Faculty Bibliography

Secondary intracortical remodeling of bone varies considerably among and within vertebrate skeletons. Although prior research has shed important light on its biomechanical significance, factors accounting for this variability remain poorly understood. We examined regional patterning of secondary osteonal bone in an ontogenetic series of wild-collected primates, at the midshaft femur and humerus of Chlorocebus (Cercopithecus) aethiops (n = 32) and Hylobates lar (n = 28), and the midshaft femur of Pan troglodytes (n = 12). Our major objectives were: 1) to determine whether secondary osteonal bone exhibits significant regional patterning across inner, mid-cortical and outer circumferential cortical rings within cross-sections; and if so, 2) to consider the manner in which this regional patterning may reflect the influence of relative tissue age and other circumstances of bone growth. Using same field-of-view images of 100-microm-thick cross-sections acquired in brightfield and circularly polarized light microscopy, we quantified the percent area of secondary osteonal bone (%HAV) for whole cross-sections and across the three circumferential rings within cross-sections. We expected bone areas with inner and middle rings to exhibit higher %HAV than the outer cortical ring within cross-sections, the latter comprising tissues of more recent depositional history. Observations of primary bone microstructural development provided an additional context in which to evaluate regional patterning of intracortical remodeling. Results demonstrated significant regional variability in %HAV within all skeletal sites. As predicted,%HAV was usually lowest in the outer cortical ring within cross-sections. However, regional patterning across inner vs. mid-cortical rings showed a more variable pattern across taxa, age classes, and skeletal sites examined. Observations of primary bone microstructure revealed that the distribution of endosteally deposited bone had an important influence on the patterning of secondary osteonal bone across rings. Further, when present, endosteal compacted coarse cancellous bone always exhibited some evidence of intracortical remodeling, even in those skeletal sites exhibiting comparatively low %HAV overall. These results suggest that future studies should consider the local developmental origin of bone regions undergoing secondary remodeling later in life, for an improved understanding of the manner in which developmental and mechanical factors may interact to produce the taxonomic and intraskeletal patterning of secondary bone remodelling in adults

OBJECTIVE: Our objective is to exploit architectural constraint for the analysis and interpretation of craniofacial form, which we apply here to the reconstruction of the early Homo cranium KNM-ER 1470. We are motivated to perform this study because in the absence of biological criteria our preconceptions are likely to govern our concept of craniofacial form. STUDY DESIGN: We reassembled the fragmented parts--left and right halves of the calvaria and the face--according to mammalian craniofacial architectural constraints described by Donald H. Enlow and colleagues. RESULTS: When evaluated on a biological premise, KNM-ER 1470 is found to have a more prognathic midface than commonly appreciated. The relationship between facial prognathism and cranial capacity also provides an estimate downward for this specimen, from 752cc to ca. 700cc. CONCLUSION: Awareness of our preconceptions is critical to the performance of relatively unbiased research in fields characterized by interpretations of morphology. When perceptual bias is relatively minimized, applied here as an architecturally constrained of KNM-ER 1470 craniofacial skeleton, we are able to provide the scientific community with a more tractable Gestalt perspective of form