SEXUAL DIMORPHISM OF THE ILIUM AND ILIAC CREST: A QUANTITATIVE APPROACH A Thesis by Joy H. Vetter B.S., Kansas State University, 2006 Submitted to the Department of Anthropology and the faculty of the Graduate School of Wichita State University in partial fulfillment of the requirements for the degree of Master of Arts May 2009 © Copyright 2009 by Joy H. Vetter All Rights Reserved SEXUAL DIMORPHISM OF THE ILIUM AND ILIAC CREST: A QUANTITATIVE APPROACH The following faculty members have examined the final copy of this thesis for form and content, and recommend that it be accepted in partial fulfillment of the requirement for the Degree of Master of Arts with a major in Anthropology Peer H. Moore-Jansen, Committee Chair Robert Lawless, Committee Member John Gries, Committee Member iii ACKNOWLEDGMENTS I would like to thank the Nancy Berner Research Fund for providing generous support to cover travel expenses for my research on the Hamann-Todd osteological collection. I am indebted to the Cleveland Museum of Natural History for allowing me access to the Hamann- Todd collection and Lyman Jellema for his assistance during my stay in Cleveland. Special thanks must be given to my adviser, committee chair, mentor, and friend, Dr. Peer H. Moore-Jansen. His patience, guidance, and support over the last several years have allowed me to grow as a person and as an anthropologist. The seemingly impossible challenges and opportunities that he has provided for me were truly invaluable in my growth as an osteologist. The completion of this degree would have been unattainable without his guidance and patience. I can’t thank you enough Peer. I still owe you a bottle of juice. I would like to thank my committee members Dr. Lawless and Dr. Gries. I know that it is time and energy consuming to serve as a committee member. Your input, support, and patience were greatly appreciated. Throughout the last three years I was fortunate enough to meet, study with, and learn from a group of very special and talented anthropologists. All of their encouragement, understanding, advice, and friendship made navigating graduate school fun and interesting. Thank you Angie Rabie, Julie Holt, Kristen Bernard, Laura Bennett, and Evan Muzzall. You all hold a very special place in my heart and I am forever grateful for your friendship. I would also like to thank my parents, sisters, and family. A lifetime of unconditional love, guidance, and support has shaped me into the person that I am today. Thank you for iv allowing me the freedom and space to grow. I cannot put into words how much I love and appreciate all of you. Last, but certainly not least, a special thanks must be given to the love of my life, Tarl. For the last several years he has unselfishly put all of his effort into supporting me so I could achieve my dreams. He has had to endure my late nights, grumpy days, and long hours and did so graciously. I admire his uncanny ability to love me in my “finest” moments. Tarl provided much needed assistance in several tangible ways such as helping me with all of the vector calculus, trigonometric functions, Excel spreadsheets, and editing and in numerous non-tangible ways including encouragement, patience, support, and unconditional love. More importantly, Tarl has helped me realize my true potential. He is my inspiration and saving grace. Words cannot describe how much I appreciate all that he has done for me. Tarl, I could not have done it without you. v ABSTRACT This study examined indicators of male-female differences in the os Coxa, specifically in the shape of the ilium and iliac crest for the purpose of skeletal sex estimation. The iliac crest is a curved, or “S” shaped, epiphysis which extends along the cranial margin of the ilium, posteriorly from the anterior superior iliac spine to the posterior superior iliac spine of the os Coxae. Forty two metric variables characterizing the shape of the os Coxa and iliac crest were derived from a digital database of 150 adult White human os Coxae, including 75 males and 75 females, from the Hamann-Todd osteological collection at the Cleveland Museum of Natural History. The os Coxae were all digitized using a MicroScribe-3DX digitizer, and the data was stored in an excel spreadsheet, which facilitated further mathematical analysis to define and calculate all variables. A single point of origin defined as the most superior point in the midline of the pubic symphysis, was common to each variable. This study hypothesized that these variables will better define variation in form, and that they will better characterize sexual dimorphism in the iliac crest. Thus serve as an aid in sex estimation. Additionally, the qualitative observation of the sciatic notch was compared to the quantitative observations. Statistical