A centuries-old mystery surrounding the Medici brothers may finally be solved after researchers found genetic evidence that both were infected with the malaria parasite Plasmodium falciparum. The findings challenge long-standing speculation that political intrigue or poisoning caused their deaths.
Instead, the study suggests malaria may have played a key role in one of the Renaissance’s most debated family tragedies.
The study, led by Alexander Ochoa and published in iScience, analyzed skeletal remains belonging to Grand Duke Francesco I de’ Medici and his younger brother, Cardinal Giovanni de’ Medici. Researchers recovered ancient DNA from malaria parasites preserved in their bones for more than 400 years. They also identified a previously unknown strain of P. falciparum, offering new insight into the history of malaria in Renaissance Italy.
A family tragedy that fueled centuries of speculation
The Medici family was one of the most powerful ruling dynasties of the Renaissance. Yet the deaths of Francesco and Giovanni have remained the subject of debate for generations.
Historical records show that Giovanni became seriously ill in 1562 after traveling through the marshes of Tuscany, where malaria was widespread. His mother, Eleonora of Toledo, and his brother Garzia also developed severe fevers during the same journey. All three died within about four weeks.
Francesco died 25 years later after visiting a Medici villa surrounded by rice fields, an area known at the time for unhealthy conditions and malaria. His wife, Bianca Cappello, died the following day after suffering similar symptoms.
Because the couple died so close together, rumors spread that Francesco had been poisoned with arsenic by his brother Ferdinando during a power struggle. Those claims have remained part of Renaissance history for centuries.
Ancient DNA reveals evidence of malaria
To investigate the long-standing mystery, researchers extracted DNA from rib bones belonging to both brothers. They then used targeted genetic techniques to search for DNA from several malaria-causing parasites.
The analysis detected parasite DNA in both men. The strongest evidence came from Giovanni, whose remains contained enough genetic material to clearly identify Plasmodium falciparum, the species responsible for the deadliest form of malaria.
A centuries-old mystery surrounding the Medici brothers may finally have an answer. Ancient DNA recovered from their remains revealed evidence of Plasmodium falciparum, suggesting malaria may have played a key role in their deaths. pic.twitter.com/yze4Mm4P1E
— Tom Marvolo Riddle (@tom_riddle2025) July 1, 2026
Francesco’s remains contained much smaller amounts of parasite DNA, making the results less certain but still consistent with malaria infection.
The recovered DNA fragments were very short and showed the chemical changes expected in ancient genetic material. Those patterns support the conclusion that the DNA is authentic rather than the result of modern contamination.
Researchers identify a previously unknown strain
By comparing the ancient DNA with malaria genomes from Europe and other parts of the world, researchers found that Giovanni carried a previously uncharacterized strain of P. falciparum. The strain appears to be closely related to ancient malaria parasites that circulated in Europe, including strains previously identified from Austria, southern Italy and France.
The genetic analysis suggests the parasite was likely part of a population that had already spread across Europe centuries before the Renaissance. However, researchers caution that the limited number of ancient malaria genomes available today makes it impossible to determine the strain’s exact origin with confidence.
The findings do not end the debate completely
The researchers emphasize that finding malaria DNA does not prove the disease was the direct cause of death. Instead, the evidence confirms that Giovanni was infected with P. falciparum and that Francesco also carried malaria parasite DNA.
Combined with historical reports describing repeated high fevers before their deaths, the findings strengthen the case that malaria contributed to the brothers’ final illness.
Researchers also note that Francesco’s sample contained only a small amount of parasite DNA. They cannot rule out the possibility that he carried more than one malaria species because mixed infections were not uncommon in Europe during that period. Additional testing of the remains could provide clearer answers.
New clues to the history of malaria
Beyond the Medici family, the study offers a rare glimpse into the evolution of one of humanity’s deadliest diseases.
Malaria shaped life in many parts of Italy for centuries, especially in marshy regions where mosquitoes thrived. Although the disease was eventually eliminated from Europe during the 20th century, P. falciparum continues to cause hundreds of millions of infections worldwide each year.
The newly identified Renaissance strain expands the known genetic diversity of ancient malaria and fills an important gap in the historical record. It also demonstrates how advances in ancient DNA research can help answer historical questions that written records alone have left unresolved.
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