Nearly 6,000 years ago, a young woman in what is now Denmark chewed and spit out a piece of gum. She couldn’t have imagined that millennia later, scientists would use it to discover clues about her life—including where she came from, what she looked like, and even what she ate.

Researchers found the preserved gum at an archaeological site dating from the Stone Age—a prehistoric period when humans used stone tools. The gum was made from birch tree bark, heated until it became black and sticky. Ancient people used the substance, called pitch, as glue. The woman had been chewing the pitch to soften it before using it to stick stone blades onto wooden handles.

As the woman chewed the gum, she left behind some of her DNA—the molecule that carries hereditary information. Much of the DNA was damaged because it was so old, says Hannes Schroeder. He’s a molecular anthropologist who studies ancient human DNA at the University of Copenhagen in Denmark. But enough DNA remained to get a surprisingly full picture of the woman’s life.

Based on her genes, or units of DNA responsible for a person’s traits, she most likely had blue eyes and dark skin and hair, says Schroeder. These were typical characteristics of people living in the region at the time, he adds. Also stuck in the gum was duck and hazelnut DNA. “That material likely came from something the woman had recently eaten,” says Schroeder.