<p>There has been a trend toward decreasing skeletal robusticity in the genus Homo throughout the Pleistocene, culminating in the gracile postcrania of living modern humans. This change is typically attributed to changing tool technologies and subsistence patterns among human groups. However, other mammalian groups also experience a similar change in their postcranial strength over the same time period. It is proposed in this dissertation that ecological variables are correlated with measures of postcranial strength and may be a better explanation for Holocene skeletal gracilization in humans, as well as in other mammalian genera. This hypothesis is investigated through a close examination of the scaling patterns in two extant genera, Canis and Ursus, and a comparison of scaling patterns and relative strength of different species of Canis, including a fossil species that provides information about temporal change. Measurements of limb length, joint surface area, bone diameter, and strength measurements derived from radiographic images of long bone midshafts of North American specimens of Canis, (including the fossil Canis dirus) and Ursus were collected. Scaling patterns of the cross-sectional variables on limb length and joint surfaces were analyzed for the interspecific and intraspecific samples. </p><p>The first hypothesis tested was that Canis scales with geometric similarity of cross-sectional variables on bone length and body mass, and the Ursus scales with elastic similarity. Larger Canis have relatively stronger postcrania than smaller Canis. The primary way in which this strength is achieved in larger individuals is through a relatively shortening of the bone length. The second hypothesis tested was that postcranial strength is correlated with ecological variables. To investigate this hypothesis, scaling patterns of different species of Canis were compared, including the fossil dire wolf. The results show that the dire wolf is relatively stronger than its living congenerics. There is also a strong relationship between the ratio of prey body mass to predator body mass and relative strength for these species. Carnivores that are hunting animals much larger than themselves must have postcranial skeletons that are strong enough to withstand the loading of the skeleton that occurs during hunting, taking down, and processing large herbivores.</p> / Dissertation

Human body size and limb proportions can provide important information about adaptation, population movements, and health disparities. This study investigated changes in body size and limb proportions of adult Egyptians temporally and geographically in relation to climatological, sociopolitical and economic developments. It was predicted that Egyptian groups that experienced more environmental stress would be shorter and exhibit less sexual dimorphism. It was also predicted that Egyptians would be intermediate between higher and lower latitude populations in body form and limb length ratios. The main skeletal sample consisted of 492 males and 528 females, all adults from the Predynastic and Dynastic Periods, a time spanning c. 5500 BCE-600 CE. Egyptian body dimensions were compared to Nubian groups, as well as to modern Egyptians and other higher and lower latitude populations. The present study found a downward trend in ancient Egyptian stature for both sexes through time, as well as decreased sexual dimorphism in stature. The decreases may be associated with dietary and social stress with the intensification of agriculture and increased societal complexity. Modern Egyptians in the study's sample are generally taller and heavier than their predecessors; however, modern Egyptians exhibit relatively lower sexual dimorphism in stature. Ancient Egyptians have more tropically adapted limbs in comparison to body breadths, which tend to be intermediate when plotted against higher and lower latitude populations. These results may reflect the greater plasticity of limb lengths compared to body breadth. The results might also suggest early Mediterranean and/or Near Eastern influence in Northeast Africa.

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