Whose severed head was on display in the ancient Egypt exhibit? That was the question facing curators at the Museum of Fine Arts in Boston, Massachusetts, back in 2009.

A 4,000-year-old mummy’s head had been found in 1915 in a looted tomb in the Egyptian necropolis of Deir el-Bersha, about 140 miles south of Cairo. The tomb was the final resting place for a governor named Djehutynakht (juh-HOO-tuh-knocked) and his wife, who lived around 2000 b.c. But experts weren’t sure whether it was his head or that of his spouse.

To learn the mummy’s identity, scientists removed one of its teeth and tried to test its DNA, something that had never been done on a mummy. But the attempts were never successful. Finally, in 2016 the Federal Bureau of Investigation (F.B.I.) offered to help. A team of forensic scientists trained to extract DNA from extremely old bodies drilled into the tooth to make a powder. The scientists were able to obtain DNA and soon had their verdict: The head belonged to the governor himself.

Not only did unraveling the mystery help identify the mummy, but the method could help in future investigations. Says Pontus Skoglund, a geneticist at The Francis Crick Institute in London: “It’s one of the holy grails of ancient DNA to collect good data from Egyptian mummies.”