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The Study of Animal Bones

Page history last edited by Tess Barrett 9 years ago

 

Bones, remnants of the vertebrate animals are perhaps the most common and ubiquitous finds recovered on archaeological sites. Unfortunately there have been and still are times when this component of the archaeological evidence has not been collected, but discarded as being of little importance. My personal attitude is that anything remaining from the activities of ancient man is important to his study, and since often the remnants of his hunting, pastoral and manufacturing activities are so abundant, their study will inevitably produce conclusions of value to the study of past societies. The study of bones found in archaeological sites is an extension of the paleontological study of Pleistocene fossils, often associated with Paleolithic man, to those remains grouped with more recent cultures in post-glacial times. They have been studied with varying degrees of intensity for more than a century, the work generally being concentrated upon the prehistoric periods, often in company with the study of early agriculture and the pastoral activities of man. More importance is being attached and more work carried out in this field today as archaeologists are converted from the ‘treasure hunting’ of the past to the more responsible research into the lives of our ancestors.

 

Bone itself is composed of an organic and inorganic fraction and although in some cases the organic fraction (collagen, which is resistant to decay) is completely broken down and leached out, it is rarely the case that the inorganic fraction (Calcium phosphates and carbonates) is destroyed except under very acid conditions or due to extreme erosion. This means that on most archaeological sites the majority if not all the bone is preserved in a recognisable and identifiable state.

 

The vertebrate skeleton consists of a number of paired (appendicular) and medial (axial) elements which within each class of animals (fish, amphibian, reptiles, birds and mammals), show a remarkable uniformity of basic design, varying to a greater or lesser extent dependent upon the function of the bone. Rarely are these characters masked by adaptive changes to the extent that the bone is unrecognisable and it is therefore possible to identify all complete bones and a large proportion of the fragmented bones as to element. This is the first stage in the treatment of animal bone, since no attempt can be able to identify the species of the specimen without first establishing the bone type.

 

The five classes of animal mentioned above may generally be fairly readily separated upon either the structure or design of the bones. Bird bones are very thin walled with large (pneumatic) cavities that in life are filled with air and lighten the animal; fish bones tend to be very transparent except when stained and have a polished appearance and no cancellous tissue (the spongy bone found within the ends of the long bones and other parts of the skeleton).

 

Having established the class of animal and the identity of the bone to which the specimen belongs, it is then necessary, by use of known comparative material, to identify its species. The majority of bones on archaeological sites are mammalian and generally domestic, except on the earlier prehistoric sites. Although the basic design of the bones in any one class is similar, the changes in function of the bones produces variations in adaptive design resulting in recognisable features by which the bones can be distinguished as to species: these variations will depend upon whether the animal (in mammals) is a long legged grazer which needs to be fast on its feet over long distances to escape predators, or a carnivore which actively hunts by springing on animals and running them down over short distances, a mole which burrows vigorously though the earth, and so on. Some closely related species are so similar that a species identification is not possible for many of the bones of the body and in some cases skulls are often the only certain method of separating the species; this is true of sheep and goats, and also of numbers of the small mammal species of mice, voles and shrews.

 

Animals grow continually until they reach maturity, and it is necessary that their bones can also grow in size. At either end of the major long bones of the skeleton, a layer of cartilage separates the ends (epiphyses) from the shaft and forms growth points where the bone increases in length until the definitive size is reached; at this time the cartilage becomes ossified (turned to bone) and growth is then complete. This fusion at the ends does not occur at the same age for all bones, some fusing before others. In archaeological deposits, the bones from young individuals lose their ends and depending upon the bone represented, it is possible to estimate the age of the animal from which it was derived. Also, the age at which certain teeth erupt is known in modern animals and the eruption and wear of the teeth recovered can also be used to age specimens.

 

A further piece of information which can be gathered from some bones and teeth is the sex of the animal. The presence of a spur on the tarso-metatarsus of a fowl, indicates that the bird was a cock; the very large canines of the boar can be distinguished from those of the sow, and in some other animals such as cattle, the cows and bulls can be separated on the basis of the proportions of the skull. There is another method of establishing the sex of the animals from which a bone is derived and the presence of any castrated animals: this is done by a metrical analysis and can only be carried out when sufficient numbers of certain bones have been recovered. Some of the bones of the skeleton vary in proportions between the sexes all the collection of a single measurement from a number of bones (or an index of two measurements) when plotted graphically or in the form of a histogram will produce two peaks if both the sexes are present, and some times three if a percentage of the animals are castrated.

 

The above discussion outlines the information that can be gathered concerning the type and condition of the animals usually represented on an archaeological site. This, in conjunction with further features, can now be used to demonstrate man's control and use of them, thus giving an insight into their former importance

 

The extent to which the information gathered can be used in an interpretative way is largely dependent upon the situation and type of site from which the material was recovered. The complete excavation of a Bronze Age village, for example, gives an insight into the major domestic species, their mode of husbandry, the significance of hunting and the relative economic importance of the various species. But a collection from an excavation of a more limited area, for example a single tenement spanning only some three hundred years in the centre of Viking York, may represent only part of the dietary remains of four or so generations of a single family who would probably have bought their meat from the butcher. In this case no reliable information on availability, animal husbandry or even economic use, apart from diet, can be concluded, since the bones may reflect personal vagaries rather than aspects of the community as a whole; in other words, it may represent a biased sample, and there is no way of telling this without reference to other sites in the vicinity.

