DNA Finally Reveals How Famous Medici Princes Died

A long-circulating Medici murder rumor just hit a scientific wall. New DNA analysis of the remains of two 16th-century brothers from the powerful Florentine dynasty shows they died of malaria, not arsenic poisoning, researchers report in the journal iScience. An international team tested bone samples from Cardinal Giovanni de Medici, who died at 19 in 1562 around the same time as his mother and younger brother, and Grand Duke Francesco de Medici, who died at 46 in 1587 alongside his wife, per Live Science. They found genetic traces of Plasmodium falciparum—the deadliest malaria parasite—in both men, matching contemporary accounts that described a recurring "tertian" fever.

Francesco's bones also carried Plasmodium malariae, indicating a double infection that may have contributed to his and his wife's rapid decline. The findings undercut suspicions that a rival brother, Cardinal Ferdinando de Medici, engineered their deaths and fit with the family's habit of retreating to mosquito-ridden Tuscan estates where malaria lingered into the 20th century, per Yale News. The study also aids efforts to track the spread of malaria during the Renaissance. Giovanni's infection came from a previously unknown strain of P. falciparum with two novel mutations, offering new clues to how the disease evolved in Europe and how the pathogen adapts over time. Further genetic work may clarify how these ancient strains relate to each other.