reveal that both tooth root and crown size vary in conjunction with the mechanical properties of diet and with bite force patterns along the tooth row in anthropoids.
ContributorsLucas, Lynn (Author) / Spencer, Mark (Thesis advisor) / Schwartz, Gary (Committee member) / Kimbel, William (Committee member) / Arizona State University (Publisher)
Created2012
Description
The pattern and strength of genetic covariation is shaped by selection so that it is strong among functionally related characters and weak among functionally unrelated characters. Genetic covariation is expressed as phenotypic covariation within species and acts as a constraint on evolution by limiting the ability of linked characters to evolve independently of one another. Such linked characters are "constrained" and are expected to express covariation both within and among species. In this study, the pattern and magnitude of covariation among aspects of dental size and shape are investigated in anthropoid primates. Pleiotropy has been hypothesized to play a significant role in derivation of derived hominin morphologies. This study tests a series of hypotheses; including 1) that negative within- and among-species covariation exists between the anterior (incisors and canines) and postcanine teeth, 2) that covariation is strong and positive between the canines and incisors, 3) that there is a dimorphic pattern of within-species covariation and coevolution for characters of the canine honing complex, 4) that patterns of covariation are stable among anthropoids, and 5) that genetic constraints have been a strong bias on the diversification of anthropoid dental morphology. The study finds that patterns of variance-covariance are conserved among species. Despite these shared patterns of variance-covariance, dental diversification has frequently occurred along dimensions not aligned with the vector of genetic constraint. As regards the canine honing complex, there is no evidence for a difference in the pleiotropic organization or the coevolution of characters of the complex in males and females, which undermines arguments that the complex is selectively important only in males. Finally, there is no evidence for strong or negative pleiotropy between any dental characters, which falsifies hypotheses that predict such relationships between incisors and postcanine teeth or between the canines and the postcanine teeth.
ContributorsDelezene, Lucas (Author) / Kimbel, William H. (Thesis advisor) / Schwartz, Gary T (Committee member) / Spencer, Mark (Committee member) / Verrelli, Brian C (Committee member) / Arizona State University (Publisher)
Created2011
Description
Bioarchaeologists often use dental data and spatial analysis of cemeteries to infer the biological and social structure of ancient communities. This approach is commonly referred to as biological distance (“biodistance”) analysis. While permanent crown data feature prominently in these efforts, few studies have verified the accuracy of biodistance methods for recognizing child relatives using deciduous teeth. Thus, as subadults comprise an essential demographic subset of mortuary assemblages, deciduous phenotypes may represent a critical but underutilized source of information on the underlying genetic structure of past populations. The goal of the dissertation is to quantitatively analyze the developmental program underlying deciduous phenotypes and to evaluate their performance in accurately reconstructing known genealogical relationships. This project quantifies morphological variation of deciduous and permanent tooth crowns from stone dental casts representing individuals of known pedigree deriving from three distinct populations: European Canadians, European Australians, and Aboriginal Australians.
To address the paucity of deciduous-focused validation research, phenotypic distances generated from the dental data are subjected to performance analyses (biodistance simulations) and compared to genetic distances between individuals. While family-specific results vary, crown morphology performs moderately well in distinguishing relatives from non-relatives. Comparisons between deciduous and permanent results (i.e., Euclidean distances, Mantel tests, multidimensional scaling output) indicate that deciduous crown variation provides a more direct reflection of the underlying genetic structure of pedigreed samples. The morphology data are then analyzed within a quantitative genetic framework using maximum likelihood variance components analysis. Novel narrow-sense heritability and pleiotropy estimates are generated for the complete suite of deciduous and permanent crown characters, which facilitates comparisons between samples, traits, dentitions, arcades, antimeres, metameres, scoring standards, and dichotomization breakpoints. Results indicate wide-ranging but moderate heritability estimates for morphological traits, as well as low to moderate integration for characters within (deciduous-deciduous; permanent-permanent) and between (deciduous-permanent) dentitions. On average, deciduous and permanent homologues are more strongly genetically correlated than characters within the same tooth row. Results are interpreted with respect to dental development and biodistance methodology. Ultimately, the dissertation empirically validates the use of dental morphology as a proxy for underlying genetic information, including deciduous characters.
