Centuries of speculation surrounding the death of Grand Duke Francesco I de' Medici have been addressed by new DNA analysis, which suggests malaria, not poison, was the cause of his demise in 1587. Researchers at Yale University examined ancient DNA from the Grand Duke's skeletal remains, alongside those of his brother, Giovanni de' Medici, who died 25 years earlier. The findings, published in the journal iScience, indicate the presence of malaria parasites in Francesco I de' Medici's bones.
Francesco I de' Medici and his wife, Bianca Cappello, both fell ill with intermittent fevers after staying at a villa known to be mosquito-infested. Their rapid deaths fueled persistent rumors that they had been poisoned, with suspicion often falling on Francesco's brother and rival, Cardinal Ferdinando de' Medici. However, the study identified genetic traces of Plasmodium falciparum, the parasite responsible for the deadliest form of malaria, in the Grand Duke's remains. Additionally, molecular traces of P. falciparum and P. malariae were found.
The research team, led by Yale anthropologist Serena Tucci, also discovered a novel strain of P. falciparum in the remains of Giovanni de' Medici. While malaria was common in Renaissance central Italy and contemporary physicians' reports described symptoms consistent with the disease, the absence of definitive scientific evidence allowed poisoning theories to flourish.
"The results are scientific proof to dispel persistent speculation that Francesco de Medici was poisoned to death," Yale officials stated. Archival sources from court physicians described symptoms consistent with malaria, then referred to as "febbre terzana," and noted treatments such as bloodletting, which could have been detrimental.
While the researchers cannot entirely exclude the possibility of poisoning, Tucci emphasized that malaria remains the most plausible explanation. "We can only say that we found the pathogen that causes malaria in this specimen, confirming that he had malaria," she said. The study marks the first time the brothers' skeletal remains have been genetically analyzed, offering scientific confirmation of earlier historical evidence of malaria.
The same genetic approach used in this study could potentially help solve other historical mysteries, according to co-author Gisella Caccone, a senior research scientist at Yale. She noted that such methods can be applied when there is a clear hypothesis to investigate and the necessary genomic tools are available. Furthermore, the identification of the new malaria strain could aid researchers in understanding the parasite's evolution over time, potentially contributing to improved control methods.