Darwin continued to research and extensively revise his theory while focusing on his main work of publishing the <answer>scientific results of the Beagle voyage</answer>. He tentatively wrote of his ideas to Lyell in January 1842; then in June he roughed out a 35-page "Pencil Sketch" of his theory. Darwin began correspondence about his theorising with the botanist Joseph Dalton Hooker in January 1844, and by July had rounded out his "sketch" into a 230-page "Essay", to be expanded with his research results and published if he died prematurely.
What information was Darwin's essay based on?
scientific results of the Beagle voyage