EXPERIMENTAL INVESTIGATIONS OF BLUNT FORCE TRAUMA IN THE HUMAN SKELETON By Mariyam I. Isa A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Anthropology—Doctor of Philosophy 2020 ABSTRACT EXPERIMENTAL INVESTIGATIONS OF BLUNT FORCE TRAUMA IN THE HUMAN SKELETON By Mariyam I. Isa In forensic anthropology, skeletal trauma is a growing area of analysis that can contribute important evidence about the circumstances of an individual’s death. In bioarchaeology, patterns of skeletal trauma are situated within a cultural context to explore human behaviors across time and space. Trauma analysis involves transforming observations of fracture patterns in the human skeleton into inferences about the circumstances involved in their production. This analysis is based on the foundational assumption that fracture behavior is the nonrandom result of interactions between extrinsic factors influencing the stresses placed on bone and intrinsic factors affecting bone’s ability to withstand these stresses. Biomechanical principles provide the theoretical foundation for generating hypotheses about how various extrinsic and intrinsic factors affect the formation of fracture patterns, and about how these factors can be read from fracture patterns. However, research is necessary to test and refine these hypotheses and, on a more basic level, to document the relationships between “input” variables of interest and fracture “outputs.” One research approach involves the use of forensic and/or clinical case samples. Case- based approaches are important because they provide data from real scenarios and contexts that may be similar to those encountered in unknown cases. However, a limitation is that input variables are not directly measured or controlled and therefore cannot be precisely known. Therefore, case-based approaches offer incomplete means of hypothesis testing. Over the past decade, anthropologists have increasingly addressed this problem using prospective, experimental approaches. Experimental research provides the advantage of investigating fracture patterns generated under known, replicable, laboratory-controlled conditions. While this type of research is believed to be most applicable to forensic cases when it is conducted on unembalmed postmortem human subjects (PMHS) within the perimortem interval, to date the majority of experimental studies have involved nonhuman models. Given micro- and macro-structural differences between species, it is yet unknown how results obtained in nonhuman bones scale to human bones. Experimental studies on PMHS are therefore warranted to test hypotheses and develop reference points for how fracture patterns form in response to various loading inputs. The purpose of this dissertation is to document and evaluate basic relationships between several forensically relevant input variables and fracture behavior outputs through a series of blunt force impact experiments on human crania and femora. Part one of this dissertation investigates cranial fracture behavior in relation to the input variables of point of impact, number of impacts, impact surface, and kinetic energy. Part two investigates the relationship between impact direction and fracture behavior in the femur. The papers comprising this dissertation are united by three common goals: 1) to investigate fracture formation, including how and where fractures initiate and propagate relative to the impact site; 2) to document and compare fracture behavior in response to known input variables; and 3) to evaluate fracture features described in reference literature and gather evidence of their utility in reconstructing these input variables. This research advances understanding of the interplay between impact variables and fracture behavior in cranial and postcranial blunt force skeletal trauma. Furthermore, this study contributes reference data associating known loading conditions with resultant fracture patterns in human material. This type of data is necessary to build interpretive and methodological theory in anthropological trauma analyses. For my parents, thank you for everything. I love you. I would also like to dedicate this dissertation to those who donated their bodies to science. Without the selfless generosity of these individuals and their families, this research would not have been possible. iv ACKNOWLEDGMENTS This dissertation would not have been possible without the support of my mentors, family, friends, and colleagues. As I reflect on the journey that brought me here, there are so many people for whom I feel intense gratitude. I would first like to thank my committee members, Drs. Fenton, Hefner, Wei, and Wrobel for freely and generously giving of their help, advice, and insight. I am a better scholar for the lessons they taught me and the discussions we had over the years. To my chair, Dr. Todd Fenton, thank you for taking a chance on me so many years ago. From the beginning