The so-called "relics of Joan of Arc," overseen by the Archbishop of Tours in Chinon, France, do not contain the charred remains of the Catholic saint.
Rather, the artifacts consist of a mummified cat leg bone and human rib, both dating to the 6th-3rd century B.C., according to a new study.
The "relics," which have fooled onlookers for decades, did resemble burnt bones, in keeping with historical accounts of the death of Joan of Arc (ca. 1412-1431), who was convicted of heresy and executed by burning.
Medical examiners, pathologists, geneticists, biochemists, a radiologist, zoologist and archaeologist all participated in the extensive study, which was accepted for publication in the journal Forensic Science International.
The bottle containing the bones first surfaced at a pharmacy in 1867. Its label read: "Remains found under the pyre of Joan of Arc, maiden of Orleans."
Different techniques, including DNA analysis, several forms of microscopy, chemical analysis and carbon dating, were used to examine the bottle's contents.
A few years ago, Philippe Charlier, a forensic scientist at Raymond Poincare Hospital in Garches, France, and his team first determined that the bottle contained an approximately 4-inch-long human rib covered with a black coating. It also housed part of a cat femur covered with the same coating, three fragments of "charcoal" and "a brownish textile scrap" about the same length as the rib.
Charlier said some historians then speculated that a cat, perhaps symbolizing the devil, was thrown onto Joan of Arc's funeral pyre.
Carbon dating, however, found that the objects predate the French heroine's lifetime by many centuries.
The "textile scrap" is likely a mummy wrapping, since "the chemical composition of the coatings was comparable with that of embalming products, such as those used by the old Egyptians," the researchers concluded.
The dark coating contained a mix of bitumen, wood resins, gypsum and other chemicals. Pine pollen was also identified, probably from pine resin, commonly used during Egyptian embalming.
The researchers believe the remains were first stored as "mummia," which were parts of Egyptian mummies used in medieval pharmaceuticals. Medieval medicine, for example, may call for a compress made of a mummy bit and the juice of an herb (Bursa pastoris) to stop nosebleeds.
"The question remains of why there was an interest in manufacturing a historical forgery during the 19th century, especially one concerning Joan of Arc," the researchers wrote, wondering if the forgery surfaced for political reasons in order to tap into her legacy.
"Or is it only an act of hoax," the researchers asked, "a joke of a medical student who would have been taken much too seriously?"
Archaeologist Anastasia Tsaliki of the University of Durham called it a "fascinating project," demonstrating how "palaeopathology" can be used to inform history.
The objects are now at Chinon's Museum of Art and History, located in central France.