In 1587, Grand Duke Francesco I de' Medici and his wife, Bianca Cappello, died just one day apart after suffering high fevers. The physicians who treated them concluded that malaria was the cause.

Many people didn't believe them.

Francesco's ambitious brother, Ferdinando, inherited the throne almost immediately, fueling rumors that the couple had been poisoned with arsenic. Over the centuries, that theory became one of the Renaissance's most enduring mysteries, appearing in books, documentaries, and historical accounts. Some modern researchers even claimed to find evidence of arsenic in Francesco's remains.

More than 400 years later, scientists returned to the case with a tool the Renaissance physicians never had: ancient DNA.

The new study found DNA from Plasmodium falciparum, the deadliest malaria parasite, along with evidence of a second malaria infection. The findings strongly support what the Medici physicians concluded in 1587: Francesco most likely died of malaria, not murder.

Sometimes modern science overturns history. Sometimes it confirms that people living centuries ago understood more than we give them credit for.