After an extensive search of the library at Cambridge University in the UK, curators have come to the conclusion that Charles Darwin's famous notebooks, where he fleshed out his ideas about an evolutionary tree following his world trip on the HMS Beagle, have been stolen rather than merely lost.

The books, known as the Transmutation Notebooks, contain Darwin's first musings on how species might "transmute" into a later species from their ancestral form. They also include his famous "Tree of Life" sketch.

First listed as missing in 2001, the University now accepts they have been taken, and on November 24 launched a public appeal for help in locating them, on the anniversary of the publication of Darwin's seminal work On the Origin of Species, on November 24, 1859. 

Usually stored in the Special Collections strong room where the rarest books are kept under a close eye, they were removed to be photographed in 2000. A year later the library was doing a routine check when they noticed the notebooks were missing, as well as the small box they were placed in. The library is pretty labyrinthian, and staff initially assumed that they were simply lost in the storerooms, in a sea of around 10 million books, manuscripts, and maps. According to the University, the library contains more than 210 kilometers (130 miles) of shelving.

Searches have been launched over the years, but following the latest thorough exploration of the Darwin Archive and the storage facility, theft is now suspected, the police have been informed, and the notebooks have been added to Interpol's database of stolen artworks, Psyche.

The library is appealing for any information that may help with the return of the books.

As for how the theft happened, they're not quite sure, though security has tightened since they were reported missing.

“Security policy was different 20 years ago," Dr Jessica Gardner, University Librarian and Director of Library Services said in a statement. "Today any such significant missing object would be reported as a potential theft immediately and a widespread search begun. We keep all our precious collections under the tightest security, in dedicated, climate-controlled strong rooms."

The University and Cambridge Police hope the appeal will help jog someone's memory and lead to information that may result in the books' return. "Due to the time since their disappearance, information from the public will be very important to this investigation," Detective Sergeant Sharon Burrell said.

Anyone with information can contact ManuscriptAppeal@lib.cam.ac.uk and remain anonymous if they wish.

2020 has been a surprisingly good year for the return of stolen objects. In January, Alan Turing's degree and OBE medal were returned 36 years after they were stolen by a fan in England. In April, an ancient relic from the City of David was returned for fear of retribution from a coronavirus-related apocalypse, and in October artifacts stolen from Pompeii were sent to Italy in the mail from Canada to break a 15-year-long "curse". Here's hoping the thief of Darwin's notebooks feels that after a good 19-year run, it's time to return them home.