Establishing a Methodology for Determining Handedness in Lithic Materials As a Proxy for Cognitive Evolution
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EXPERIMENTAL ARCHAEOLOGY AND HOMINID EVOLUTION: ESTABLISHING A METHODOLOGY FOR DETERMINING HANDEDNESS IN LITHIC MATERIALS AS A PROXY FOR COGNITIVE EVOLUTION by Lana Ruck A Thesis Submitted to the Faculty of The Dorothy F. Schmidt College of Arts and Letters In Partial Fulfillment of the Requirements for the Degree of Master of Arts Florida Atlantic University Boca Raton, FL December 2014 Copyright 2014 by Lana Ruck ii ACKNOWLEDGEMENTS I would like to thank my thesis committee members, Dr. Douglas Broadfield, Dr. Clifford Brown, and Dr. Kate Detwiler, for their constant support and help with developing this project, as well as the head of the Department of Anthropology, Dr. Michael Harris, for his insights. This project would not have been possible without the help of my volunteer flintknappers: Ralph Conrad, Mike Cook, Scott Hartsel, Ed Moser, and Owen Sims, and my raw materials suppliers: Curtis Smith and Elliot Collins. I would also like to thank Miki Matrullo and Katherine Sloate for cataloging my handaxes and flakes and aiding me in creating a blind study. Special thanks to Justin Colón and Dr. Clifford Brown for assessing a random sample of my flakes, adding objectivity to this study. Finally, I would like to thank Dr. Natalie Uomini for her constant help and support of my project. iv ABSTRACT Author: Lana Ruck Title: Experimental Archaeology and Hominid Evolution: Establishing a Methodology for Determining Handedness in Lithic Materials as a Proxy for Cognitive Evolution Institution: Florida Atlantic University Thesis Advisor: Dr. Douglas Broadfield Degree: Master of Arts Year: 2014 Human handedness is likely related to brain lateralization and major cognitive innovations in human evolution. Identifying handedness in the archaeological record is, therefore, an important step in understanding our cognitive evolution. This thesis reports on experiments in identifying knapper handedness in lithic debitage. I conducted a blind study on flakes (n=631) from Acheulean handaxes replicated by right- and left-handed flintknappers. Several flake characteristics significantly indicated handedness, with a binary logistic regression correctly predicting handedness for 71.7% of the flakes. However, other characteristics were not associated with handedness. This is a result of personal knapping styles, as additional analyses show that individual knappers associate with some attributes better than handedness does. Continued work on these methodologies will enable analysis of Paleolithic assemblages in the future, with the v ultimate goal of tracking population-level hominid handedness rates through time and using them as a proxy for cognitive evolution and language acquisition. vi DEDICATION To my closest friends and family, who now know more about handedness than they ever cared to. Thanks for putting up with me every day. EXPERIMENTAL ARCHAEOLOGY AND HOMINID EVOLUTION: ESTABLISHING A METHODOLOGY FOR DETERMINING HANDEDNESS IN LITHIC MATERIALS AS A PROXY FOR COGNITIVE EVOLUTION LIST OF TABLES .............................................................................................................. x LIST OF FIGURES .......................................................................................................... xii INTRODUCTION .............................................................................................................. 1 History of “Handedness” ................................................................................................. 1 Brain Complexity: Hemispheric Specialization and Lateralization ................................ 3 Issues in Studying Human Asymmetries ........................................................................ 4 Lithic Analysis and the Value of Paleolithic Technology ............................................... 6 Experimental Archaeology .............................................................................................. 7 PREVIOUS RESEARCH ................................................................................................. 10 Living Humans: Asymmetries in the Body and Brain .................................................. 10 Non-human Primates: Is Handedness an Autapomorphy? ............................................ 15 The Hominid Fossil Record: Direct and Indirect Evidence for Handedness ................ 18 METHODS ....................................................................................................................... 30 Creation and Collection of Materials ............................................................................ 30 Preliminary Lithic Cataloging and Analysis ................................................................. 32 Identification of Handedness-Indicative Features—Toth and Rugg and Mullane ........ 35 Identification of Handedness-Indicative Features—Bargalló and Mosquera ............... 38 Reconstruction of Assemblages and Statistical Methods .............................................. 41 RESULTS ......................................................................................................................... 45 Assessment of Toth’s and Rugg and Mullane’s Methods ............................................. 45 Assessment of Bargalló and Mosquera’s Methods—non-statistical measures. ............ 48 Binary Logistic Regression—which traits predict handedness? ................................... 52 Additional Analysis—Effects of Knapping Style on Flake Debitage ........................... 74 viii Inter-observer Comparisons—Assessment of Bargalló and Mosquera’s method’s reliability ................................................................................................................ 78 CONCLUSIONS............................................................................................................... 85 Synthesis of Results for the Toth, Rugg and Mullane, and Bargalló and Mosquera methodologies ........................................................................................................ 85 Additional Considerations and Recommendations ....................................................... 89 Implications of this Study: Applying Experimental Data to Fossil Assemblages ........ 94 Cognitive Evolution and Language Acquisition ........................................................... 96 APPENDICES .................................................................................................................. 97 A—Subset Handedness Inferences by Handaxe ........................................................... 98 B—Overall Frequency Data for Technical Features ................................................... 100 C—Binary Logistic Regression Case Processing Summaries .................................... 103 D—Technical Features Frequency Data by Handedness ............................................ 104 E—Technical Features Frequency Data by Knapper .................................................. 108 F—Overall Frequency Data for Technical Features: Observer B ............................... 115 G—Overall Frequency Data for Technical Features: Observer C .............................. 118 H—IRB Approval ....................................................................................................... 121 REFERENCES ............................................................................................................... 122 ix LIST OF TABLES Table 1: Summary of classification sets and their associated types ................................. 38 Table 2: Meta-assemblage breakdown by handaxe and knapper ...................................... 42 Table 3: Summary of the Toth (1985) cortex-based method ............................................ 46 Table 4: Summary of the Rugg and Mullane (2001) cone of percussion method ............ 48 Table 5: Evaluation of overall handedness inferences by handaxe .................................. 49 Table 6: Binary logistic regression values for the cone of percussion subset.. ................ 56 Table 7: Measures of significance for the cone of percussion regression ........................ 56 Table 8: Summary of predictive correctness for the cone of percussion regression subset..................................................................................................................... 58 Table 9: Binary logistic regression values for the eraillure scar subset. ........................... 59 Table 10: Measures of significance for the eraillure scar regression ................................ 59 Table 11: Summary of predictive correctness for the eraillure scar regression subset..................................................................................................................... 59 Table 12: Binary logistic regression values for the platform subset. ................................ 60 Table 13: Measures of significance for the platform regression....................................... 60 Table 14: Summary of predictive correctness for the platform regression subset ............ 61 Table 15: Binary logistic regression values for the cortex subset. ................................... 62 Table 16: Measures of significance for the cortex regression .......................................... 62 Table 17: Summary of predictive correctness for the cortex regression subset ............... 63 Table 18: Binary logistic regression values for the fracture location subset. ................... 64 Table 19: Measures of significance for the fracture location regression .........................