 

However, if the whole city is treated as a single archaeological site and the various excavations as individual social units, the potential is immense. The results from any one site can only be assessed when material from a number can be used for comparison, and only then can the similarities and differences be used to identify the effects of arisen husbandry, social and economic factors.

 

Interpretation of the material is based upon the secondary use of the information gathered direct from the bones themselves. The species of animals represented can be listed in the proportions in which they have been recovered. This allows consideration of which animals were most important to the community and the extent to which each was either available or utilised. The minimum number of individuals of each species can then be calculated from the most common single skeletal element represented. This figure can be used in some cases to calculate the amount of meat represented: modern estimates of dressed carcass weights are used to calculate how much meat the bones indicate and it is often found that the dietary importance of animals is substantially different from their relative occurrence in the deposits. For instance, cattle are considered as having approximately ten times the weight of sheep when dressed and this would mean that sheep would have to be ten times more abundant than cattle to represent an equality in dietary importance. If the sex characters of the group can now be calculated either by metrical or morphological methods, and the age proportions estimated, an indication of the selection of animals for butchering can be gathered which in turn indicates which groups were most valued alive, and some conclusion drawn as to why. This is important where animals have a number of economic uses: for example, sheep may be priced for wool, milk food and breeding, while cattle may provide draught, milk, hide and food. Some indications of these various uses may be preserved in the skeletal material, notably an oxen used for draught, where the increased loading on the shoulders sometimes regards an enlargement of the metacarpal boned to spread the stress more widely.

 

This approach, as has already been noted, cannot be used for individual sites in York, since economic or even racial and religious factors may govern the selection of meat. But animal remains other than from food ate found on sites and these are particularly interesting from an archaeological point of view. A recent watching brief under the new Habitat shop in Coppergate (INTERIM Issue 2-2 ) produced a small group of bones 20% of which were tines, parts of tines and parts of the beam of red deer antlers. There were no other red deer bones in the whole group, possibly suggesting that the meat itself was hard to come by or too expensive. The antler was presumably being brought in for manufacturing purposes to make a number of objects, none of which were recovered, and only the off cuts and unwanted fragments were found. Associated with these were also a number of sawn horn cores, although there was an absence of any significant neither of other parts of the skull, suggesting that horn was also being utilised for manufacturing purposes either in the some workshop or nearby.

 

Another minor site in York on Leadmill Lane (INTERIM vol 1 no 2) also produced an interesting group from a rubbish pit. Besides incorporating some food debris, the pit contained an unusually large number of ungulate rib fragments, a number of which had been split and smoothed, and also large quantities of very small fragments and shavings of antler. Several fragments from bone comb cases were found associated with this group and it is evident that the antler fragments were derived from the manufacture of the combs themselves.

 

Although successful treatment of individual urban sites is at present only possible in cases where these show manufacturing activities as in the two examples above, it is anticipated that consideration of a number of sites in York within each period will produce information on general agricultural economics as well as the social and economic status of each individual site. One aspect of the long-term study of this material that extends beyond the immediate interests of the archaeologists is the opportunity it creates for the study of the evolution and selection of man's domestic animals, and his effect upon the wild fauna over the last 2000 years, the period during which the most intensive selection and the greatest changes have occurred.

 

One final and interesting aspect of the study of animal bones in archaeology is the insight we get into the history of our wild vertebrate fauna. This country is populated by a large number of species of wild animals so many of which are found in archaeological deposits if assiduously searched for. These animals, be they mammals, birds, etc., are commonly found nowadays in particular habitats such as marsh, heath or woodland, or may even have more specific preferences as to the type of woodland etc., and finds of these species in archaeological contexts can be used for environmental interpretation in conjunction with the botanical and entomological work carried out on site. This is illustrated by finds from the Roman sewer in Church Street, York (INTERIM vol 1 no 1: INTERIM Issue 2-1 ) where a number of small mammal species and other vertebrate animals were recovered, among them, House, Wood, Harvest Mouse, Short-tailed vole and Water vole, Common Shrew and Pygmy Shrew and a mole, a variety that suggests areas of local grassland and low shrub such as that now associated with hedgerows or railway embankments.

There finds give us interesting and early records of our modern fauna and can be used to illustrate the extent and abundance of these species in former times. This is particularly important where a number of our now extinct or recently introduced vertebrates are concerned, notably species such as the wolf, wild boar and beaver, all of which became extinct in the Medieval or Post-Medieval periods, and fallow deer, rabbit, black rat and house mouse, the last being introduced at least by the Iron Age and the fallow deer, rabbit and black rat in the Norman period. It is a recent find in York which suggests that the latter species was a Roman introduction into this country and this day well prove to be a find of some economic and historical importance, the black rat being the carrier of the bubonic plague vector.

 

The scope of the studies illustrate that they can and I hope will prove a valuable and necessary addition to the present archaeological evidence from the city of York, enabling a deeper investigation into the development of the city and its social, economic and environmental conditions.

 

James Rackham

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