Doctoral Dissertation Improvement: 3-D Modeling of Lung Volume from Thoracic Form: A Geo-Morphometric Baseline for the Study of Thoracic Patterning in the Human Fossil Record

University Of Iowa, Iowa City IA

Investigators

Abstract

Since the last half of the past century, Bergmann's Rule has been the working hypothesis under which most aspects of Neandertal postcranial anatomy have been explained. Consequently, the Neandertal's reputed barrel-shaped thorax has been historically viewed as responsive to the need to conserve energy in the form of heat during the height of the last glacial maximum. However, climate is not the only factor that may affect thoracic patterning. Mode of locomotion, pulmonary fitness and activity patterns, as well as other related dynamics may have affected the overall thoracic bauplan. Despite the emphasis placed on ecogeographical explanations, few attempts have been made to quantitatively assess the adaptive significance of variation in chest size and shape across species within the genus Homo. Furthermore, critical gaps remain in our understanding of important aspects of modern thoracic geometry and its relation to ventilation, energetics, and climatic adaptation within living populations. Accordingly, this study examines the three dimensional relationships between skeletal thoracic form and respiratory variables in living humans to advance our understanding of how variation in thoracic form impact pulmonary output. To test the influence of skeletal thoracic shape on respiratory variables (e.g., total lung capacity, functional residual capacity, etc.) investigators will quantify variation in thoracic morphology within a mixed-sex computed tomography (CT) sample of 50 respiratorily normal subjects and 10 subjects with putative barrel-shaped chests from chronic obstructive pulmonary disorder (COPD), all between the ages of 20 and 60 (originally collected under IRB: 199708651). Results from this homogenous, living CT sample will then be compared to a regionally heterogeneous, mixed-sex skeletal sample from the extremes of recent human variation (n=134), as well as the more complete Neandertal specimens Kebara 2, Tabun C1, Shanidar 3, and La Chapelle, in order to estimate respiratory variables. This analysis will be achieved through the use of three dimensional geometric landmarks on the axial skeleton of both samples, as well as the costochondral cartilages (in the living sample) in order to characterize individual rib curvature and overall thoracic geometry, in conjunction with lung function test variables from the living sample. This study uniquely integrates clinical and anthropological methodologies to address issues that have been studied extensively by clinicians. The results obtained from this study will provide a baseline for future studies of modern and fossil human thoracic adaptation. Moreover, since thoracic development and pulmonary capacity/ventilation are associated; a thorough understanding of this relationship is crucial to treating problems associated with abnormal thoracic development in living populations (e.g., ankylosing spondylitis, severe cerebral palsy, spinal muscular atrophy, chest wall reconstruction, etc.), poor lung/thoracic concordance (such as is the case in COPD) and/or lung transplantation. This connection to clinical and anatomical studies is crucial in biological anthropology and paleoanthropology. Explicitly bridging these complimentary disciplines provides a greater appreciation of human variation that benefits both academics and applied anthropologists alike.