Osteological analysis for the Round Mounds project of the Isle of Man (Part One)

Author: Michelle

Rachel was kind enough to ask me to write this week’s blog post about the human osteology component of the Round Mounds project. This will be a two-part post as in the first instance I would like to talk a little bit more generally about what I do as an osteologist or bioarchaeologist and what kind of things can we learn from human skeletal remains. In the second post, I will take you through some of the material that I have examined at the Manx National Museum and talk a little bit about what questions we have answered and more even more exciting, what questions we have raised.

So to begin, what is an osteologist? ‘Osteo’ is derived from the Greek word for bone, so at its most basic – an osteologist is someone who studies bones. This can apply to any skeletal material, human or animal, so I would classify myself at a human osteologist, meaning I only look at human bones. The term bioarchaeologist is a slightly contentious one, as it can be used to describe anyone studying biological material from an archaeological context, such as seeds, animal bones or plant material. However, in the past few decades, those who study human remains (i.e. bones, mummies, hair, nails, etc… in this case, only bones are present) have come to appropriate the term and use what is called the bioarchaeological framework – which just means we use human remains to answer problem-oriented archaeological questions rather than just compiling biological data. A bioarchaeologist, or biological anthropologist uses human remains to study a variety of areas in the past such as who the people were, where they came from, what kind of illnesses they had, what they did and how they lived. In order to do this, some basic fundamental data needs to be collected regarding all the human remains present in a collection.

What is the process of the osteological analysis?

The first step to any analysis of human remains is to determine what is present and how it relates to the excavation contexts. This is particularly true when dealing with material from excavations from a long time ago. It is important to know where the bones you are looking at have come from not only the site, but also the location within the site. Good excavation methodology can provide a lot of information regarding burial practice – this information will be lost if the bones are not recorded properly in the field. As well, appropriate packaging and labelling of the bones in the field will allow the post-excavation analysis to provide even more information about the burial practices present and the person being buried. In the 19th century and through to the early 20th century the information which could be derived from human skeletal material was considered limited and therefore, skeletal material was often either not kept or not kept in the best of conditions. All of these aspects of excavation and post-excavation curation and practices will have an effect on the information which can be derived from the skeletal material.

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Excavation of the Bishopscourt Cist Burial on the Isle of Man

 

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Site plan of West Kimmeragh noting the location of a cremation pit alongside the container from the field which contained the bones. Recording the location the bones come from is very important.

Now that we know what where the human remains have come from, we can make some observations about their appearance. Is it only bone and teeth or are there other tissues present? Assuming that we most often are dealing with bones, we then need to determine their preservation status. Are they burned? Are they clean? Do we need to sieve to separate them from the soil or stones which were excavated with them? What colour are they? What is the general state of their surface preservation and how stable are they?

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Cleaning and sorting the bones for preliminary analysis. Note the fine 1mm sieve on the right.

 

 

The majority of the skeletal material from the Neolithic and Bronze Age burials on the Isle of Man is burned or cremated. The term cremated means to use fire to reduce the human remains to bone and dust and involves burning of a body or part of a body. Quite often in the past, this would have taken place on a pyre. Bone that has been heated looks very different from bone which has not been. There are changes in colour, fracturing and breaking of the bone and the changes in the cell structure of the bone due to heat application results in the bones feeling different from unburned bone. Both cremated (on left side) and unburned bone (right side) separated for recording. From Cronk y Vowlan, Kimmeragh, Bride.

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Both cremated (left) and uncremated bone (right) separated for recording from Cronk Y Vowlan

 

Bone preservation on the Isle of Man is quite poor. The acidity of the quite peaty soil causes the unburned bones to break down quickly, disintegrating to leave nothing but organic stains or if they survive to become quite breakable with a highly eroded exterior surface. This must of course lead us to the question of whether there is a predominance of cremation burials in the prehistoric periods on Mann, or is it simply that cremated burials survive to a greater extent than the un-burned bones. This kind of question will be difficult to answer, but by combining the excavation records with the osteological analyses, we will be able to put together a clearer picture of the nature and practice of mortuary behaviours in the Neolithic and Bronze Age.

