It seemed like the perfect forensic tale. Earlier this year, a geneticist concluded that the remains of a blood-soaked cloth stored for centuries in an 18th century gourd likely belonged to the severed head of the last French king, Louis XVI—a conclusion supported by the fact that the DNA matched that taken from a mummified head belonging to his direct ancestor, King Henry IV. So confident were some people about the findings that a company now offers a blood test for anyone who wants to see if they, too, are descendants of this royal family.But new research released today calls into question the identities of both the blood and the head, arguing that the DNA in those samples does not match the DNA in living relatives of these kings. The data “make a strong case,” against the previous work, says Cristian Capelli, a geneticist at the University of Oxford in the United Kingdom who was not involved with the work.According to legend, when King Louis XVI was beheaded in 1793 during the French Revolution, a witness soaked up his blood with a handkerchief and stored it in a decorated gourd. A few years ago, the family that owned the gourd asked geneticist Carles Lalueza-Fox of the Institute of Evolutionary Biology in Barcelona, Spain, to look at the DNA from the remains of the cloth. At the time, all he could say was that the DNA came from a blue-eyed European male because he didn’t have any DNA from any of the king’s relatives. 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Henry IV was a direct ancestor of Louis XVI, so a match would provide further evidence that the blood belonged to the French king. Lalueza-Fox was able to isolate a small amount of Y chromosome from the inner part of the head, which is transmitted from male to male each generation. Enough of it matched the blood’s Y chromosome for him to conclude that the blood and head came from individuals who were related to each other.French historian Philippe Delorme wasn’t convinced. There was so little Y chromosome from the head that the matchup could have been by chance. He teamed up with geneticist Jean-Jacques Cassiman from the Catholic University of Leuven in Belgium and identified three living descendants of the French kings, members of the House of Bourbon, to find out what the Y chromosome of that lineage should look like. They analyzed the Y chromosomes of these male relatives, and came up with a “Bourbon” Y chromosome profile. That profile did not match that obtained from the blood and head, Cassiman, Delorme, and their colleagues report today in the European Journal of Human Genetics.Who is right depends in part on what the Bourbon family tree really looks like—and that is also under dispute. Cassiman and Delorme argue that the three relatives they analyzed come from different branches of the tree, so the matching parts of their Y chromosome indicate true Bourbon inheritance. But Lalueza-Fox and his French historian collaborator Philippe Charlier think that the living relatives all trace back to Philippe I, who was homosexual and thus perhaps unlikely to have actually fathered the next generation. “It seems likely that what we have here is just a case of false paternity within a royal family,” says Lalueza-Fox, who sticks by his original work. “Moreover, we should be cautious with the genealogies claimed by people. These are often less accurate than we may think.”Both sides think the best way to get to the bottom of this forensic tale would be to study the DNA of more living relatives. But neither has the funds to do so. So for now, the new work “leaves still open the hunt for true remains of these historical figures,” Capelli says.