A Biometric Study of Equids in the Roman World Cluny Jane Johnstone
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A Biometric Study of Equids in the Roman World Cluny Jane Johnstone Thesis submitted for PhD University of York Department of Archaeology September 2004 1 2 Abstract Arguably horses and their close relatives have been amongst the most important domestic mammals in the history of human development. Equids have provided benefits to humankind that other domestic mammals were unable to offer: – specifically their ability to be trained and ridden. Equids were particularly crucial to the expansion and success of the Roman Empire. The equids studied for this thesis were the horse (Equus caballus), the donkey (Equus asinus) and their hybrid the mule (male donkey x female horse). The first major area of research focused on the discrimination of the bones of these equids. A new methodology, using discriminant function analysis on biometric data, was developed to enable the positive identification of these equids. This methodology was then applied to a large set of archaeological data to determine whether there was a real discrepancy in species proportions between the contemporaneous literature and the zooarchaeological record. It was discovered that the hitherto perceived difference was caused by identification problems and that mules were ubiquitous across the Empire. Withers height estimations, shape index and log ratio calculations were carried out on the identified equid material to look at differences between various groups of data. It was established that Roman conquest had an effect on the physical appearance of horses in the Empire. This effect varied considerably and although improvements in size were universal the appearance of the Roman horses was found to vary according to the differences in the preceding Iron Age stock, corroborating the contemporaneous literature and art historical sources. It was also determined that the trade of, and use of, equids was evident from the presence of mules and donkeys in areas external to, but contemporaneous with, the Empire. This study shows the potential of a synthetic biometric survey of a single family of animals, within geographic and temporal limits, once the problem of identification has been overcome. 3 4 Contents Abstract ............................................................................................................................. 3 List of figures ...................................................................................................................... 8 List of Tables .................................................................................................................... 12 List of Appendix figures .................................................................................................... 16 List of Appendix tables ..................................................................................................... 17 Acknowledgements .......................................................................................................... 18 Author’s Declaration ......................................................................................................... 18 Chapter One – Introduction .......................................................................................... 19 1.1 Subject to be addressed ............................................................................................. 19 1.2 Introduction to current research themes in studies of the Roman world ......................... 23 1.2.1 Romanisation ...................................................................................................... 24 1.2.2 Regionality .......................................................................................................... 25 1.2.3 Frontiers ............................................................................................................. 27 1.2.4 External contact .................................................................................................. 29 1.2.5 Trade and supply ................................................................................................ 30 1.2.6 Roman / post-Roman transition ........................................................................... 34 1.3 Roman equids in art and literature ................................................................................ 35 1.3.1 Horses ................................................................................................................ 38 1.3.2 Mules ................................................................................................................. 65 1.3.3 Donkeys ............................................................................................................. 68 1.4 Roman equids in archaeology and zooarchaeology ....................................................... 71 1.4.1 Mules and donkeys ............................................................................................. 72 1.4.2 Horses ................................................................................................................ 73 1.5 Terminology ................................................................................................................ 88 1.5.1 Breeds and demes .............................................................................................. 88 1.5.2 Appearance and conformation ............................................................................. 89 1.5.3 Taxonomic nomenclature ..................................................................................... 90 1.5.4 Use of the term species ....................................................................................... 92 1.5.5 The measurement unit hands ................................................................................ 92 1.5.6 Use of the terms Iron Age, Roman and External ................................................... 93 1.6 How the subject is to be addressed ............................................................................. 94 Chapter Two – Bone and skeletal biology .................................................................... 95 2.1 Introduction ................................................................................................................ 95 2.2 What is bone? ............................................................................................................ 95 2.3 Bone growth under ideal conditions ........................................................................... 102 2.4 Factors affecting bone growth ................................................................................... 106 2.4.1 Age .................................................................................................................. 106 2.4.2 Sex ................................................................................................................... 111 2.4.3 Nutrition ........................................................................................................... 115 2.4.4 Hormones ......................................................................................................... 121 2.4.5 Genetic potential ............................................................................................... 123 2.4.6 Exercise ............................................................................................................ 125 2.4.7 Disease and pathology ...................................................................................... 126 Chapter Three – Methodology ................................................................................... 137 3.1 Measurement choice and collection ........................................................................... 137 3.1.1 Measurement choice ......................................................................................... 137 3.1.2 Data collection .................................................................................................. 142 5 3.2 Database construction and structure .......................................................................... 142 3.3 Analytical techniques and statistics ............................................................................. 146 3.3.1 Log-ratio technique ........................................................................................... 146 3.3.2 Student’s t-tests ................................................................................................ 148 3.3.3 Discriminant function analysis ............................................................................. 149 3.3.4 Withers height calculations ................................................................................. 150 3.4 Critical evaluation of withers height calculation methods ............................................. 151 3.5 Summary .................................................................................................................. 161 Chapter 4 - Critical evaluation of methods of species separation ............................. 163 4.1 Dental morphology ................................................................................................... 163 4.2 Dental biometry ........................................................................................................ 167 4.3 Bone morphology ..................................................................................................... 170 4.3.1 Cranial morphology ........................................................................................... 171 4.3.2 Post-cranial