Skeletal remains of past human populations provide invaluable windows onto the evolution of human morphology, as well as enhanced understanding of functional variation in modern human morphology, in part because the range of behavior in ancient humans was more varied than is seen today. Limb bones are especially important in this respect, as they dynamically respond to physical activity via a process called bone functional adaptation, or "BFA." As a result, arm and leg bones are often treated as a "behavioral proxies" that provide critical information about mobility, lifestyle change, and technological innovation in past populations. Evidence shows, however, that BFA is under some genetic control that regulates bone sensitivity to mechanical environment. Variation in long bone structure and associated function therefore may reflect genetic ancestry, as much as behavior.
The pelvis and skull vary in accordance with genetic expectations and can therefore reflect important aspects of population history (e.g., migration, divergence or population reduction). The primary question driving this dissertation research by doctoral student Gina Agostini (under the supervision of Dr. Brigitte Holt, University of Massachusetts Amherst) is whether the same is true of long bones, a question to be answered by comparing patterns of cranial and long bone variation among European populations and their South African descendants. Using caliper measurements and digitized bone casts, data will be collected on cranial and long bone shape for each population. These data will be analyzed using population genetics software to predict the genetic distances (relationships) among the populations under study. If long bones do reflect genetic variation, then the relationships produced by long bone shape should generally match those produced by the crania. If they do not match, this suggests that cranial and long bones primarily reflect different biological or environmental processes. Results will either advocate the novel use of long bones to infer population history or will reinforce their usefulness at discerning behavior (or other environmental stimuli).
Clarification as to whether long bones primarily reflect genetic or behavioral signals is crucial for studies of human origins which must routinely extract information from limited skeletal data. Furthermore, because BFA is the same process that regulates bone plasticity, maintenance and healing, this project will show whether our ancestry influences the response time of our bones to a new exercise regime, sport, or fracture. This research also supports growing public interest in ancestry, a trend evidenced by the wide popularity of commercial ancestry kits and genealogical programs. In addition to publicly accessible reports, data generated by this project will be integrated into a series of community-based lectures, social media interactions, public workshops, and lifelong learning opportunities already conducted by the researchers.
