Eludicating the timing and pattern of changes in the skeleton is critical to an accurate understanding of ape and human evolution. It is implicitly assumed that apes and humans share a pattern of torso shape that appeared once in their shared ancestry as an adaptation to moving through the trees hanging below branches that differs from what is typical for quadrupedal monkeys, and that gibbons and spider monkeys are intermediate. However, a more complex pattern of variation among species appears to exist from photographs and illustrations. Despite being critical our interpretations about fossil ape and human evolution, variation in torso structure among primate species has never been characterized systematically, nor have hypothesized associations among torso elements or between individual bones and overall torso shape ever been tested statistically. The proposed research will characterize torso form in monkeys, apes and humans, quantify associations between torso shape, and shoulder, rib cage, lumbar and pelvic morphology in modern species, and use these new data to make informed inferences about the functional anatomy and evolution of fossil apes and human ancestors. This project has four specific aims: to (1) characterize pattern of torso shape in monkeys and apes for the first time using three dimensional reconstructions of CT scan data from intact cadavers, (2) quantify size and shape of isolated torso bones (humerus, pectoral girdle, ribs, sternum, vertebrae and pelvis) and correlate these data with the results of the analysis of intact torsos to identify aspects of bone form that reflect global torso structure, (3) assess the level of structural covariation among bones, and (4) apply these results to the interpretation of new fossil apes and early human ancestors, including a newly discovered pelvis of Dryopithecus brancoi, a 9 million year old ape from Hungary that is thought to be the closest fossil relative of the modern ape-human ancestor. The proposed research will provide 3D CT scan data for 40 primate torso skeletons on the web for public access, along with landmark coordinate and metric data for these cadavers and for a larger sample of skeletons. It will establish a new laboratory for three dimensional image analysis available to other students and faculty at University of Missouri, Columbia. This research will also provide hands-on research experience in evolutionary anatomy and 3D image analysis for graduate and undergraduate students, with underrepresented populations targeted for participation and mentored by a woman scientist.
