Ancient DNA Overturns a 400-Year-Old Medici Poisoning Theory

07.15.2026 // 1 MIN READ // Dead Curious

Key points

Yale researchers extracted ancient DNA from the skeletal remains of Grand Duke Francesco I de' Medici, who died suddenly in 1587 amid rumors he'd been poisoned with arsenic.
The genetic analysis found two species of Plasmodium parasites -- the cause of malaria -- rather than any evidence of arsenic poisoning.
It's the first time ancient DNA has been used to conclusively confirm a Medici family member's cause of death, according to the study published in iScience in 2026.

For more than four centuries, the sudden 1587 death of Tuscany's Grand Duke Francesco I de' Medici fueled rumors that he and his wife had been poisoned. New ancient-DNA testing from Yale University now points to a far less dramatic killer: malaria.

Why it matters

It's a rare case where modern genetics can definitively settle a centuries-old rumor of murder among European royalty, replacing speculation with a verifiable cause of death.

What to watch

The Yale team says the same ancient-DNA approach could be applied to other unsolved royal and noble deaths where poisoning was long suspected but never proven.

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Sources

CNN Yale News