Irish Teeth Reveal the Chemical Signature of the Great Famine


The Custom House Famine Memorial in Dublin. Image credit: William Murphy via Flickr // CC BY-SA 2.0

The Great Famine in Ireland, one of the worst starvations in human history, lasted from 1845 to 1852. Sometimes called the “Irish Potato Famine” due to a disease that ravaged the crop that many Irish diets were based on, this period saw the population of Ireland decrease by about one-quarter. Around 1 million people died from starvation and other diseases, while another million or so left Ireland for new lives elsewhere in Europe and the U.S. While historically, the famine is well known, research into its physical effects is a comparatively new topic in archaeology.

A novel study by Julia Beaumont of the University of Bradford and Janet Montgomery of Durham University, published recently in PLOS One, tackles the question of how to identify famine and other chronic stress from specific skeletons. They focus their analysis on human remains from the Kilkenny Union Workhouse in southeast Ireland, just one of the many workhouses that sprang up after 1838, when a law was passed to help “remedy” poverty by institutionalizing the poor and making them work long hours. Individuals and entire families would enter the workhouse, which was segregated by age and sex, overcrowded, and full of sick people.

At least 970 people were buried in mass graves at Kilkenny, in unconsecrated ground. The researchers focused on the teeth of 20 of them, representing a cross-section of age and sex. Six had died before age 9.

The failure of the potato crop shortly after the emergence of Irish workhouses meant reduced food for the poor and, as a consequence, a significant amount of sickness and death among this vulnerable population. Although the government was slow to respond to the food crisis, eventually it began to import corn from America to feed the poor. And this introduction of corn is particularly helpful archaeologically, because corn's chemical composition is very different from that of potatoes and Old World grains. Archaeologists who analyze human bones and teeth can see the dramatic differences in corn-based and wheat-based diets by measuring the ratio of the two carbon isotopes in the skeleton.

The first important finding from Beaumont and Montgomery’s study is that, for many of the 20 people they analyzed, they could see the carbon isotopes rising after the start of the Great Famine. By micro-sampling the dentine portion of teeth at various stages of formation, they show an increase in corn consumption through time that correlates well with historical information about diet.

But their second finding is even more intriguing: Even as carbon isotopes increased, the nitrogen isotopes decreased. Archaeologists use nitrogen isotopes to understand the amount of protein in a diet. If you are a carnivore and eat food high on the food chain, you have a higher nitrogen isotope signature than if you are a vegetarian. The drop in nitrogen isotopes the researchers found in the teeth that occurred after the introduction of corn does not track with historical records; there is no known change in the protein that the poor were eating at this time.

Beaumont and Montgomery argue that the change in isotopes reflects a cycle of starvation. The high nitrogen values prior to the introduction of corn don't suggest these people had a lot of meat protein to eat. Instead, these isotopes most likely indicate that their bodies, starving, were in a sense eating themselves, by recycling their own protein and fat. When the Kilkenny workers started eating corn, their nitrogen values dropped as their bodies were able to use corn for survival.

The researchers say the “famine pattern” in this historic Irish population is therefore one of average carbon values paired with high nitrogen values, followed by higher carbon and lower nitrogen values when corn is introduced to stave off starvation.

Beaumont and Montgomery see this pattern in the teeth of children who died in the workhouse during the famine, but also in the teeth of some of the adults. Since teeth form during childhood, this finding suggests that the adults suffered from—and overcame—one or more periods of chronic stress prior to the Great Famine. These stresses might have been caused by famine, but prolonged disease can leave similar isotopic traces, so they can't say for sure the adults experienced multiple periods of starvation.

This research comes at a time when micro-sampling of teeth is becoming a popular technique in archaeology. A recent study by researchers at McMaster University, for example, micro-sampled tooth dentine to look at cases of rickets, a deficiency of vitamin D.

Beaumont has plans to expand this research and to correlate this new methodology with other techniques useful for finding evidence of famine. “I have some teeth from other populations with nutritional deficiencies which I am micro-sampling to try to achieve a resolution that matches the physical signs, such as enamel hypoplasias," Beaumont tells mental_floss. (An enamel hypoplasia is a defect in tooth enamel.) "I want to work with others in the field to investigate the histology.”

Studies into ancient diets are not just useful for archaeologists; sadly, starvation and famine are not things of the past. Their findings can also be used by forensic anthropologists investigating recent deaths, especially, as the researchers write, “of populations and individuals for whom nutritional stress may have contributed to their death.” This work may prove critically important in the future for solving forensic cases of fatally malnourished children.

As for the skeletal remains of the 20 people studied—they were all re-interred at the Famine Memorial Garden in Kilkenny.