By Emma-Jayne Evans
A whole range of techniques can be used to gain as much information as possible from the bones. One of the most important aspects of studying animal bones from an archaeological site is to try to determine the animal husbandry techniques that were being used by the site’s inhabitants. This can tell us what they were using their domesticated animals for.
A key factor is the age at which the animals died. It is generally thought that the presence of lots of very young animals, and a number of older individuals, represents an economy based on milk production. Unwanted calves would have been killed at an early age so that the milk could be used for human consumption. If animals are kept primarily for meat production, many of them will be killed at the optimum age for meat yield, just as the animal is fully grown.
There are various ways of identifying age at death, and animal bone specialists will usually record a number of standard observations on assemblages in order to determine this. For example, like human beings, animals have two sets of teeth in their life - their deciduous (milk) teeth, and their permanent adult teeth. We can estimate the ages at which these deciduous and adult teeth erupt in different species, and then use this information to determine the ages of animals found on an archaeological site (see figure 1). During an animal’s life its teeth gradually wear down, forming different wear patterns on each tooth. These patterns can also be used to establish an animal’s age when it died.
Figure 1: Sheep jaw bones (mandibles), showing three different stages of tooth eruption. From left to right, the animals were aged as 3 - 5 years, 20 - 34 months and 10 - 20 months (click on the image to view in more detail).
The bones are another indicator of an animal’s age. All baby animals (including humans) are born with the ends of the limb bones detached from the main shaft, as shown in figure 2. This allows the bone to grow in length, and it is only when the animal is fully grown that the bones finally fuse together. Bone fusion occurs at set ages, and by studying the state of fusion of the bones, we can determine the age at death of an animal.
Figure 2: The bone on the left is an adult, fully fused bone from the fore-leg (a metacarpal), and the bone on the right is the same bone but from a juvenile, showing how the end is unfused to allow the bone to grow in length (click on the image to view in more detail).
Many bones preserve butchery marks, such as dismemberment cut marks around the joints of bones as animals are cut up into joints of meat, and filleting marks where meat is taken off the bone. This evidence can help us to understand how people were processing the carcasses and this in turn can tell us about how animal products were being used. Limb bones, for example, are often chopped open to get at the bone marrow within, a useful source of fat for the diet, for burning as fuel, and for waterproofing skins. A distinctive type of butchery mark can be found on cattle scapulae (shoulder blades) from the Roman period, in which a hole is pierced through the blade (see figure 3 below). It is likely that these holes are caused by hanging the shoulder of meat from a hook for smoking or salting.
Figure 3: This picture shows a cattle shoulder blade (scapula) with a line-shaped hole pierced in the blade where the animal would have been hung up by a hook for salting or smoking (click on the image to view in more detail).
Animal skins were also a valuable commodity, and we look for signs that skinning was taking place. Cut marks are often found on the skull and circling the ends of the lower limbs, where the skin would be detached from the animal and removed in as complete a state as possible. Animals were used for traction as well, to pull carts and ploughs, and it is thought that constant pulling of heavy loads imposed stresses on the animals’ limb bones. This caused the ends of the bones to splay, with extra bone growth around the joints forming to strengthen lower limb joints against the heavy forces (see figure 4 below).
Figure 4: The bone on the left shows the hind-leg bone from a cow (a metatarsal), in which the end articulations have splayed, often thought to be caused by the stresses imposed on the legs during traction. The bone on the right is a normal metatarsal for comparison (click on the image to view in more detail).
Animal bone analysis can also determine which wild animals were exploited by the occupants of an archaeological site, and whether or not these wild animals played an important part in the diet of past populations. The presence of wild animals such as deer, rabbit and hare suggests that these animals were being hunted for their meat and skins, or for sport.
We can also identify species that lived in Britain in the past but are no longer found here, and conversely, species which were introduced here from elsewhere. Beavers and bears, for example, are no longer found in Britain, but they used to be quite common and their remains have been found on numerous sites. On the other hand domestic chickens, which we all take for granted today, were only introduced to Britain during the late Iron Age/early Roman period, and rabbits were not introduced until the at least the 11th century AD.
The sieving of soil samples from features such as ditches and pits found on archaeological sites helps us to recover bones from small mammals such as rodents, and from small birds. Most of these would have been living wild, in and around past human settlements. They can help us to form a picture of the local environment. Black rats are commonly associated with urban settlements, whereas hares thrive in open grasslands and field systems. The bones of birds and fish that were eaten help to build our picture of past diet and resource exploitation; fish are also a very good indicator of trading links, as marine fish, oysters and mussels are often found on inland sites and must have been brought from the coast.
Animals also seem to have had an important ritual significance for people in the past. Some may have been considered sacred, and some may have been associated with particular forms of religious rites, or social customs. Animals were sacrificed in religious ceremonies, and ritual or customary feasts may have involved the consumption of particular kinds of meat, sometimes in large quantities. We still have conventions about food and festivals today, with our traditional Christmas or Thanksgiving turkey and Easter lamb. Quite often we find that complete animals have been buried in key places around a site, such as in the ditches of round houses during the Iron Age, in isolated pits, or with the burial of a human being. Possible ritual deposits of this type are often identified because the complete skeleton has survived with all the bones in their natural position (‘articulated’). This implies that the animal had been buried whole and had not been cut up into meat joints for human consumption (see figure 5 below).
Figure 5: A Neolithic/Bronze Age cattle burial found in a shallow pit from the site at Yarnton Floodplain. There were no other associated objects with the burial (click on the image to view in more detail).