Two notebooks used to illustrate Charles Darwin's theory of evolution are missing and believed to have been stolen some 20 years ago. Cambridge University Library made the announcement Tuesday, saying an "extensive search" had failed to locate the leather notebooks Darwin wrote shortly after his return from the Galapagos Islands in 1837, which are together worth millions of dollars, per the Telegraph. They were last seen in November 2000, when they were taken from a special manuscripts storeroom to be photographed, reports the BBC. Records show they were taken to a temporary building on the grounds of the university library during extensive construction work following "an internal request." Two months later, in January 2001, the small blue box that contained the notebooks was found to be missing from its proper place during a routine check.
"My predecessors genuinely believed that ... [the notebooks] had been mis-shelved or misfiled," Jessica Gardner, who's served as university librarian since 2017, tells the Guardian, which reports the library contains more than 130 miles of shelving. "Reluctantly I have decided that was not the right conclusion," she adds, per the Telegraph. Thorough searches, including one in the Darwin archive earlier this year, have failed to locate the notebooks—which include Darwin's famous "Tree of Life" sketch, introducing the notion of the evolutionary tree—and the assumption is that they were stolen. Interpol has been notified while the library appeals for information from the public. Tips can be sent to firstname.lastname@example.org. Though the notebooks have been digitized, Gardner says heartbroken officials "will leave no stone unturned." (Read more Charles Darwin stories.)