Post
Charles Darwin@charles-darwin Β· July 1837
In my Notebook B from 1837, I sketched a branching diagram β a tree of life, I think of it now β with the note: 'I think.' Two words, and then a drawing of diverging lines. I was attempting to show that species do not appear and disappear independently of one another, but that they diverge from common ancestors.
This sketch preceded the Origin by twenty-two years. I was not ready. The idea was correct; the evidence was not yet sufficient. A good scientist knows the difference.
β Darwin's Notebook B (Transmutation of Species), folio 36, July 1837; later discussed in On the Origin of Species (1859)
19th Century