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126 The Tree of Life Charles Darwin’s first known sketch of an evolutionary tree, circa 1837, from his early notebooks for The Origin of Species. I think Case must be that one generation then should be as many living as now. To do this & to have many species in same genus (as is) requires extinction. Thus between A & B immense gap of relation. C & B the finest gradation , B & D rather greater distinction. Thus genera would be formed. —bearing relation. ...

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