What we eat and the way we live can leave traces on our bodies even long after we're gone, discovers Darina Daly.
Among the latest crop of reality TV shows is an offering from Channel 4 called You Are What You Eat, in which nutritionist Dr Gillian McKeith browbeats nutritionally challenged participants into changing their ways.
By examining their diet, taking blood samples and having a peculiar fixation on "pooh", McKeith is able to see exactly what a person is doing to their bodies by the food they eat.
The rationale behind McKeith's methods is not new. Most of us, bombarded with information on food and diets, are aware that the way we live and the food we eat will leave a visible trace on our bodies.
What we might not realise is that how we live remains evident long after we've gone. "Virtually everything that you do in your life will leave a trace on your body," says Laureen Buckley, an osteo-archaeologist who has examined human remains from archaeological sites across Ireland.
Human teeth, for example, tend to survive well given good conditions. Buckley points out that if a person had a lot of infections or nutritional deficiencies as a young child, when the teeth are forming, this would show up as lines on the teeth. In terms of diet, it has been proven that people in prehistory had a lot of wear on their teeth from the grit found in roughly ground flour.
She can also distinguish pre-Medieval from post-Medieval remains due to the "phenomenal rise in the amount of caries" (tooth decay) after the introduction of refined sugar in the Medieval diet.
By contrast, modern teeth show virtually no wear because we eat soft, processed foods, although, according to Margot Brennan of the Irish Nutrition & Dietetic Institute, modern teeth are more prone to erosion from consuming too much citric acid found in soft drinks and even carbonated water.
Osteo-archaeologists are specialists in human remains and carry out examinations in order to provide information on sex, age, height, build, health and possibly occupation. Their work is an important component of archaeology which attempts to reconstruct past human lifeways by studying the physical or material remains of past human groups.
Buckley has worked on human remains, either whole skeletons or more fragmentary finds, from all periods. For Buckley, the key is trying to reconstruct the life of the individual being examined.
"One of the first questions people ask is how did they die, but you can very rarely tell the cause of death of a skeleton unless it's been beheaded or there's an arrowhead still in it - even then you can't say which wound killed a person, just that these wounds happened around the time of death."
A good example would be a collection of skulls found in a ditch near Dunamaise castle in Co Laois. She could tell that the victims had been beheaded and their teeth indicated a very poor diet. "You can imagine that these were poor peasants caught up some sort of rebellion," she says.
As an independent specialist, she is called to a variety of sites if there is a possibility that bones have been discovered. "The first thing I do is establish how old the bones are and make sure they're ancient before we proceed."
Radiocarbon dating is carried out in Belfast or Groningen in the Netherlands, to firmly establish the age of the remains. However, in many instances, there are enough clues to establish on site that the remains are not modern.
In a recent case, a farmer in Liscooley, near Castlefinn, Co Donegal contacted Buckley because he thought he had discovered a cist, or a stone-lined grave, on his land. A small early Bronze Age cemetery was examined and among the finds was the crouched burial of a 12-year-old child beside a decorated pot.
Establishing the age of a skeleton is not as easy as determining its sex, which is seen through the shape of the pelvis and skull. By judging the development of bone and teeth, a person can be aged accurately up to 25, after that it is more imprecise.
"For archaeological purposes, we put them into a broad band of young adult, adult and older adult," she says.
In determining age and sex, a broad population picture can be built up, and, although this depends on the population in question - for instance, a monastery site will have predominately male burials - it is possible to see patterns in terms of health, diet and life expectancy.
Buckley worked on the Medieval cemetery of the abbey of St Thomas the Martyr in Dublin, excavated by Claire Walsh of Archaeological Projects Ltd. Most of the burials dated from the late 13th to early 14th century and she found little evidence of nutritional deficiencies indicating it was a well-off population, a fact backed up by historical evidence.
Another indicator that these people enjoyed a rich and plentiful diet was evidence of diseases associated with obesity. One particular disease - diffuse idiopathic skeletal hyperostosis (DISH) - has been found both in Ireland and England, mainly on friary or monastery sites, and there is thought to be a link with mature onset diabetes which is linked to obesity.
Such diseases are visible on these sites because the monks were well fed, says Buckley. "It can also indicate different status amongst a population from perhaps a poorer site."
A number of bone conditions give direct and indirect evidence of nutritional deficiencies including tibial periostitis and enamel hypoplasia. They can reveal whether a person was deficient in vital nutrients like vitamin C or vitamin D which can cause rickets. Anaemia or iron deficiency can also be detected.
Brennan says vitamin D is found in oily fish and through exposure to sunlight and is necessary for calcium absorption. "Foods like red meat, chicken, offal and egg yolk all provide Haem iron and are well absorbed into the body, whereas the other type of iron, which comes from nuts, leafy vegetables, peas and beans, needs to be eaten with foods rich in vitamin C like oranges so they can be absorbed by the body."
Bones can also be examined for infectious diseases, some of which will turn up as a particular pattern on the bones, for example, Tuberculosis can leave traces such as collapsed vertebrae or periostitis on the ribs.
Buckley recently completed an examination of bones held in the National Museum of Ireland. Project director Mary Cahill asked her to re-examine a collection of Bronze Age burials, among them a female skeleton.
CT scanning of the bones at the Beacon Clinic in Sandyford revealed that the woman had primary bone cancer. "There were some obvious lesions on her skull and long bones, and she would have suffered terribly."
Skeletal remains can also indicate a person's lifestyle, for instance, if they were involved in heavy labour or other physical activity on a regular basis. Four Viking burials discovered in South Great George's Street in Dublin were examined by Buckley during an excavation carried out by Linzi Simpson of Margaret McGowen and Co Ltd last year.
"They were all males, mostly young, muscular and tough. I could tell this by the muscular insertions on their shoulders and arms," she says. A shield found with one of the burials indicated that the deceased had been a Viking warrior.
More detailed examination, such as isotopic analysis, can determine the kind of diet a person enjoyed, for example, a mainly marine or terrestrial one. Strontium analysis is used to indicate where people may have lived or moved from during their lives. However, this kind of analysis has only being taken up recently in Ireland, says Buckley.
One thing that Buckley is adamant about is the dangers of inferring too much information when examining skeletal remains.
"There is a record of a person's life in the bones. You can look for joint disease, arthritis, degenerative diseases. Even if people had worked when they were young, it shows up in the bones."
But beyond the scientific analysis, she is wary of interpretation: "Say I've got two burials [an adult and child\] in a double grave, and people say this must be a mother/daughter or father/son, but all I can say is that they died at the same time and were buried together. We can't assume because we bury families in the same plot nowadays that's what they did in the past."
As more discoveries are made due to an increase in archaeological investigations in recent years, more information is being gathered about how our ancestors lived. For Buckley, that is the essence of her work. "I love writing the reports because I love putting it all together, seeing what I can figure out about the lives of people."