Notebook 'B', as he labelled it, is now often – not quite accurately – cited as the place where Darwin first hit upon his theory of evolution by natural selection. It owes this fame to his 'tree of life' diagram, which shows multiple species diverging from a common ancestor, some falling extinct as others survive.
The laconic opening – 'I think' – describes process, rather than conclusion, and this diagram didn't represent the end point of his quest, but a staging post.
"The Notebook: A History of Thinking on Paper" - Roland Allen