To address the paucity of deciduous-focused validation research, phenotypic distances generated from the dental data are subjected to performance analyses (biodistance simulations) and compared to genetic distances between individuals. While family-specific results vary, crown morphology performs moderately well in distinguishing relatives from non-relatives. Comparisons between deciduous and permanent results (i.e., Euclidean distances, Mantel tests, multidimensional scaling output) indicate that deciduous crown variation provides a more direct reflection of the underlying genetic structure of pedigreed samples. The morphology data are then analyzed within a quantitative genetic framework using maximum likelihood variance components analysis. Novel narrow-sense heritability and pleiotropy estimates are generated for the complete suite of deciduous and permanent crown characters, which facilitates comparisons between samples, traits, dentitions, arcades, antimeres, metameres, scoring standards, and dichotomization breakpoints. Results indicate wide-ranging but moderate heritability estimates for morphological traits, as well as low to moderate integration for characters within (deciduous-deciduous; permanent-permanent) and between (deciduous-permanent) dentitions. On average, deciduous and permanent homologues are more strongly genetically correlated than characters within the same tooth row. Results are interpreted with respect to dental development and biodistance methodology. Ultimately, the dissertation empirically validates the use of dental morphology as a proxy for underlying genetic information, including deciduous characters.
ContributorsPaul, Kathleen Siobhan (Author) / Stojanowski, Christopher M. (Thesis advisor) / Buikstra, Jane E. (Committee member) / Schwartz, Gary T. (Committee member) / Taylor, Jesse E. (Committee member) / Arizona State University (Publisher)
Created2017
Description
Dietary diversity is an important component of species’s ecology that often relates to species’s abundance and geographic distribution. Additionally, dietary diversity is involved in many hypotheses regarding the geographic distribution and evolutionary fate of fossil primates. However, in taxa such as primates with relatively generalized morphology and diets, a method for approximating dietary diversity in fossil species is lacking.
One method that has shown promise in approximating dietary diversity is dental microwear analyses. Dental microwear variance has been used to infer dietary variation in fossil species, but a strong link between variation in microwear and variation in diet is lacking. This dissertation presents data testing the hypotheses that species with greater variation in dental microwear textures have greater annual, seasonal, or monthly dietary diversity.
Dental microwear texture scans were collected from Phase II facets of first and second molars from 309 museum specimens of eight species of extant African Old World monkeys (Cercopithecidae; n = 9 to 74) with differing dietary diversity. Dietary diversity was calculated based on food category consumption frequency at study sites of wild populations. Variation in the individual microwear variables complexity (Asfc) and scale of maximum complexity (Smc) distinguished groups that were consistent with differences in annual dietary diversity, but other variables did not distinguish such groups. The overall variance in microwear variables for each species in this sample was also significantly correlated with the species’s annual dietary diversity. However, the overall variance in microwear variables was more strongly correlated with annual frequencies of fruit and foliage consumption. Although some variation due to seasonal and geographic differences among individuals was present, this variation was small in comparison to the variation among species. Finally, no association was found between short-term monthly dietary variation and variation in microwear textures.
These results suggest that greater variation in microwear textures is correlated with greater annual dietary diversity in Cercopithecidae, but that variation may be more closely related to the frequencies of fruit and foliage in the diet.
One method that has shown promise in approximating dietary diversity is dental microwear analyses. Dental microwear variance has been used to infer dietary variation in fossil species, but a strong link between variation in microwear and variation in diet is lacking. This dissertation presents data testing the hypotheses that species with greater variation in dental microwear textures have greater annual, seasonal, or monthly dietary diversity.
