When Joseph Dalton Hooker published his third and final essay on the subject of Antarctic botany, Introductory Essay to the Flora Tasmaniae, he became the first scientist to publicly back Charles Darwin's theory of evolution by means of natural selection. Although Thomas H. Huxley is more famously known as "Darwin's bulldog" Hooker played a much larger role in Darwin's personal life. It was Hooker who listened to, read, and criticized Darwin's s first thoughts on the subject of transmutation. Perhaps, even more importantly, it was Hooker, alongside Charles Lyell, who urged Darwin to publish On the Origins of Species, even though Darwin felt it was unfinished and not fully developed.
J. D. Hooker began to attend lectures by his famous botanist father, Sir William Jackson, at the age of seven years old. This undoubtedly had a large influence shaping his career as a botanist, as well as the founder of geographical botany. Much like Darwin, Hooker spent his younger years working as a naturalist on ships which took him around the world. It was while he was upon one such ship, the HMS Erebus, bound for Antarctica, that he first read Darwin's writings. He had been given an early draft of Voyage of the Beagle by the geologist Charles Lyell.
Upon his return from the HMS Erebus Darwin asked Hooker to help him identify some of the botanical material he had collected during his the Beagle voyage which still remained unclassified. They pair became fast friends and continued to consult each other for many years. On January 11, 1844 Darwin first presented his ideas about transmutation to Hooker. Althogh he did have some criticism of the theory, he was largely sympathetic to the idea, and found many of Darwin's thoughts on the subject intriguing.
Some years later in 1858 the naturalist Alfred Russel Wallace sent Darwin his own paper on the subject of evolution. Wallace had composed the paper based upon his own research he had conducted during his time working as a biological specimen collector in Malayasia. Wallace, who was not a part of the upper class like Darwin and Hooker and therefor not part of scientific community of Victorian England, was looking for support from respected an academic in the hope that someone might take his ideas seriously.
Both Darwin and Hooker took Wallace's ideas very seriously. Hooker arranged for Wallace's paper to be presented at the next Linnean Society meeting. However, Hooker also made sure Wallace's paper was accompanied by notes from Darwin that effected demonstrated Darwin had been previously aware of the theory natural selection. After the meeting Hooker instructed Darwin that he needed to put his pen to paper and write the definitive text on the subject of evolution. Darwin did the next best thing. He spent the following months composing an introductory text on the subject which he titled On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.