Matching Items (6)
Filtering by
- Creators: Barrett, The Honors College
- Creators: Reed, Kaye
Description
Despite the critical role that the vertebral column plays in postural and locomotor behaviors, the functional morphology of the cervical region (i.e., the bony neck) remains poorly understood, particularly in comparison to that of the thoracic and lumbar sections. This dissertation tests the hypothesis that morphological variation in cervical vertebrae reflects differences in positional behavior (i.e., suspensory vs. nonsuspensory and orthograde vs. pronograde locomotion and postures). Specifically, this project addresses two broad research questions: (1) how does the morphology of cervical vertebrae vary with positional behavior and cranial morphology among primates and (2) where does fossil hominoid morphology fall within the context of the extant primates. Three biomechanical models were developed for the primate cervical spine and their predictions were tested by conducting a comparative analysis using a taxonomically and behaviorally diverse sample of primates. The results of these analyses were used to evaluate fossil hominoid morphology. The two biomechanical models relating vertebral shape to positional behaviors are not supported. However, a number of features distinguish behavioral groups. For example, the angle of the transverse process in relation to the cranial surface of the vertebral body--a trait hypothesized to reflect the deep spinal muscles' ability to extend and stabilize the neck--tends to be greater in pronograde species; this difference is in the opposite of the direction predicted by the biomechanical models. Other traits distinguish behavioral groups (e.g., spinous process length and cross-sectional area), but only in certain parts of the cervical column. The correlation of several vertebral features, especially transverse process length and pedicle cross-sectional area, with anterior cranial length supports the predictions made by the third model that links cervical morphology with head stabilization (i.e., head balancing). Fossil hominoid cervical remains indicate that the morphological pattern that characterizes modern humans was not present in Homo erectus or earlier hominins. These hominins are generally similar to apes in having larger neural arch cross-sectional areas and longer spinous processes than modern humans, likely indicating the presence of comparatively large nuchal muscles. The functional significance of this morphology remains unclear.
ContributorsNalley, Thierra Kénnec (Author) / Kimbel, William H. (Thesis advisor) / Reed, Kaye (Committee member) / Shapiro, Liza (Committee member) / Arizona State University (Publisher)
Created2013
Description
Mammary gland development in humans during puberty involves the enlargement of breast tissue, but this is not true in non-human primates. To identify potential causes of this difference, I examined variation in substitution rates across genes related to mammary development. Genes undergoing purifying selection show slower-than-average substitution rates, while genes undergoing positive selection show faster rates. These may be related to the difference between humans and other primates. Three genes were found to be accelerated were FOXF1, IGFBP5, and ATP2B2, but only the latter one was found in humans and it seems unlikely that it would be related to the differences between mammary gland development at puberty between humans and non-human primates.
ContributorsArroyo, Diana (Author) / Cartwright, Reed (Thesis director) / Wilson Sayres, Melissa (Committee member) / Schwartz, Rachel (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
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
Cancer rates in our nearest relatives are largely unknown. Comparison of human cancer rates with other primates should help us to understand the nature of our susceptibilities to cancer. Data from deceased primates was gathered from 3 institutions, the Duke Lemur Center, San Diego Zoo, and Jungle Friends primate sanctuary. This data contained over 400 unique individuals across 45 species with information on cancer incidence and mortality. Cancer incidence ranged from 0-71% and cancer mortality ranged from 0-67%. We used weighted phylogenetic regressions to test for an association between life history variables (specifically body mass and lifespan) and cancer incidence as well as mortality. Cancer incidence did not correlate with both body mass and lifespan (p>.05) however, cancer mortality did (p<.05). However, it is uncertain if the variables can be used as reliable predictors of cancer, because the data come from different organizations. This analysis presents cancer incidence rates and cancer mortality rates in species where it was previously unknown, and in some primate species, is surprisingly high. Microcebus murinus(grey mouse lemur) appear to be particularly vulnerable to cancer, mostly lymphomas. Further studies will be required to determine the causes of these vulnerabilities.