Dental microwear texture scans were collected from Phase II facets of first and second molars from 309 museum specimens of eight species of extant African Old World monkeys (Cercopithecidae; n = 9 to 74) with differing dietary diversity. Dietary diversity was calculated based on food category consumption frequency at study sites of wild populations. Variation in the individual microwear variables complexity (Asfc) and scale of maximum complexity (Smc) distinguished groups that were consistent with differences in annual dietary diversity, but other variables did not distinguish such groups. The overall variance in microwear variables for each species in this sample was also significantly correlated with the species’s annual dietary diversity. However, the overall variance in microwear variables was more strongly correlated with annual frequencies of fruit and foliage consumption. Although some variation due to seasonal and geographic differences among individuals was present, this variation was small in comparison to the variation among species. Finally, no association was found between short-term monthly dietary variation and variation in microwear textures.
These results suggest that greater variation in microwear textures is correlated with greater annual dietary diversity in Cercopithecidae, but that variation may be more closely related to the frequencies of fruit and foliage in the diet.
ContributorsShapiro, Amy Elissa (Author) / Reed, Kaye E (Thesis advisor) / Schwartz, Gary T (Committee member) / Ungar, Peter S. (Committee member) / Arizona State University (Publisher)
Created2015
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
Early hominins present an unusual pattern of sexual dimorphism. On one hand, the canine teeth of these species are weakly size-dimorphic, vertically short, and nonhoning, suggesting a social system characterized by infrequent, low-intensity intermale competition and monogamous pair-bonding. On the other hand, marked size variation in skeletal remains attributed to species of Australopithecus is thought to reflect strong body-mass dimorphism, which is more consistent with intense intermale competition. Reconciling these conflicting signals and understanding their adaptive significance is a major goal of paleoanthropology. This dissertation research contributes to this objective by investigating factors that may constrain or reduce canine height in extant anthropoid primates. Two hypotheses regarding the relationship between canine height and other elements of the masticatory system were tested using phylogenetic comparative methods. According to the first hypothesis, canine reduction is a pleiotropic by-product of changes in the sizes of other components of the dentition. With respect to canine height, the results of this study fail to support this idea. There is limited evidence for a relationship between basal canine crown dimensions and incisor and postcanine size, but significant interspecific correlations between these variables are not strong and are restricted primarily to the female maxillary dentition. These results indicate that if pleiotropy influences canine size, then its effects are weak. The second hypothesis proposes that canine reduction is a consequence of selection for increased jaw-muscle leverage. This hypothesis receives some support: there is a clear inverse relationship between canine height and the leverage of the masseter muscle in male anthropoids. Females do not exhibit this association due to the fact that dimorphism in muscle leverage is weak or absent in most anthropoid species; in other words, female muscle leverage tracks male muscle leverage, which is linked to canine height. Leverage of the temporalis muscle is not correlated with canine height in either sex. Two specimens of the 3.0-3.7-million-year-old hominin Australopithecus afarensis fall at or beyond the upper end of the great ape range of variation in masseter leverage, which is consistent with the idea that hominin canine evolution was influenced by selection for increased jaw-muscle leverage.
