For most modern people, the story of Marie Antoinette ends with her death. For some, though, it didn't end until 1998, when one of the most credible pretenders to the throne of France was, posthumously, discredited. See how genetics solved a 200-year-old mystery.
Marie Antoinette's story has become a sort of legend. Whether it's imagined as the martyrdom of a powerless pawn or the comeuppance of a callous plutocrat, it has both the perfect stage and the perfect timeline. In the narrative, the curtain closes with the fall of the guillotine. Real life wasn't as precise; both Louis XVI and Marie Antoinette were widely seen as martyrs by their contemporaries, but more significantly, they were seen as royals. That meant that whoever inherited the throne could get both their tragic glamour and, eventually, the wealth of the restored crown.
The couple had two living children at the time of their deaths, Marie Therese and Louis Charles. The law forbid a woman from ever inheriting the throne of France, and so all the hopes of the royalists fell on Louis Charles. The hopes were dashed when Louis Charles died at the age of 10, only two years after his parents' deaths and while still in the custody of the radical republicans of France.
Rumors swirled about his fate. Most believed that his jailers had killed him (historians generally think it was tuberculosis), but more intriguing gossip hinted that he'd escaped. Long after the Terror was over, a number of different Louis Charleses popped up around Europe. One new worlder even claimed the throne, saying he had been taken in by "tribes in America." The most credible candidate was a German clock-maker named Karl Wilhelm Naundorff. Naundorff, despite speaking limited French, convinced much of the old French court, and gained a spectacular coup when he won the recognition of Louis Charles' nanny. "Louis XVII" is even written on his gravestone, albeit under his instructions.
Although Naundorff's claims were never accepted officially, there was no way to absolutely disprove his story until genetic testing came into the picture. Marie Therese, the only child of Louis XVI and Marie Antoinette to survive the Terror, never had children, and so there were no direct descendants from whom to get samples. There are genetic benefits, though, to being part of a big family. Marie Antoinette was the daughter of the Austrian empress Maria Theresa, who had sixteen children. Many of them married royals and had children of their own. There are surviving descendants from the maternal line. And not all genetic material has to come from living people. Marie Antoinette herself had a habit of exchanging locks of hair with her family. Because she became so famous at the time of her death, hair samples from both Marie Antoinette and two of her sisters survive.
Samples of bone marrow were taken from the grave of Naundorff — don't pretend to be royalty if you don't want your body exhumed — and scientists did a mitochondrial DNA analysis. The mitochondria is the cell's energy converter; without it, there would be no point in consuming glucose, because it would never been turned into something that the cell can use. We picture all human DNA being packed into the cell's nucleus, but mitochondria, out floating in cytoplasm, have their own set of genes dubbed mitochondrial DNA, or mtDNA. Although both sperm and egg have mitochondria, and mitochondrial DNA, the mtDNA in sperm simply disintegrates upon fertilization of the ovum. The ovum's mtDNA is replicated, and stays with a person for life. Mitochondrial DNA is then passed down through the female line. Although a boy will have his mother's DNA, he will not pass it on.
The mitochondrial DNA in the hair samples from Marie Antoinette and her sisters all matched. Close relatives — those of the same generation — will match very closely. As time passes, mutations emerge in the mtDNA. It takes a little more research to see if differences in DNA are due to time or to lack of a blood relationship. Naundorff's DNA had two nucleotide differences from the hair samples. He had four nucleotide differences from the surviving relatives. He, most likely, was not in any way related to the executed queen.
What about the other Louis Charles candidates? They were excluded by a more grisly test. Reportedly, a royalist had come into the possession of the heart of Louis Charles. He smuggled it away. This is not as horrific as it sounds — the internal organs, including the heart, were often removed from the corpses of French royalty and preserved in ceremonial urns. Monks or court officials would kneel by these urns and venerate them. The plan might have been to do such a thing for the young boy, who, in the eyes of the royalists, had become king after his father hand been executed. The heart survived, mummified, to this day, and after the claim of Naundorff was disproved, the heart was tested at two different laboratories. The mitochondrial DNA matched the mtDNA in the hair samples exactly. Sadly, the young boy did die in prison in 1795, and the Louis Charles pretenders were just pretenders. After 200 years, there is no more speculation.