analyses, including descriptive statistics, univariate sectioning points, independent t-tests, and proportional analyses, were used to test the potential application of the findings of this study to sex identification in osteological investigation. The results of this research suggested that there were slight indications of sexual dimorphism in several of the iliac blade dimensions along with the central chords of the iliac crest and their associated angles. Despite indications of differences in the female and male form, the measurements proved to be too variable, thus making accuracy and reliability unattainable. Further investigations are required to better understand the presented findings. vi TABLE OF CONTENTS Chapter Page 1. INTRODUCTION…………………………………………………………………. 1 2. BACKGROUND…………………………………………………………………... 4 Introduction………………………………………………………………………… 4 The Adult Pelvic Girdle……………………………………………………………. 5 The Anatomy of the Adult Os Coxa………………………………………………...7 The Adult Ilium……………………………………………………………..7 The Adult Ischium…………………………………………………………. 10 The Adult Pubis……………………………………………………………. 11 Growth and Development of the Os Coxa…………………………………………. 11 Sexual Dimorphism in the Adult Os Coxa………………………………………… 13 Methods of Identification Using the Adult Os Coxa………………………………. 14 Qualitative Analysis of the Adult Os Coxa………………………………… 15 Quantitative Analysis of the Adult Os Coxa………………………………..18 Methods of Identification Using the Iliac Crest……………………………. 23 3. MATERIALS AND METHODS…………………………………………………... 25 Introduction………………………………………………………………………… 25 Materials…………………………………………………………………………… 25 Independent Test Sample…………………………………………………... 26 Hardware…………………………………………………………………………… 27 Software……………………………………………………………………………. 28 Quantitative Observations………………………………………………………….. 28 Qualitative Observations…………………………………………………………… 35 Digital Collection Protocol………………………………………………………… 35 Digitization………………………………………………………………… 35 Exporting Data……………………………………………………………... 37 Importing Data……………………………………………………………... 38 Translating Digital Data into Linear Measurements……………………….. 38 Calculations…………………………………………………………………………40 Analytical Methods………………………………………………………………… 45 4. RESULTS………………………………………………………………………….. 47 Introduction………………………………………………………………………… 47 Descriptive Statistics……………………………………………………………….. 47 Univariate Sectioning Points………………………………………………………..54 vii TABLE OF CONTENTS (continued) Chapter Page Independent t-tests…………………………………………………………………. 58 Proportional Analysis……………………………………………………………….59 Univariate Sectioning Point and Independent t-tests Comparison Analysis………. 60 Univariate Correct Classification for the Sciatic Notch…………………………… 62 5. DISCUSSION……………………………………………………………………… 63 Introduction………………………………………………………………………… 63 Metric Results……………………………………………………………………… 63 Descriptive Statistics……………………………………………………….. 63 Univariate Sectioning Points………………………………………………..64 Independent t-tests…………………………………………………………. 65 Proportional Analysis……………………………………………………….66 Univariate Correct Classification for the Sciatic Notch…………………… 66 Morphological Implications of the Metric Results and Their Relationship to Previous Studies……………………………………………………………………. 67 Summary and Conclusion………………………………………………………….. 69 REFERENCES……………………………………………………………………………..71 APPENDIX… ……………………………………………………………………………....76 Diagrams of Quantitative Observations…………………………………………….77 viii LIST OF TABLES Table Page 1. Definitions for the Iliac, Anterior, and Posterior Breadths, Subtense, Anterior and Posterior Lengths, and the Triangular Areas………………………… 30 2. Definitions of the Seventeen Chords………………………………………………. 31 3. Definitions of the Sixteen Angles………………………………………………….. 33 4. Female Descriptive Statistics for the Calibration Sample (n=75)…………………. 48 5. Male Descriptive Statistics for the Calibration Sample (n=75)……………………. 49 6. Female Descriptive Statistics for the Independent Test Sample (n=17)…………… 52 7. Male Descriptive Statistics for the Independent Test Sample (n=17)……………... 53 8. Univariate Correct Classification Results for the Calibrations Sample……………. 55 9. Univariate Correct Classification Results for the Independent Test Sample………. 56 10. Statistically Significant Variables for the Calibration Sample…………………….. 58 11. Statistically Significant Variables for the Independent Test Sample………………. 59 12. Proportional Analysis Results for the Calibration Sample………………………… 59 13. Proportional Analysis Results for the Independent Test Sample…………………... 60 14. Statistically Significant Variables for the Calibration Sample and Associated Univariate Correct Classification Results……………………………... 61 15. Statistically Significant Variables for the Independent Test Sample and Associated Univariate Correct Classification Results……………………………... 61 LIST OF TABLES (continued) ix Table Page 16.