Photograph of sheep bones in a laboratory
Labelling a sheep skeleton. Initiated in the 1990s, the ‘Medieval Wool’ or ‘Sheep’ project, is leading to an improved understanding of how sheep were bred and managed in the past. © Historic England
Labelling a sheep skeleton. Initiated in the 1990s, the ‘Medieval Wool’ or ‘Sheep’ project, is leading to an improved understanding of how sheep were bred and managed in the past. © Historic England

The Sheep Project: Helping Us Understand Wool Production in the Past

Research by Historic England Zooarchaeologists is investigating how we can detect evidence for wool production from archaeological sheep bones and teeth. The wool industry was a key driver of the medieval and post-medieval economies in England. Various farming methods have been used to improve the quantity and quality of wool, including sheep breeds, part of the fleece used, and feeding regimes. Traditionally, sheep were often castrated to enhance the quality of wool.

Zooarchaeological evidence for wool production

In assemblages of archaeological animal bones we see evidence for intensification of wool production from the medieval and early post-medieval periods, through increasing use of adult sheep and high proportions of males. However the identification of castrated animals (called wethers) is problematic.

Developing a research collection

In order to improve methods for identifying wethers in archaeological assemblages and to investigate other aspects of sheep management in the past, we are studying a large collection of sheep (Ovis aries) skeletons with known life history. The sheep are of the unimproved Shetland breed, chosen because it is one of the smallest British breeds of sheep and is thought to closely resemble prehistoric and early historic animals. The exact age (in days), sex (female, male or wether), and quality of nutrition were recorded in detail, allowing us to explore the effects of each factor  on the size, shape, and growth of bones and teeth.

Identifying sheep management

In line with previous studies we have shown that the size and shape of bones can vary between sexes. For example, some bones of wethers are longer and more slender than those of rams. Our research has shown that the shape of part of the pelvis (hip) joint allows complete separation between rams and ewes, while wether pelves are intermediate – the potential blurring of shape distributions may therefore indicate the presence of wethers.

Bone growth is also affected by castration, particularly in the process of epiphyseal fusion, the joining of bone ends or articulations with the central shaft of limb bones. Our study shows that fusion is severely delayed in wethers, compared to ewes and rams. In contrast, teeth show a different growth pattern, erupting at about the same time in all three, but generally wearing down faster in rams and wethers as they get older.

Comparing bone fusion and tooth data is a possible tool for studying the composition of archaeological sheep flocks, with high proportions of unfused bones (from seemingly young animals) along with heavily worn teeth (of older animals) indicating the presence of wethers.

We are currently studying these patterns in archived data and collections to see if the pattern is similar in other breeds and regions, and might therefore be applicable to a wide variety of archaeological assemblages.

Related research

In addition to the research by HE specialists, many external researchers use our sheep collection. Isotope analysis, analysis of biochemical signatures in animal tissues relating to environment, diet and geographical origin, has been applied to wool and bone samples helping us to understand how and why these signatures vary between and within flocks. This will assist us in studying husbandry and movement of sheep populations as well as production and trade in artefacts of bone, horn and wool.

Polydora Baker

Senior Zooarchaeologist

Polydora Baker is Senior Zooarchaeologist at Historic England. She is a co-founder of the Professional Zooarchaeology Group (PZG) and has recently published Animal Bones and Archaeology: Guidelines for Best Practice, with co-author Fay Worley and many external colleagues. She is continuing research into sheep husbandry based on modern and archaeological skeletal collections.

Contact Polydora Baker

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