Image: Evolutionary tree by Charles Darwin

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

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