Researchers at Yale University say they have used ancient DNA analysis to resolve a centuries-old mystery surrounding the death of Grand Duke Francesco I de' Medici, ruler of Renaissance Tuscany, debunking long-standing rumours that he was poisoned. The findings, published in the journal iScience, matter because they overturn a theory that has persisted since the 16th century about one of Italy's most powerful and famous ruling families.

Francesco I de' Medici died suddenly in 1587, with his wife, Bianca Cappello, dying just a day later after both fell ill with intermittent fevers. Their near-simultaneous deaths, which followed a stay at a mosquito-infested villa, fuelled centuries of speculation that the couple had been murdered by poisoning, but the new genetic evidence points instead to a natural cause.