Matching Items (12)
Description
This study examined the ontogeny of body mass (i.e. "growth") of Otolemur garnettii and Galago senegalensis. Growth is a proximate causal mechanism for adult size variation and growth patterns themselves can be the target of selection with adult size being the end result. Therefore, growth patterns of species can be the result of adaptation to species-specific social system, ecology, and life-history. The goals of this study were to: (1) Assess whether interspecific body mass variation was due to differences in growth rate, growth duration, a combination of the two, or neither; (2) test the hypothesis that sexual size dimorphism is attained by differences in relative growth rate as predicted by sexual selection theory; and (3) test the hypothesis that frugivorous O. garnettii grow at a relatively lower rate than gummivorous Go. senegalensis as predicted by an ecological risk aversion hypothesis. Growth rates and durations of Otolemur garnettii and Galago senegalensis males and females were compared both interspecifically and intraspecifically. The hypotheses regarding the ontogeny of sexual size dimorphism and the risk aversion hypothesis were not supported. O. garnettii males and females grow at an absolutely higher rate and for a longer duration compared to Go. senegalensis males and females respectively. O. garnettii females grow at a relatively higher rate compared to Go. senegalensis females as well. This may relate to weaning habits. O. garnettii infants are weaned during the dry season when feeding competition would be presumably high making large mass at weaning advantageous. While the growth of females might be strongly influenced by natural selection and competition for resources following weaning, the growth of males may be more strongly influenced by sexual selection relating to contest competition for females. Sexual size dimorphism results from differences in growth duration in O. garnettii and from differences in both growth duration and growth rate in Go. senegalensis. The results of this study highlight the need for more data on the growth patterns, mating and social systems, feeding competition, and life history schedules for these and other galagids. Study of how and why growth patterns have diverged through evolution is important in discerning the evolutionary history of each species.
ContributorsSchaefer, Melissa K (Author) / Nash, Leanne T. (Thesis advisor) / Marzke, Mary W. (Committee member) / Schwartz, Gary T. (Committee member) / Arizona State University (Publisher)
Created2011
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
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
As the junction between the head and the trunk, the neck functions in providing head stability during behaviors like feeding to facilitating head mobility during behavior like grooming and predator vigilance. Despite its importance to these vital behaviors, its form and function remain poorly understood. Fossil hominin cervical vertebrae preserve a striking diversity in form despite the commitment to orthograde bipedality. Do these differences in cervical vertebral form correspond to functional variations among our recent ancestors? This dissertation attempts to understand 1) how does the neck function in head stability and mobility 2) how do these functions relate to cervical vertebral form. Kinematic and passive range of motion studies were conducted in several species of primate to obtain measures of function which were subsequently related to skeletal form.
Results show that cervical vertebral morphology does not significantly covary with differences in joint mobility. Rather, they implicate the critical role of ligaments and muscles in facilitating head mobility. Results of the kinematics study show that the neck plays a role in maintaining head stability during locomotion. However, the kinematic data do not significantly correlate with morphological variation among primate species. Given the negative results of the extant morphological analyses, it is difficult to apply them to the fossil record. As such, the functional significance of the disparate morphologies found in the hominin fossil record remain ambiguous.
Results show that cervical vertebral morphology does not significantly covary with differences in joint mobility. Rather, they implicate the critical role of ligaments and muscles in facilitating head mobility. Results of the kinematics study show that the neck plays a role in maintaining head stability during locomotion. However, the kinematic data do not significantly correlate with morphological variation among primate species. Given the negative results of the extant morphological analyses, it is difficult to apply them to the fossil record. As such, the functional significance of the disparate morphologies found in the hominin fossil record remain ambiguous.
ContributorsGrider-Potter, Neysa (Author) / Kimbel, William (Thesis advisor) / Raichlen, David (Committee member) / Schwartz, Gary (Committee member) / Ward, Carol (Committee member) / Arizona State University (Publisher)
Created2019
Description
Previous studies have demonstrated that cranial base anatomy is influenced primarily by three different characteristics: brain shape, positional behavior, and facial growth (Lieberman et al. 2000). Although the timing of cranial base growth is not fully understood, features of the cranial base are frequently used to interpret the hominin fossil record (Guy et al. 2005; White et al. 1994; Brunet et al. 2002). While specific aspects of cranial base morphology may be species-specific, there is sparse information on the developmental mechanisms driving these adult morphologies. The aim of this study is to 1) examine changes in the human cranial base form throughout ontogeny and 2) determine their relationship to the development of positional behavior and brain growth. This research asks: to what extent does human cranial base morphology vary before and after adult positional behavior is acquired? The null hypothesis is that there is no relationship between features of the cranial base and the development of positional behavior. Data are collected using 3D landmarks on n=35 human crania and analyzed with both Morphologika (O'Higgins and Jones 1999) and MorphoJ (Klingenberg 2011) to identify age related changes in shape. Results of this study demonstrate that most of the changes in cranial base form occur between dental eruption stages N and NJ1 between 0 and 2 years of age. These changes consist of a relative shortening of the anterior-posterior cranial base length, a more posterior positioning of the foramen magnum, and a more anterior position of the occipital condyles and separate the N and NJ1 dental development groups from other groups. This change coincides with the transition to upright posture in human children (Abitbol 1993), a significant period of brain growth (Neubauer 2009) and has implications for reconstructing positional behavior in fossil hominins. Despite new insights into the development of cranial base morphology, the utility of the cranial base in assigning hominin taxonomy remains inconclusive.
