Safe in a museum vault in Mexico City sits a mysterious book that’s been the source of controversy for decades. Known as the Grolier Codex, the book was discovered by looters in a Mexican cave in 1965. They claimed it dated back hundreds of years, but experts dismissed it as a fake. Now, after half a century, researchers have determined that the text is not only real, it’s also the oldest book ever found in the Americas. To figure out the truth, a team from Yale University in Connecticut and Brown University in Rhode Island analyzed the book’s pages and found that both the paper and ink were types used by the Mayan people, who lived centuries ago in what is now Mexico and Central America.* The year the book was found provided another clue: In 1965, scholars didn’t yet know about some of the ancient gods depicted in the text, meaning the book couldn’t have been forged. And carbon dating verified that the text is about 800 years old. Researcher Stephen Houston says the document could provide new insights into Mayan culture: “It gives us a glimpse into life during a time we don’t fully understand.”