The Archaeology of Animal Bones

Terry O'Connor

• Publisher: The History Press
• Year: 2004
• Print ISBN: 9780750935241
• eBook ISBN: 9780752495224
• Topic: Social Sciences
• Subtopic: Cultural & Social Anthropology
• Index: Social Sciences

Animal bones are one of the most abundant types of evidence found in archaeological sites dating from pre-historic times to the Middle Ages, and they can reveal a startling amount about the economy and way of life of people in the past.

This is a fascinating introduction for anyone seeking to understand how these bones can shed light on our knowledge of the past, as well as the complex relationship between human and animals. Written by one of the most respected experts in this field, and published for the first time in paperback, this book will be essential reading for archaeologists, or indeed anyone intrigued by the recreation of long lost worlds from the most insignificant-seeming fragments of animal bones.

ONE

WHY STUDY A LOT OF OLD BONES ?

On reflection, this book has its origins in a basement room at the National Museum of Wales, in Cardiff, over twenty years ago. Even by the standards of academic publishing, twenty years may seem a long gestation, so perhaps I should explain.

Among the clutter in that basement room was a series of boxes containing bones collected during recent excavations at a Roman site called Caerleon. As an impoverished graduate student, I had been offered hard currency in return for studying and recording those bones. Identifying and recording archaeological bones requires a good knowledge of the skeletal anatomy of a wide range of animals, and I had been fortunate enough to have studied with I.W. Cornwall, a particularly influential figure in the development of archaeological bone studies, who taught comparative skeletal anatomy with assurance and skill. The archaeological study of bones also requires a questioning approach, in order to see the significance of small details of anatomy or preservation that might reveal something about the original animals, their involvement with people, and the circumstances of their disposal and burial. My doctoral supervisor was Don Brothwell, well known on both sides of the Atlantic for seeing the important questions before anyone else, and for not accepting received wisdom.

As for the site itself, Caerleon today is an overgrown village close to the town of Newport, in south-east Wales. By the end of the first century ad Caerleon was a booming garrison town serving as a legionary fortress and base for the subjugation of those Welsh tribes who were reluctant to embrace the benefits of Roman civilization. One of those benefits was regular bathing, and the excavations in question had investigated parts of the bath-house and adjacent swimming pool (natatio: excavators of Roman sites have a curious aversion to English). Most of the bones had been recovered during the excavation of the natatio and other bath structures. Having been constructed on a grand scale, the baths were substantially altered in the late third and fourth centuries. The opportunity was obviously taken to dump garbage into the back-filling, and that garbage included a lot of bones.

Another source of numerous bones was that other icon of Romanization, the drains. Baths need drains, and the assorted civilian administrators and off-duty grunts who used the baths occasionally dropped things into the drains, including coins, items of personal adornment, and the bones from light snacks consumed while enjoying the facilities. The Caerleon bones thus offered a real opportunity to investigate both the general garbage of the fortress and the particular leavings of the bath-house clientele.

And so it proved. Deposits in the natatio back-fill and other garbage accumulations around the bath-house complex contained mostly cattle bones, but not just any cattle bones. Some deposits had a preponderance of head and foot bones, arguably the debris from the first stages of slaughter and butchering. Others contained a high proportion of shoulder blades, indicating a pattern of butchery unlike that commonly seen today. Years later, I was to encounter heaps of Roman cattle shoulder blades again, this time in York, another garrison town. By an analysis of body-part distribution for the Caerleon cattle, it was possible to piece together something of the butchering procedure in use at the time, and to suggest that butchering and the disposal of refuse from it became rather less systematic as the civilian influence on life in the fortress increased.

The drains told a different story. Here there were very few cattle bones. Instead, the bones were mostly sheep ribs and vertebrae, and chicken bones. The bath-house catering came to life: pieces of chicken and lamb chops. This must have been a welcome contrast to the unremitting beef indicated by deposits elsewhere on the site.

