No abstract

Due to a general, though undocumented, sense that little diagnostic information can be gleaned from them, ribs and overall thoracic morphology have been comparatively understudied relative to other anatomical regions in human paleontology. This pilot study tests the influence of skeletal thoracic shape on respiratory variables (e.g., total lung capacity, functional residual capacity, etc.) using computed tomography (CT), to expand our understanding of modern and Neandertal thoracic patterning. The mixed‐sex CT sample consists of 25 respiratorily normal subjects and 10 subjects with chronic obstructive pulmonary disorder (COPD), all between the ages of 20 and 60. This homogenous, living CT sample is compared with a regionally heterogeneous, mixed‐sex skeletal sample from the extremes of human climatic distribution (n=48), as well as the Levantine Neandertal specimens Kebara 2 (original) and Tabun C1 (cast). Preliminary results suggest that, while gross spirometric measures, such as total lung capacity, agree well with the predicted model, further study is needed to delineate the skeletal parameters most amenable to comparison for such variables as functional residual capacity. Additionally, comparisons of the Levantine Neandertals with the modern sample fail to demonstrate any significant temporal excursion from the range of modern variability with respect to these parameters.

Unlike their cervical counterparts, supernumerary lumbar ribs are generally considered to be of little clinical significance, though they do constitute a topic of anthropological interest. The two most complete Neandertal lumbar regions (Kebara 2 and Shanidar 3) both show evidence of articular facets for bilateral lumbar ribs and a high incidence of the condition has been reported in the prehistoric Sadlermiut Eskimo. This pilot study tests the association of bi‐iliac breadth with the presence of supernumerary lumbar rib in two wide‐bodied prehistoric populations: Pt. Hope Inupiat (n=25), Tierra del Fuegan/Aonikenk (n=25), and one narrow‐bodied prehistoric population: South African Zulu (n=25). Moreover, as mouse models have shown a correlation between 12th rib length and lumbar rib presence, this was also investigated. Of the populations studied, only the Pt. Hope Inupiat evinced lumbar ribs (16%) even though their bi‐iliac breadth was not significantly greater than that seen in the Tierra del Fuegan/Aonikenk. Additionally, significantly longer ribs were observed for the Pt. Hope Inupiats in agreement with the predicted model. These results suggest that the presence of supernumerary lumbar rib in human prehistory is indicative of other basic alterations of the axial skeleton and is most likely related to population history.Grant Funding Source: National Science Foundation Doctoral Dissertation Improvement Grant #0752723 and the Wenner‐Gren Foundation for Anthropological Research.

Within the context of human evolution, differences in rib cross‐sectional shape have been explained as a means of preserving equivalent pulmonary function in differently shaped thoraces during respiratory excursions (Jellema et al., 1993.). Relatively flat ribs should then be associated with a narrower trunk (modern), whereas rounded ribs should accompany a thorax that is transversely broad ("archaic"). This study tests whether the more modest variation in thoracic shape within living humans related to climatic adaptation may also elicit these differences. To test the influence of thoracic form on individual rib cross‐sectional shape, external shape data was collected from the 4th and 8th ribs of males from within two ecogeographically distinct populations: Inuit (n=20) and Zulu (n=20). Overall thoracic shape at each level was characterized using measures modified from Franciscus and Churchill (2002), and external rib shaft molding was used to capture cross‐sectional shape. The 2‐D outline of each cross‐section was acquired using TPS software (Rohlf, 2007). As predicted, the Inuits, with their wider torso, are determined to have statistically significantly rounder ribs, accounted for by greater medio‐lateral dimensions, though not greater cross‐sectional area. Results are presented in the context of climatic adaptation, as well as previous considerations regarding rib shape and resistance to bending.Research funded with generous support from University of Iowa Student Government, UI Graduate Student Senate, Center for Global and Regional Environmental Research, the Stanley ‐UI Foundation Support Organization.Grant Funding SourceUniversity of Iowa Student Government, UI Graduate Student Senate, Center for Global and Regional Environmental Research, the Stanley –UI Foundation Support Organization