ContributorsWalker, William Charles (Author) / Maley, Carlo (Thesis director) / Boddy, Amy (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Craniofacial morphology in primates can vary on the basis of their diet because foods are often disparate in the amount and duration of force required to break them down. Therefore diet has the potential to exercise considerable selective pressure on the morphology of the masticatory system. The zygomatic arch is a known site of relatively high masticatory strain and yet the relationship between arch form and load type is relatively unknown in primates. While the relative position and robusticity of the arch is considered a key indicator of craniofacial adaptations to a mechanically challenging diet, and central to efforts to infer diet in past species, the relationships between morphology and diet type in this feature are not well established.
This study tested hypotheses using two diet categorizations: total consumption percent and food material properties (FMPs). The first hypothesis that cortical bone area (CA) and section moduli (bone strength) are positively correlated with masticatory loading tests whether CA and moduli measures were greatest anteriorly and decreased posteriorly along the arch. The results found these measures adhered to this predicted pattern in the majority of taxa. The second hypothesis examines sutural complexity in the zygomaticotemporal suture as a function of dietary loading differences by calculating fractal dimensions as indices of complexity. No predictable pattern was found linking sutural complexity and diet in this primate sample, though hard object consumers possessed the most complex sutures. Lastly, cross-sectional geometric properties were measured to investigate whether bending and torsional resistance and cross-sectional shape are related to differences in masticatory loading. The highest measures of mechanical resistance tracked with areas of greatest strain in the majority of taxa. Cross-sectional shape differences do appear to reflect dietary differences. FMPs were not correlated with cross-sectional variables, however pairwise comparisons suggest taxa that ingest foods of greater stiffness experience relatively larger measures of bending and torsional resistance. The current study reveals that internal and external morphological factors vary across the arch and in conjunction with diet in primates. These findings underscore the importance of incorporating these mechanical differences in models of zygomatic arch mechanical behavior and primate craniofacial biomechanics.
This study tested hypotheses using two diet categorizations: total consumption percent and food material properties (FMPs). The first hypothesis that cortical bone area (CA) and section moduli (bone strength) are positively correlated with masticatory loading tests whether CA and moduli measures were greatest anteriorly and decreased posteriorly along the arch. The results found these measures adhered to this predicted pattern in the majority of taxa. The second hypothesis examines sutural complexity in the zygomaticotemporal suture as a function of dietary loading differences by calculating fractal dimensions as indices of complexity. No predictable pattern was found linking sutural complexity and diet in this primate sample, though hard object consumers possessed the most complex sutures. Lastly, cross-sectional geometric properties were measured to investigate whether bending and torsional resistance and cross-sectional shape are related to differences in masticatory loading. The highest measures of mechanical resistance tracked with areas of greatest strain in the majority of taxa. Cross-sectional shape differences do appear to reflect dietary differences. FMPs were not correlated with cross-sectional variables, however pairwise comparisons suggest taxa that ingest foods of greater stiffness experience relatively larger measures of bending and torsional resistance. The current study reveals that internal and external morphological factors vary across the arch and in conjunction with diet in primates. These findings underscore the importance of incorporating these mechanical differences in models of zygomatic arch mechanical behavior and primate craniofacial biomechanics.
ContributorsEdmonds, Hallie Margaret (Author) / Reed, Kaye (Thesis advisor) / Schwartz, Gary (Committee member) / Vinyard, Chris (Committee member) / Arizona State University (Publisher)
Created2017
Description
There is little research on volunteer tourism to primate sanctuaries. The purpose of this study was to help fill this knowledge gap and gain insights into how animal sanctuaries with volunteers in Costa Rica can be improved operationally to strengthen their conservation efforts. My research questions were: 1. How does volunteer tourism with primates in Costa Rica affect volunteers? 2. How does this volunteer tourism affect Costa Rica’s environment? The methodology used was an exploratory qualitative design that included a literature review of previous research and case studies and a visit with interviews at a primate sanctuary in Costa Rica. The findings did not generate sufficient data to answer the first research question. I did find that altruism was a key factor in recruiting effective volunteers. The study also found that conservation in Costa Rica relies on volunteer tourism to fill a human resource gap. This research will allow sanctuaries in Costa Rica to respond better to protect biodiversity.
ContributorsCavalier, Rebecca (Author) / Chhetri, Nalini (Thesis director) / Castillo, Elizabeth (Committee member) / College of Integrative Sciences and Arts (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05