It might be the very first evolutionary ‘Tree of Life’ ever made, with the branches representing the divergence of species. It’s a concept that we’re all very familiar with now, but in Darwin’s time this was a completely new idea.

Darwin wrote everything he thought of down in a few notebooks, titled simply “A”, “B”, “C”…, "Books to be read”, or sometimes had nothing at all on the cover. He took them with him on his voyage on the Beagle to the Galapagos islands, where he wrote them full of theories about biology and geology - for example, he came up with the idea that atoll islands are formed by coral reefs (which ended up being true!). His “B”, “C”, and “D” booklets were all titled “Transmutation” which he would later rename to be “evolution”. The drawing above is from notebook “B”, and shows a genealogy. At the bottom (at the “1”) it has the first ancestor, and after that various species branch off. Wherever a branch ends with a perpendicular line that particular species has gone extinct, and those that don’t have the line are still living today. In booklet “D” you can find Darwin’s theory of evolution in a draft form which Darwin had thought of at the time.

The notebooks have always been housed in Cambridge, Darwin’s university. But at the end of November 2020 it turned out that booklets “B” and “C” were not there any more! They have last been seen in 2000, after which the curators thought the little box they were in had just been misplaced. Twenty years later that doesn’t seem so plausible any more, and the curators now think they have been stolen. So, if you come across a few small notebooks with a badly drawn Christmas tree, please contact Cambridge University!