And there was more. In one of the bath-house buildings, the frigidarium, the last surviving floor of Roman date was overlain by a patchy light brown deposit that consisted almost entirely of small bones. There were so many small bones, in fact, that it would have been quite impossible to record each of them individually, forcing me to take decisions about sampling. In the end, I sorted a small sub-sample by body part – a pile of tiny mandibles, a heap of minute shoulder blades – then identified all the skulls and mandibles as precisely as possible. Most proved to be species of rodent, with some shrews, and a few frogs. After the piles of butchered cattle bones, the intellectual challenge of identifying field voles and water shrews was totally absorbing, and so-called ‘small mammals’ have remained a particular interest. Venturing out of the basement to the elevated marble halls of the Museum one day, I mentioned to the eminent Roman archaeologist George Boon that I had found bones of dormouse. ‘The Romans ate dormice, you know,’ he observed, and returned to his scrutiny of some particularly enthralling denarii. Having grown up at the seaside, I have eaten some fairly improbable things, but surely dormice have more to do with Alice and the Mad Hatter? Some hasty research revealed that the reference to dormice in Roman cookbooks was probably to a much larger southern European relative of the species whose tiny bones I had recognized in the frigidarium deposit. However, like the cattle scapulae, Roman dormice were to haunt my subsequent career, and they make a return appearance in Chapter 5.

So why was the frigidarium apparently carpeted with piles of tiny bones? Common sense, that most unscientific of things, ruled out deliberate human activity. Even though we zooarchaeologists accumulate the skeletons of assorted animals in our laboratories and homes (yes, I’m afraid we do), we rarely if ever accept that people in the remote past might have collected skeletons entirely out of interest. Besides, the frigidarium assemblage represented tens of thousands of individual animals, and nobody needs that many mice. Fortunately, a plausible answer lay in the zoological literature. Many other predators accumulate bones at locations to which they have taken prey in order to eat it. Hyenas are particularly adept at this, though they were clearly not responsible for the Caerleon assemblage. In fact, the range of species in the assemblage nicely matched the prey typical of owls, probably barn owls. These superb nocturnal hunters swallow their furry prey in large lumps, then retire to some favourite perch at which to digest the meal. In due course, a pellet of indigestible bones and fur is regurgitated. Where owls repeatedly use the same perch, many pellets will accumulate, leaving a deposit of many tiny bones. The sheer quantity of bones in the frigidarium indicated many owl-years of occupation. That in turn suggested that the building was particularly attractive to owls, a conclusion which in turn fitted neatly with other evidence that the frigidarium had remained standing, with roof intact, for many years after its abandonment. The patient identification of minute bones led back to deductions about the survival of a Roman building in subsequent centuries (see Chapter 11).

By the time I had finished with Caerleon, written the report (O’Connor 1986b), and delivered a conference paper on it, many of the themes that are explained and explored in this book had come together. The deceptively simple process of identifying bones (Chapter 5) was made clear to me by the mice and voles: the skulls and teeth could mostly be identified to species level, the pelvic girdles to genus, the limb bones only to family, and the ribs and vertebrae hardly even to Order. Just understanding the accumulation of the bones had led to the literature on bone taphonomy (Chapter 3). The natatio fills taught a lesson about the information that body-part analysis can reveal (Chapter 7), and my attempts to express the quantities of cattle bones in numbers brought quantification methods to the fore (Chapter 6). Measurement of some of the more complete bones had given an estimate of the stature of the cattle, and measurements of mouse mandibles had helped to separate two closely related species (Chapter 10). Most of all, when unusual or abnormal specimens had me puzzled, a stroll up the road to Cardiff’s University College brought me to the cactus-infested office of Barbara Noddle, who would dispense osteological wisdom with precision, humour, and a rare talent for oblique digression.

Presenting Caerleon as the source of much that follows in this book is, of course, a plot device, a useful hook on which to hang a sometimes highly technical text. However, in the intervening couple of decades, I have studied many (too many!) other bone assemblages, large and small. Some have been a serious challenge in practical terms, while others have led to unexpected deductions. None, I think, has stimulated the critical faculties in quite the way that the Caerleon bones did. While assembling material for this book, I disturbed my Caerleon records from their eternal rest, and soon lost myself in one of those ‘That’s interesting, I wonder if …’ moments. Pieces of ancient bone lack the aesthetic appeal of artefacts or the grandeur of ancient buildings, yet they have a complex fascination that arises in part from their zoological origin, as evidence of long-dead animals, and in part from what we can infer from them about past human activities, and about the involvement of people in those animals’ lives.

Of necessity, parts of this book are quite technical in their content, requiring patience, if not stamina, of the reader. I think that is unavoidable. In order to understand the potential of archaeological bone studies, we have to understand bone itself, and what can have happened to it before we lift it on to the laboratory bench. Each of the various analytical procedures that we use has some basis in zoology or statistics, and we need to understand that background if we are to use the methods intelligently. The process of interpretation and deduction merits examination, too, with discussion of what we have inferred from animal bone assemblages about our diverse and changing relationship with our helpers, vermin, pets and dinners.

