For three strange weeks 200 years ago this past summer, France’s countryside was gripped by an inexplicable terror.

Rumors swept through towns and villages that bandits were about to seize the year’s grain harvest. Peasants, weeping and shouting, took to the woods with pitchforks and muskets. Others crisscrossed the countryside in a blind panic, looting and burning chateaux and so terrifying the French aristocracy that they took steps to abolish what was left of the ancien regime, France’s pre-revolution social order.

La Grande Peur of 1789 is considered a pivotal event in the history of the French Revolution.

But, like so many of the outbreaks of panic and bizarre behavior of medieval and early modern Europe, how and why it happened remain a puzzle to historians.


Why, for example, did it occur in some parts of France but not in others? Why did the hysteria appear to affect entire communities simultaneously instead of spreading from house to house and town to town as panic ordinarily would? And what possible explanation, psychological or otherwise, could there be for spontaneous mass psychosis?

According to a study by Mary Kilbourne Matossian, a University of Maryland historian, the mystery of La Grande Peur can be explained by the rye bread that was the bulk of the diet of French peasants of the period.

Drawing on historical records, Matossian argues that the French countryside was in the grip of a massive outbreak of food poisoning brought on by a fungus that grows on rye grain and that produces a natural form of the hallucinogen LSD.

Matossian’s arguments appear in her recently published book, “Poisons of the Past: Molds, Epidemics, and History,” a sweeping reinterpretation of European and American history in light of what people ate.


In everything from the Black Plague of the 14th Century, to the witch trials of Salem, Mass., the religious revivals of the 18th Century and the population explosion of the early industrial revolution, Matossian maintains that serious outbreaks of microbiological contamination of the food supply played a large role in shaping social behavior and population patterns.

“Some of her conclusions may be exaggerated,” said William McNeill, a University of Chicago history professor. “It is almost always the case that when you find something new and write about it, the result is a rather lopsided picture. But she is on to a very significant point. This is something historians simply haven’t thought of.”

Matossian’s focus is on a fungus known as ergot, a highly toxic mold that under certain climatic conditions--cold winters and wet, warm summers, in particular--can grow and infect rye.

Ergot is the fungus from which LSD was originally extracted.


When consumed, even in minute quantities in flour made from infected rye, ergot can cause an astonishing range of symptoms--including gangrene, fertility suppression, loss of motor control and severe hallucinations, delusions and even death.

Ergot poisoning was a risk in pre-modern Europe, because, until the potato became the dietary staple of the lower classes in the late 18th and early 19th centuries, peasants north of the Alps and Pyrenees and those in Russia were heavily dependent on rye, a hardy crop that can grow in extreme climates and poor soils.

By some estimates, peasants in the region ate as much as two to three pounds of rye bread a day, making them particularly susceptible to ergot poisoning when conditions favored its development.

Matossian’s approach is to try to account for outbreaks of bizarre behavior in a given area by looking at local food consumption patterns and climatic conditions over the previous growing season.


In 1789, for example, the year of La Grand Peur, “France had not seen weather conditions so favorable to the growth of ergot on rye . . . since 1697, when reasonably complete records were first kept,” she writes.

First, an unusually cold winter weakened the rye, which is planted in the fall for harvest the following spring. A cold and humid spring then allowed the fungus to grow on the plants; a warm dry May promoted the spread of fungal spores; the warm, wet summer that followed was ideal for the formation of toxic alkaloids.

Matossian uses the same analysis to explain the peculiar phenomenon of witch trials, which periodically gripped different parts of Europe in the Middle Ages.

The symptoms normally associated with bewitchment, she says, are strikingly similar to the central nervous system disorders caused by ergotism: tremors, parasthesias (sensations of pricking, biting ants crawling on the skin), spasms, seizures, contractions of the face and eyes, hallucinations and panic attacks.


The parts of Europe where witch trials were most common were cold and wet areas where rye was the staple. By contrast, in Ireland--where the peasant diet consisted mainly of dairy products and oats--witch trials were rare.

Matossian is not the first to link witch persecution with food poisoning. At least one other researcher has suggested that ergotism played a role in the Salem witch trials of Colonial Massachusetts, a conclusion Matossian supports with evidence of an unusual amount of rye eating in Salem at the time of the outbreak and ideal climatic conditions in the previous year for ergot growth.

Matossian’s most original work concerns the historical debate about the causes of the European population explosion of the mid-18th Century.

Some historians have proposed “the potato theory” of population growth, arguing that the introduction of the potato into the diet of northwestern Europe in the early 1800s so improved agricultural production that it was possible to sustain a larger population.


To the potato theory, which has been attacked as an insufficient explanation for the dramatic population gains between 1750 and 1850, which in England and Wales averaged some 300%, Matossian adds a critical addendum: Perhaps, she says, the switch from cereals to potatoes helped population growth by eliminating a source of ergot toxins, which suppressed fertility and increased mortality.

In Russia, where dietary changes happened much later than in Western Europe, Matossian cites statistics that show that as the consumption of rye dropped from 40.8% of total starches to 20.6% between 1885 and 1926--and potatoes grew from 17.5% to 37.4% in the same period--infant mortality dropped from 274 per thousand births to 172 and the death rate dropped from 34 per thousand to 19 per thousand.

Matossian’s evidence, throughout her book, is not proof. It is based on correlations, which are notorious for their potential to mislead.

“I have written this book with a keen sense of limitation,” she said.


“There is a great deal of this kind of (correlative) hypothesis behind some of her assertions, and in that sense she is on treacherous ground,” McNeill said.