ContributorsScott, Jeremiah Ezekiel (Author) / Kimbel, William H. (Thesis advisor) / Schwartz, Gary T. (Committee member) / Spencer, Mark A. (Committee member) / Arizona State University (Publisher)
Created2010
Description
Differences in the postcanine dentition of primates likely represent dietary adaptations given that the teeth interact directly with foods during mastication. Among early hominins, changes to both molar and premolar morphology are purported to indicate consumption of foods differing in their material properties. Some early hominins, such as the robust australopiths, possess premolars that resemble molars with enhancements to the distal part of the tooth (i.e., the talonid), including additional cusps and/or expanded basins. Such molarized premolars are thought to indicate that these hominins were processing mechanically challenging foods; that is, food items that were either hard or tough. Hypotheses tested in this study evaluated the link between the degree of premolar molarization and consumption of mechanically challenging foods in extant primates. Surface anatomy of the distal-most mandibular premolar (the P4) was quantified using a combination of 3D scans of postcanine dental casts and craniodental landmark data collected from 541 individuals, representing 22 extant primate taxa with well-studied diets and known food material properties. Taxa with more mechanically challenging diets were expected to have premolars with expanded talonids and enlarged P4s (and/or molar rows) relative to several mechanically-relevant size proxies. Taxa consuming high proportions of structural carbohydrates were also expected to have postcanine teeth with high occlusal relief (RFI), sharpness (DNE), and complexity (OPCR). Taxa consuming harder food items were expected to have lower relief and higher complexity, with sharpness determined by the proportion of structural carbohydrates included in their diet. The work presented in this dissertation supports most of these expectations, though talonid expansion per se was not clearly linked to the consumption of any particular diet. Overall, taxa with more mechanically challenging diets generally had relatively enlarged premolars when compared to taxa with softer diets and also differed predictably in their occlusal topography. The results of this dissertation support the functional significance of P4 crown size and measures of dental topography as they relate to diet and have implications for improving dietary inferences from the fossil record.
ContributorsDaly, Elizabeth Susanne (Author) / Schwartz, Gary T (Thesis advisor) / Delezene, Lucas K (Committee member) / Kimbel, William H (Committee member) / Arizona State University (Publisher)
Created2021
Description
This dissertation examines microevolutionary changes in the Eastern Adriatic and hinterland during Roman imperialism, evaluating changing patterns of variation among indigenous groups with varying histories of acceptance or defiance to Roman rule. Despite the prevalence of Roman influence, trade, and the accommodating nature of Roman political authority administered through existing local leaders, Eastern Adriatic and hinterland peoples underwent significant cultural transformations. Unlike the Roman-allied Liburnians, Romanization was not a voluntary and amicable process for the resisting Delmatae, Histri, Japodes, and Pannonians. The violent experiences of locals during the late Republican Period and early Roman Empire, including death, enslavement, conscription, and displacement, contrast with the eventual integration of the region by the end of the Roman Empire, when their descendants were Roman citizens. These complex histories make it challenging to understand local identities and the impact of Romanization. Biological distance analyses of dental morphology from Liburnian, Delmatae, Japodes, and Pannonian samples representing 313 individuals dating to the Iron Age (c. 700- 400 BCE), and Roman Period (Roman Republic c. 200- 0 BCE; Roman Empire c. 1- 500 CE), were contextualized with archaeological data and classical research. Results indicated no significant differences within Eastern Adriatic and hinterland populations across the time periods. However, interpretations of the results for Roman Period Liburnians, descendants of Roman allies, suggest differentiation from contemporaneous Italic Romans. Conversely, the descendants of resisting populations were not statistically different from Roman Empire Italics, potentially influenced by their ancestors’ experiences of war affecting subsequent admixture, community formation, and adherence to prevailing norms.
Roman laws that managed access to advantageous status identities through marriage and citizenship may also explain the findings that all surveyed local populations demonstrate continuity between ancestors and descendants. The dynamic of being identified as Roman, and yet descending from the people who fought against Rome, is further discussed as a form of biological imperialism, consequentially shaping indigenous ancestral ties within a pan-regional Roman citizenry. While Roman multiculturalism is often considered exemplary of Antique Period diversity, Roman values prioritized diversity when it was advantageous and used pluralism to encourage cultural assimilation and define outsiders.
ContributorsLoewen, Tisa Nicolette (Author) / Stojanowski, Christopher (Thesis advisor) / Buikstra, Jane (Committee member) / Novak, Mario (Committee member) / Knudson, Kelly (Committee member) / Arizona State University (Publisher)
Created2024