The author’s first language is English, and most of the examples cited here are from the English language, though not necessarily British literature. The emphasis given to certain issues, and the sometimes idiosyncratic choice of illustrative examples, reflects my own interests and those published works that have caught my attention, or that of my students. The aim has been to produce a book that introduces the study of ancient animal bones in some depth, and provides enough sources to allow the enthusiastic reader to pursue the detail. At the same time, the text should be read as an explanation of why animal bones are fascinating, deserving of study, and an important source of information about what people did in the past.

TWO

BONE, BONES AND SKELETONS

Part of the fascination of working with ancient bones is that they are parts of formerly living animals. Unlike potsherds or stone tools, bones have been alive, and their complexity reflects that origin. We need to understand the constituents of bone, and how they are organized, in order to understand how, and whether, bones will survive burial and excavation. Furthermore, we need to understand the basic structure of the vertebrate skeleton if we are to comprehend those excavated fragments as parts of whole animals. The purpose of this chapter is to introduce bone as a tissue, and to outline the structure of the vertebrate skeleton. There is a lot of anatomical terminology in this chapter: subsequent chapters use precise anatomical terms where necessary, and this is the place where they are introduced. Readers who are less concerned with the osteological details, or who find it all too much, may prefer to skip to the summary of this chapter before reading on, and then to return to this chapter as a source of reference as necessary.

BONE COMPOSITION

Bone is a living tissue with cells and a blood supply, just like muscle or skin. As an animal grows, so its bones grow and undergo modification and repair. Thus the form of the skeleton at the time of death is one point in a process of continuous change. By the time archaeologists deal with the bone, it is a hard, dead material, much altered since the animal’s death. It is important to remember that bone in the living animal is as susceptible to damage or alteration as any other living tissue. An excellent introduction to bone, and especially to its versatility as a skeletal material, is given by Alexander (1994), and Halstead (1974) remains a useful source.

Fresh bone has three main components: a complex protein scaffolding; a mineral which stiffens this scaffold; and a ‘ground substance’ of other organic compounds. Although proportions vary in different tissues, about half of the weight of fresh bone is mineral, the remainder being organic matter and water.

Of the organic fraction, about 95 per cent is the structural protein collagen (Miller & Gay 1982; Linsenmayer 1991), which is unusual in containing high proportions of the amino acids glycine and hydroxyproline. Collagen molecules have few large side-chains and can pack together very closely, bonding at regular intervals. The macromolecules are arranged in a left-handedly spiralling triple helix, which itself spirals to the right about a central axis. The structure is a bit like a traditional hawser-laid rope, and gives collagen its characteristics of being strong under tension yet flexible.

The mineral phase is mainly hydroxyapatite. This may be loosely described by the formula Ca₁₀(PO₄)₆.(OH)₂, though the Ca ions may be replaced by Sr, Ra, or Pb, the PO₄ions by CO₃, and the OH groups by F. Other ions, mostly metals, can be attached to the surface of hydroxyapatite crystals by adsorption, which may occur in living bone, but can also occur in dead, buried bone (Lee-Thorp & van der Merwe 1981; Millard & Hedges 1995). It can therefore be difficult to tell whether the chemistry of an ancient bone reflects its chemistry during life, or the burial environment after death.

The ground substance makes up only a very small proportion of fresh bone. It serves as a packing, and probably also regulates hydration, and is composed of a mixture of mucoproteins and aminopolysaccharides.

BONE STRUCTU...

Table of contents

• Cover
• Title
• Dedication
• Contents
• Preface
• 1 Why Study a Lot of Old Bones?
• 2 Bone, Bones and Skeletons
• 3 Taphonomy: From Life to Death and Beyond
• 4 Excavation and Recovery
• 5 Identification and Description
• 6 Counting Bones and Quantifying Taxa
• 7 Out on a Limb: Body-Part Quantification
• 8 Estimation of Age at Death
• 9 Palaeopathology: Understanding Sickness and Injury
• 10 Metrical and Non-Metrical Variation
• 11 Climate, Environment and Small Vertebrates
• 12 Hunting and Fishing: People as Predators
• 13 Settling Down: The Domestication of Animals and People
• 14 Urban Garbage: On Drovers, Butchers, Wealth and Rats
• 15 More Than Just Old Bones
• Bibliography