Image: Evolutionary tree by Charles Darwin
Charles Darwin's sketch from 1837, his first diagram of an evolutionary tree from his ‘First Notebook on Transmutation of Species’ (1837) - on view at the Museum of Natural History Manhattan, NYC.
Interpretation of handwriting: "I think case must be that one generation should have as many living as now. To do this and to have as many species in same genus (as is) requires extinction . Thus between A + B the immense gap of relation. C + B the finest gradation. B+D rather greater distinction. Thus genera would be formed. Bearing relation" (next page begins) "to ancient types with several extinct forms".
- Charles Darwin
- © Public Domain