Doctoral Dissertation Research: Ontogeny of Long Bone Diaphyses in Immature Late Pleistocene Humans

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It has long been understood that human bone responds to physical activity by becoming stronger when an individual engages in high levels of physical activity, and weaker when an individual remains inactive and immobile. Physical anthropologists have often used this general principle when studying human skeletal remains to make inferences about the amount of physical activity a particular population was participating in during life. Previous studies of past populations have shown that different groups vary strongly in the strength of their bones, and hence, how much physical activity they were undertaking on a regular basis. For example, in contrast to populations of recent humans living in an urban environment, groups of individuals participating in a hunting and gathering lifestyle prior to agriculture have skeletons which reflect a very active lifestyle. The leg and arm bones of Neandertals and the earliest modern humans display great strength in contrast to more recent populations, which is likely a result of a physically demanding lifestyle with a large amount of populational mobility. But how do different populations come to vary in their degree of long bone strength? Are the differences seen in adult populations partially a reflection of activities prior to adulthood? When during growth do populational differences in bone strength emerge, and do all populations attain bone strength in the same pattern and at the same rate? With financial support supplied by the National Science Foundation, Libby Cowgill will examine these issues by analyzing the long bones of a large sample of recent human children and comparing their bone strength to a sample of Neandertal and early modern human children. Data for this project will be collected at museums in the United States, Europe, and Africa, through the use of a portable x-ray machine. A technique called cross-sectional geometry will be used to measure and quantify the amount and distribution of bone at the mid-shaft level of each bone. By examining the bone strength of over 800 children, the normal range of developmental variation for long bone strength will be established. Once this is known, the bones of Neandertal and early modern human children can be compared to the rate and pattern of growth in recent human children. Information provided by this project will shed light on the continuing debate regarding the origin of modern human behavior and biology. In addition, this research will provide the first analysis of variation in the growth of bone strength using a geographically diverse sample of children. This data has the potential to be of value to both the medical community and to clinical research, and ultimately enhance our current understanding of the interaction between growth and activity in both the past and present. In addition, this research is part of a dissertation project that will promote graduate student training by providing a solid basis of knowledge in the research techniques and theoretical background necessary for continuing a career in anthropological research.