Genetic tests on rib bones from Francesco I and Giovanni de’ Medici found Plasmodium falciparum in both men, with Francesco also carrying P. malariae, pointing to malaria rather than murder.
The iScience study directly challenges the long-running claim that Francesco was poisoned in 1587 by his brother Ferdinando, who inherited the Tuscan throne after Francesco and his wife died a day apart.
Researchers said the DNA evidence matches historical reports of intermittent fevers and Francesco’s final illness after a hunting trip in marshy Tuscan areas where mosquito-borne disease was common.
Giovanni’s sample also contained a previously uncharacterized P. falciparum strain with 2 unique mutations, giving scientists new evidence on how the malaria parasite evolved in Europe.
The findings reinforce earlier work on other Medici deaths and show how ancient DNA can resolve disputed historical deaths while tracing the history of deadly pathogens.