Teeth reveal clues about people’s diet during the Irish Famine

An example of Killkenny dentitions (Queen’s University Belfast/PA)

Belfast Telegraph.com.uk

The mid-19th century famine wiped out around a million people after the potato crop failed in successive years.

Teeth analysed from the 1840s have shed new light on what people ate before and during the Irish Famine.

Scientific analysis of dental calculus – plaque build-up – of the Famine’s victims found evidence of corn, oats, potato, wheat and milk foodstuffs.

Researchers also discovered egg protein in the calculus of three people, which they said is more associated with diets of non-labouring or better off social classes at the time.

The mid-19th century famine wiped out around a million people after the potato crop failed in successive years.

It shows how the notoriously monotonous potato diet of the poor was opportunistically supplemented by other foodstuffs, such as eggs and wheat, when made available to them Dr Jonny Geber

Researchers analysed teeth from the human remains of 42 people, aged around 13 years and older, who died in the Kilkenny Union Workhouse and were buried in mass burial pits on its grounds.

The workhouse pits were discovered in 2005 and were found to contain the remains of nearly 1,000 people.

Potato and milk was virtually the only source of food for a vast proportion of the population in Ireland.

Many people were forced to seek refuge in the workhouses during the Famine, where they received meagre rations of food and shelter in return for work.

Researchers examined samples of calculus for microparticles and protein content linked to foodstuffs.

The microparticles showed a dominance of corn, as well as evidence of oats, potato and wheat.

The corn came from so-called Indian meal, which was imported in vast amounts to Ireland from the United States as relief food for the starving populace.

Analysis of the protein content identified milk, as well as the occasional presence of egg.

One of the lead researchers, Dr Jonny Geber of the University of Edinburgh’s School of History, Classics and Archaeology, said: “The results of this study is consistent with the historical accounts of the Irish labourer’s diet before and during the Famine.

“It also shows how the notoriously monotonous potato diet of the poor was opportunistically supplemented by other foodstuffs, such as eggs and wheat, when made available to them.

“The Great Irish Famine was one of the worst subsistence crises in history but it was foremost a social disaster induced by the lack of access to food and not the lack of food availability.”

The study is published in the Proceedings of the National Academy of Sciences of the United States of America.

The study is a collaboration between researchers from the Universities of Edinburgh, Harvard, Otago in New Zealand, York, Zurich, and the Max Planck Institute for the Science of Human History in Germany.

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“WHODUNNIT” OF IRISH POTATO FAMINE SOLVED

Topic: The potato

It is the first time scientists have decoded the genome of a plant pathogen and its plant host from dried herbarium samples. This opens up a new area of research to understand how pathogens evolve and how human activity impacts the spread of plant disease.

Phytophthora infestans changed the course of history. Even today, the Irish population has still not recovered to pre-famine levels. “We have finally discovered the identity of the exact strain that caused all this havoc”, says Hernán Burbano from the Max Planck Institute for Developmental Biology.

Many intact pieces of DNA

For research to be published in eLife, a team of molecular biologists from Europe and the US reconstructed the spread of the potato blight pathogen from dried plants. Although these were 170 to 120 years old, they were found to have many intact pieces of DNA.

“Herbaria represent a rich and untapped source from which we can learn a tremendous amount about the historical distribution of plants and their pests – and also about the history of the people who grew these plants,” according to Kentaro Yoshida from The Sainsbury Laboratory in Norwich.

Irish potato famine pathogen

The researchers examined the historical spread of the fungus-like oomycete Phytophthora infestans, known as the Irish potato famine pathogen. A strain called US-1 was long thought to have been the cause of the fatal outbreak. The current study concludes that a strain new to science was responsible. While more closely related to the US-1 strain than to other modern strains, it is unique. “Both strains seem to have separated from each other only years before the first major outbreak in Europe,” says Burbano.

The researchers compared the historic samples with modern strains from Europe, Africa and the Americas as well as two closely related Phytophthora species. The scientists were able to estimate with confidence when the various Phytophthora strains diverged from each other during evolutionary time. The HERB-1 strain of Phytophthora infestans likely emerged in the early 1800s and continued its global conquest throughout the 19th century. Only in the twentieth century, after new potato varieties were introduced, was HERB-1 replaced by another Phytophthora infestans strain, US-1.

Several connections with historic events

The scientists found several connections with historic events. The first contact between Europeans and Americans in Mexico in the sixteenth century coincides with a remarkable increase in the genetic diversity of Phytophthora. The social upheaval during that time may have led to a spread of the pathogen from its centre of origin in Toluca Valley, Mexico. This in turn would have accelerated its evolution.

The international team came to these conclusions after deciphering the entire genomes of 11 historical samples of Phytophthora infestans from potato leaves collected over more than 50 years. These came from Ireland, the UK, Europe and North America and had been preserved in the herbaria of the Botanical State Collection Munich and the Kew Gardens in London.

“Both herbaria placed a great deal of confidence in our abilities and were very generous in providing the dried plants,” said Marco Thines from the Senckenberg Museum and Goethe University in Frankfurt, one of the co-authors of this study. “The degree of DNA preservation in the herbarium samples really surprised us,” adds Johannes Krause from the University of Tübingen, another co-author. Because of the remarkable DNA quality and quantity in the herbarium samples, the research team could evaluate the entire genome of Phytophthora infestans and its host, the potato, within just a few weeks.

Crop breeding methods may impact on the evolution of pathogens. This study directly documents the effect of plant breeding on the genetic makeup of a pathogen. “Perhaps this strain became extinct when the first resistant potato varieties were bred at the beginning of the twentieth century,” speculates Yoshida. “What is for certain is that these findings will greatly help us to understand the dynamics of emerging pathogens. This type of work paves the way for the discovery of many more treasures of knowledge hidden in herbaria.”

Original article:
past horizons
May 22, 2013

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