 

Cremated bones are quite often gathered up and put into some kind of receptacle – such as a bag or a pot, or directly into a pit or grave in the ground. The bones are mixed together and often are mixed with left over fragments from the burning process. Once in the laboratory, we need to separate the bones from the soil and pyre debris. To do this, I sieve the bones and pick them out from the small stones and other objects. Sometimes they require a bit of brushing to remove any remaining soil adhered to them. Once they are clean, I can then separate them into different types of bones – cranium (head) and teeth, long bones (from the arms and legs), irregular shaped bones (from the shoulder or hips) and small bones of the hands and feet (such as the wrist bones or fingers). The high level of fragmentation and the shrinkage and warping which is associated with burning bones makes it difficult to identify all the fragments of bone. In some cases it is only possible to say that something is a long bone fragment, in other cases, depending on the fragment that is present, I can identify which specific bone it is and which side of the body it comes from.

So what am I looking for and what can I learn from cremated bone?

When I am sorting the bones and identifying them, I am looking to see if I can find any multiples of a particular part of a bone. This will help to tell us how many people are included within a particular burial context. For example, there is a dense bone within your skull that forms a part of your ear, called the petrous (pyramid or portion); this bone survives cremation well, is relatively easy to identify and can be sided easily. Therefore, if you have two left petrous’ you can be certain that you have at least two individuals present within the sample you’re looking at. Portions of bone like the petrous are considered diagnostic, and can be used to determine the minimum number of individuals present. Other aspects which must be considered when trying to determine the minimum number of individuals are age and sex.

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Right (on the right side) and left (on the left side) petrous bones indicating there are a minimum of three individuals in this deposit.

 

The age-at-death of an individual is assessed using either bone and tooth development or bone and tooth degeneration. Scales of assessment have been created to place developing or degenerating bones and teeth into likely age ranges. There are a number of different factors which can effect the growth and/or degeneration of an individual (i.e. lifestyle, activity, health, nutrition), so these ranges must be applied cautiously. Another complicating factor in using dentition, is that the hard enamel shell of teeth usually explodes during cremation leaving only the root, which means that unless the tooth is still forming, it cannot be used for age assessment. The sex of an adult individual (there is no way to visually determine the sex of a child), is determined from various features of the skull and pelvis. Unfortunately, the cremation process usually destroys the bones of the pelvis and we are left with small fragments of cranial features which can be used, but again must be used cautiously, to provide a sex identification for the individual.

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Fragment of a lower jaw (or mandible). Large fragment like this can hep with age and sex assessments.

 

Once I have an idea of the minimum number of individuals present and the age and sex of those individuals, I will try and look for any abnormalities in the bones which may be able to tell me something about the health of the person or if they have any genetic traits which could be interesting across a population. Bones and teeth will change in response to some chronic illnesses or things which occur during the course of life, like injury or nutritional deficiencies. Cremated bone unfortunately provides a more limited amount of information regarding health and disease as there is usually bone missing and that which is there, is highly fragmented. There are several inherited discreet traits which can be observed on skeletal material which can provide some insight into genetic links amongst a population. Overall, looking at one individual is interesting to understand that person’s experiences, but it is when a larger population sample is examined that we can begin to discuss patterns and aspects of beliefs and life ways within communities.

Human remains from archaeological sites provide the most tangible link to the people of the past. The osteological analyses of the bone from the Neolithic and Bronze Age burials on the Isle of Man will be able to contribute a greater understanding about the prehistoric Manx people in several areas: burial practices and belief systems; health and disease; population demographics; life ways and activities; population mobility; and diet and nutrition. The next osteology blog post will explore a bit more about where the bones have come from that I looked at, what I was able to find out about individuals at several sites, and further information what the bones of the Manx prehistoric peoples can tell us about the past.

For more information on cremation: Ubelaker, D. (2009). The forensic evaluation of burned skeletal remains: A synthesis Forensic Science International, 183 (1-3), 1-5 DOI: 10.1016/j.forsciint.2008.09.019. Or there is a nice blog post to synthesize cremation here: https://bonesdontlie.wordpress.com/2011/11/01/experiments-for-understanding-cremated-remains/

Cheers, Michelle

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