ContributorsMcgechie, Faye Rachele (Author) / Kimbel, William (Thesis director) / Schwartz, Gary (Committee member) / Hill, Cheryl (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2015-05
Description
Mammals with a habitually orthograde trunk posture possess a more anterior foramen magnum than mammals with non-orthograde trunk postures. Russo & Kirk (2013) also found that bipedal orthograde mammals possess a more anteriorly placed foramen magnum than those that are just habitually orthograde. This finding has allowed us to use foramen magnum position as a predictor of trunk posture in early hominins. This prompts more research of how the other landmarks on the cranial base move in relation to this shift in foramen magnum positioning. I collected landmark data on images of 125 mammalian basicrania spanning 41 species that differed in trunk posture. Using Procrustes and Principal Components Analysis (PCA), I attempted to evaluate the effects of trunk posture on basicranial morphology, primarily focusing on the placement of the carotid and jugular foramina. The results supported Russo and Kirk's finding of a more anterior foramen magnum placement in orthograde mammals; in addition, the results displayed correlations between foramen magnum position and carotid foramen position among primates and diprotodonts.
ContributorsPena, Angela (Author) / Kimbel, William (Thesis director) / Schwartz, Gary T. (Committee member) / Barrett, The Honors College (Contributor) / School of Human Evolution and Social Change (Contributor)
Created2015-05
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
I argued that the development of the Anterior Inferior Iliac Spine (AIIS), an entirely novel trait unique to the hominin pelvis, signaled a critical transformation from facultative (occasional) to obligate (exclusive) bipedality. The species that were considered included Homo sapiens, Australopithecus afarensis (Lucy), Ardipithecus ramidus (Ardi) and Pan troglodytes (chimpanzee); Ar. ramidus is believed to have been a facultative biped while both A. afarensis and H. sapiens were/are obligate bipeds, a stark contrast from the upright Bent-Hip Bent-Knee gait seen in chimpanzees, an organism that lacks an AIIS. It was found that the AIIS served a significant function in the advent of bipedality from Pan to Ardi because it allowed higher attachment for the rectus femoris muscle, a crucial knee extensor; however it is not heavily implicated in the transformation from facultative to obligate bipedality. Moreover, the appearance of the AIIS, first seen in Ardi, likely occurred following the lumbosacral changes that positioned the hominin body in an upright position so that the body's center of mass remained balanced over its supporting base. This provided the framework necessary to further select for organisms that had the AIIS and could walk upright, which perpetuated this change in the hominin lineage.
ContributorsGalibov, Michael (Author) / Kimbel, William (Thesis director) / Jacobs, Mark (Committee member) / School of Life Sciences (Contributor) / School of Human Evolution and Social Change (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
This dissertation begins to lay out a small slice of the history of morphological research, and how it has changed, from the late 19th through the close of the 20th century. Investigators using different methods, addressing different questions, holding different assumptions, and coming from different research fields have pursued morphological research programs, i.e. research programs that explore the process of changing form. Subsequently, the way in which investigators have pursued and understood morphology has witnessed significant changes from the 19th century to modern day research. In order to trace this shifting history of morphology, I have selected a particular organ, teeth, and traced a tendril of research on the dentition beginning in the late 19th century and ending at the year 2000. But even focusing on teeth would be impossible; the scope of research on this organ is far too vast. Instead, I narrow this dissertation to investigation of research on a particular problem: explaining mammalian tooth morphology. How researchers have investigated mammalian tooth morphology and what counts as an explanation changed dramatically during this period.
ContributorsMacCord, Katherine (Author) / Maienschein, Jane (Thesis advisor) / Laubichler, Manfred (Thesis advisor) / Laplane, Lucie (Committee member) / Kimbel, William (Committee member) / Creath, Richard (Committee member) / Hurlbut, Benjamin (Committee member) / Arizona State University (Publisher)
Created2017
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