you believed in me, treated me as a serious researcher, and gave me every opportunity to help me achieve my dream. These are gifts I hope to pay forward to my future students as I help them achieve their own dreams. In addition to my committee, I am grateful to the others who mentored and helped me throughout my journey. Dr. Lynne Goldstein, thank you for giving me something to believe in when I needed it most. Your grace, intelligence, and fierce loyalty to your students inspire me. I will always cherish our Soup Spoon breakfasts. Dr. Stacey Camp, thank you for sharing your expertise and experience, for being unwaveringly open and honest about all things academic, and for being generous with your time and advice. Dr. Norm Sauer, thank you for helping to spark my interest in forensic anthropology and for tempering this passion with the wisdom that there is more to life than this field or this job. Cliff Beckett, engineering technician extraordinaire, thank you for your patience, your humor, and your ability to fix all things mechanical. Without your expertise, the experiments on which this dissertation were based would not have been possible. Joan Reid, our department’s Graduate Secretary, thank you for your unparalleled commitment to students, for keeping us all on track, and for answering my many questions over the years. v I owe so much to my family, who have loved me, supported me, and cheered me on my entire life. To my mom and dad, Paula and Shahrin Isa, thank you for everything. Thank you for making me curious and persistent, for teaching me to stand up for myself, and for always listening with great interest as I ramble about the things that fascinate me most. Thank you for letting me find my own way, for always welcoming me home, and for never making me question whether you are proud of me. I am so lucky to have such amazing people as my parents. To my brother, Gabe, thank you for being my lifelong best friend. You are the coolest person I know and I am so proud of you. Finally, to my grandparents, Norma and George Johnston, thank you for your unwavering support and confidence in me. Grandpa, even though you are no longer here I have felt your presence every step of the way. I hope I am making you proud. I am extremely grateful to Giacomo Fontana, who raised my spirits and encouraged me when I needed it most. Thank you for being the first to celebrate the smallest of my accomplishments, for holding space for me when I struggle, and for teaching me to take life less seriously. Grazie mille. I would not have made it through this process without my friends. I have the best friends in the world; they inspire me every day. While I have many to thank, a few stand out. Dr. Amy Michael, I would not be the human or the anthropologist I am today without you. I am so grateful for your love, your loyalty, and your brilliant mind. Dr. Susan Kooiman, you are one of the strongest people I know. I am in constant awe of your ability to get things done and make it look easy. Thank you for coffee shop work dates, Crunchy’s karaoke nights, and countless other adventures. Jack Biggs (and Kevin the border collie), thank you for brightening my life with laughs, plants, pastries, and puppy snuggles. Dr. Lisa Bright, thank you for being my go-to source for advice, obscure information, and the latest news. Your mind is a treasure trove and I vi am lucky to have had glimpses inside. Emily Milton, I am thankful for the times we spent contemplating the mysteries of life, the universe, and anthropology. I will cherish our conversations – the intense and the intensely silly – forever. Autumn Painter and Jeff Painter, your friendship has meant so much to me. From the bottom of my heart, thank you for all the kind gestures that kept me afloat over the years. Betsy Woldeyohannes, you have a beautiful soul and a deeply compassionate heart. My life is better for having you in it. I aspire to see the world with as much depth and clarity as you do. To my dear friends Gocha et al. (Dr. Tim Gocha, Kelsey Carpenter, Erica Christensen, Abbie Grande, Dr. Janet Finlayson, Justin Maiers, and Ryan Strand), thank you for keeping me laughing and for your intense friendship. You are some of the smartest and most raucous people I know. I know I can always count on you for inspiring conversations about life and science, for the worst jokes and best limericks, and for a reliably and undeniably good time. My friends outside of anthropology have been instrumental in keeping me sane and grounded. Dr. Lauren Szczygiel, Dr. Ed Szczygiel, Dmitri Barvinok, Charlotte Grenier- Barvinok, Jon Roney, Andy White, and Carly Schneider, thank you for making me feel like a part of your family and for feeding me with your friendship as much as your food. Dr. Maeve Daly, Nick Kanillopoolos, Mallory Newsted, and Nora Wixom, thank you for your love and support throughout the many different seasons of our lives.