2 valuable Charles Darwin notebooks not seen for 20 years probably stolen, experts fear

An example of an identical box and notebook is seen from the library's Darwin Archive. (Provided Photo/Cambridge University Library via CNN)

(CNN) — Two notebooks that once belonged to Charles Darwin, believed to be worth millions of pounds, have “likely been stolen” after being missing for two decades, Cambridge University Library said Tuesday.

The notebooks — one of which contains Darwin’s 1837 “Tree of Life” sketch — had been removed from the university’s special collections strong rooms, where rare and valuable items are kept, to be photographed in September 2000, the library said in a statement.

The items were logged as photographed in November of the same year, but a routine check in January 2001 found that the small box containing the books had not been returned to its correct place.

Darwin sketched his ideas around an evolutionary tree in the summer of 1837 after returning from his round-the-world trip aboard HMS Beagle — decades before he published more developed ideas around the tree of life in “On the Origin of Species.”

For years, librarians at the university had assumed the books, known as the “Transmutation Notebooks,” were simply lost in the vast library, which is home to more than 210 kilometers (about 130 miles) of shelving and some 10 million books, maps, and manuscripts.

After an “exhaustive” search for the items, which, according to the university, are likely worth “millions of pounds,” the books are considered missing and likely to have been stolen.

“I am heartbroken that the location of these Darwin notebooks, including Darwin’s iconic ‘Tree of Life’ drawing, is currently unknown, but we’re determined to do everything possible to discover what happened and will leave no stone unturned during this process,” Jessica Gardner, university librarian and director of library services since 2017, said in a statement.

“We would be hugely grateful to hear from any staff, past or present, members of the book trade, researchers, or the public at large, with information that might assist in the recovery of the notebooks. Someone, somewhere, may have knowledge or insight that can help us return these notebooks to their proper place at the heart of the UK’s cultural and scientific heritage,” she added.

The missing items have been reported to Cambridgeshire police, and have been recorded on the national Art Loss Register for missing artifacts, as well as Interpol’s Psyche database for stolen artworks.

The missing notebooks had previously been digitized and are available on the Cambridge Digital Library. The university plans to continue its search for the documents, and a complete search of the building, home to one of the world’s most significant collections of Darwin’s works, is expected to take five years.