On 11th January 1844, Charles Darwin, in rather long-winded fashion, came clean to his friend Joseph Dalton Hooker:
Besides a general interest about the Southern lands, I have been now ever since my return [from the Beagle voyage] engaged in a very presumptuous work & which I know no one individual who wd not say a very foolish one.— I was so struck with distribution of Galapagos organisms &c &c & with the character of the American fossil mammifers, &c &c that I determined to collect blindly every sort of fact, which cd bear any way on what are species.— I have read heaps of agricultural & horticultural books, & have never ceased collecting facts— At last gleams of light have come, & I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable.
Joseph Dalton Hooker was one of the first people Darwin confided in regarding his heretical evolutionary views. He chose his friends well. They had only been corresponding with each other for two months, but Hooker was to remain one of Darwin’s most staunch allies for the rest of Darwin’s life.