London — Two of's notebooks containing his pioneering ideas on evolution and his famous "Tree of Life" sketch are missing, believed stolen, the Cambridge University Library said on Tuesday. The British scientist filled the leather notebooks in 1837 after returning from his voyage on the HMS Beagle. The library said they were worth millions of pounds.
In one book, under the simple heading, "I think," he drew a diagram showing several possibilities for the evolution of a species and later published a more developed illustration in his 1859 book "On the Origin of Species.
The University of Cambridge's vast library first listed the notebooks as missing in 2001 after they were moved out of the Special Collections Strong Rooms to be photographed in a separate, temporary building amid construction work.
They were long believed to have been incorrectly filed within the building following that excursion. Cambridge's library contains around 10 million books, maps and manuscripts and has one of the world's most significant Darwin archives.
However a major search this year — the largest in the library's history — failed to turn up the notebooks.
"Curators have concluded the notebooks... have likely been stolen," the library said in a statement.
It said it had informed local police and the books had been listed on Interpol's database of stolen artworks, called Psyche.
The University Librarian, Jessica Gardner, released a video statement appealing to the public to help.
"It is deeply regretful to me that these notebooks remain missing despite numerous wide-scale searches over the last 20 years," she said, adding that the library has since massively improved its security systems with both technology and tighter protocols for staff.
The statement released by Cambridge noted that the search for the books would continue inside its cavernous library because, while they suspect theft, they cannot yet rule out misplacement.
Cambridge said its Special Collections Strong Rooms alone were home to some 28 miles of shelving. It would take the school at least another five years to finish scouring that space for any sign of the missing books.
The librarian suggested that former or current library staff, those working in the book trade or researchers could have information.
"I would ask anyone who thinks they know of the notebooks' whereabouts to get in touch. Please help," she said.
The appeal was launched on November 24, known as Evolution Day as it marks the date of the publication of "On the Origin of Species."