Genetics Rewrites Renaissance Mystery: Francisco de' Medici Likely Died of Malaria, Not Poison

Centuries of Renaissance mystery surrounding the deaths of Grand Duke Francesco I de' Medici and his wife Bianca Cappello may finally be solved, with new genetic analysis pointing to a fulminant form of malaria as the cause, rather than the long-suspected poisoning by his brother.

Researchers from the Universities of Pisa and Turin, in collaboration with Yale University, successfully sequenced the genetic profile of a microorganism found in the Grand Duke's ribs, whose remains are interred in the Medici Chapels in Florence. The results, according to Valentina Giuffra, a paleopathology expert at the University of Pisa, provide "definitive proof" supporting the diagnoses made by the court physicians in 1587. Historical chronicles from that era accurately described intermittent fevers and high temperatures, which the physicians treated with bloodletting.

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For us, it was a very high certainty because historical sources already described fevers treated with bloodletting that accelerated the death, but now the DNA evidence gives us absolute confirmation.

"For us, it was a very high certainty because historical sources already described fevers treated with bloodletting that accelerated the death, but now the DNA evidence gives us absolute confirmation," Giuffra stated. The study, published in the scientific journal iScience, directly refutes a 2006 investigation by the University of Florence. That earlier research claimed arsenic poisoning based on an analysis of alleged visceral remains and beard hair.

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Even if they found arsenic, it is not certain that it belonged to Francesco I; there were only bones in the tomb.

Giuffra criticized the 2006 work for lacking methodological rigor, noting that no facial hair was ever found in the ducal tomb and that it was biologically impossible to attribute the viscera found in urns to the Grand Duke. "Even if they found arsenic, it is not certain that it belonged to Francesco I; there were only bones in the tomb," she asserted.

Suspicion of murder arose in 16th-century Florence due to the close proximity of the couple's deaths, just one day apart, and the known discord between Francesco and his younger brother, Cardinal Fernando, who immediately assumed power. However, clinical records from the time indicate both had contracted the infection after visiting marshy areas, and the medical treatment applied proved counterproductive. "A patient already weakened by malaria who undergoes frequent bloodletting becomes even weaker, which accelerated his death," explained the University of Pisa expert.

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A patient already weakened by malaria who undergoes frequent bloodletting becomes even weaker, which accelerated his death.