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Jawing About French King Louis IX’s Jawbone

A scientific investigation of King Louis’ jawbone is interesting, as is an investigation of the skeletons in his closet.

Pathologists study the causes and effects of disease mostly through laboratory examination of samples taken from body tissues. But what does a paleopathologist do? Given that “paleo” comes from Greek for “ancient,” it makes sense that a paleopathologist studies ancient diseases by examining mummified tissue and skeletal remains. For example, the jawbone of Louis IX, King of France from 1226-1270. Although the history of this relic has been supposedly well documented, researchers led by paleopathologist Philippe Charlier were allowed to use modern techniques to investigate the jawbone’s authenticity. Dr. Charlier had achieved previous fame by confirming that teeth fragments stored in the Russian state archives were indeed those of Adolf Hitler. The Fuhrer, contrary to tabloid headlines, had not escaped to Argentina.

Now back to Louis IX. The king was a devout Catholic bent on driving Muslims out of the Holy Land. In 1270, he led the 8th Crusade with a plan to capture Tunis from where he would march on to Jerusalem. The assault fizzled as Louis’ army was ravaged by disease, debated by historians as being either the plague or dysentery. What is known for certain is that the king was not spared and met his end laid out on a bed of ashes in the form of a cross as a final penance. The custom at the time for revered rulers was to segment the body so that parts could be interred in several places allowing for widespread worship of the remains. Louis’ body was eviscerated and the skeletal remains dispersed. The jawbone finally ended up in the Cathedral of Notre Dame and the intestines, after being boiled in wine and spices for preservation, were laid to rest at the Cathedral of Versailles.

In 2016, Dr. Charlier’s group received permission to examine a sample of the preserved intestines by scanning electron microscopy. They found remnants of Schistosoma, a parasitic worm, suggesting that Louis suffered from Schistosomiasis, characterized by abdominal pain, diarrhea and bloody stools. This water-borne disease is also called “snail fever” since the parasites are released into water by freshwater snails. Charlier does not think that the king died from the disease since it takes seven weeks for symptoms to occur after contact with the parasite and Louis landed in Africa only four weeks before his death. He likely contracted and survived the disease on a previous Crusade.

The jawbone, which Charlier had a chance to investigate in 2020, suggested another affliction. Lesions in the bone were found to be consistent with scurvy! This seems to be backed up by contemporary accounts that describe the king losing teeth and spitting out bits of gum. Scurvy is marked by a deficiency in vitamin C which Louis may well have suffered from due to his piety and poor diet. Penance was an integral part of the king’s life; he wore “hair shirts” for discomfort, flagellated himself, and often fasted. When he wasn’t fasting, he subsisted mostly on fish as documented by the king’s chronicler, Jean de Joinville, who also described how soldiers “howled like women in labour” when dead tissue had to be cut from their gums so that they could chew their meat. Had they been chewing on fruits and vegetables the problem would not have occurred, but these were not part of the Crusaders fare. The claim isn’t that Louis died of scurvy, just that the ailment weakened him and made his less resistant to the dysentery that probably killed him.

Of course, the speculation about Louis’ health is only relevant if the jawbone is really that of the king. The Charlier group tackled this problem by resorting to radiocarbon dating, a technique for which University of California chemist Willard Libby received the 1960 Nobel Prize in Chemistry. Radiocarbon dating is based on the fact that the carbon atoms in our body come from the plants that we eat either directly, or via animals that have eaten plants. Plants in turn get their carbon from carbon dioxide in the air. A tiny, tiny percent of the carbon atoms in that carbon dioxide have eight neutrons in their nucleus instead of six. These C-14 atoms are radioactive, meaning that they slowly emit an electron and convert into nitrogen which is stable and not radioactive. It takes 5700 years for half the C-14 atoms in a sample to be converted to non-radioactive nitrogen. As long as a plant or animal is alive, the C-14 content gets constantly replenished from the carbon dioxide in the air, but after death, there is no more such replenishment. By comparing the radioactivity of a substance that once was part of a living species, such as bone, to that found in currently living plants, it is possible to calculate the age of the bone.

In the case of Louis IX, radiocarbon dating indicated that the jawbone was about fifty years too old to belong to the king. But Charlier rationalized this discrepancy by noting that that the results were likely skewed by Louis’ fish diet. Fish spend their lives in water from which they absorb bicarbonate ions that in turn come from deposits of calcium carbonate such as coral. Such deposits were formed millennia ago, meaning that they have virtually lost all their C-14 content. On a diet of fish, some of this ancient carbon gets absorbed into the system which means that when it comes to radiocarbon dating, the bones of a fish eater will appear to be older than they really are.

As may be expected, the investigation of King Louis’ innards and jawbone garnered much media attention but also received some criticism from other paleopathologists who raised questions about the methodologies used and “definitive” conclusions arrived at. That controversy notwithstanding, the extensive media coverage did introduce the public to the fascinating field of paleopathology. But it is not only the king’s jawbone that is involved in a controversy. So is his bronze statue, first displayed in St. Louis in 1906, the city that was named by French fur traders after the king who was canonized as “Saint-Louis” by Pope Boniface VIII in 1297.

Why did a French king receive such an honour? Because Louis was a fervent advocate of Christianity with a history of charitable acts towards the poor and waging battles with Islam on behalf of the faith. He built the magnificent Saint Chapelle in Paris to house what he be believed to be a piece of the original Cross and the Crown of Thorns worn by Jesus. But Louis’ history also has a messy side. Under his rule blasphemy was punished by mutilation of the tongue and lips. As a protector of the “true faith,” he persecuted Jews because they had denied the deity of Christ. In 1240, under and edict from the king, the “Disputation of Paris” put the Talmud, the major source of Jewish commentaries on the Bible and religious law, on trial. The Talmud was declared to be anti-Christian and resulted in Louis ordering that all copies of the Talmud in Paris be collected and burned. Twenty-four cartloads of the books, all handwritten since this was long before Guttenberg’s invention of the printing press, were gathered and burned. Later, in 1269, he ordered Jews to listen to missionary sermons and wear a distinctive badge, predating Nazi orders by eight hundred years. He also planned the eventual expulsion of Jews but dysentery caught up with him before the plan could be put into practice.

It is Louis’ zealotry on behalf of his faith that has embroiled his statue in controversy. Some demonstrators have urged that it should be removed because of his racism, others maintain that the statue should stay put because it enshrines the battle for the one true faith. That is one argument that will not be settled by paleopathologists.


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