Charles Darwin (1809-1882) started out his career studying medicine and later on theology at Edinburgh University. His father had hoped that he would become a clergyman, but this was not to be. Darwin had developed an interest in beetles, through this interest he was introduced to Reverend Henslow a professor of botany. Henslow was the one who recommended Darwin as a naturalist and companion to Robert FitzRoy, captain of the Beagle.
The voyage of the Beagle lasted for five years. In those five years Darwin studied fossils, animal life, and he also looked at native and colonial cultures. Due to some publicity work on the part of Henslow Darwin had become a celebrity by the time of his return in 1836. Using his new found fame he sought out other naturalist to help him sort out and organize his notes on the different species he had observed. It was not until close to twenty years after his return that he wrote his ground breaking "On the Origin of Species by Means of Natural Selection, or The Preservation of Favored Races in the Struggle for Life", which went on sale in 1859. In it, as the title indicates, is his famous theory of natural selection as evidence for evolution of species over time, which even to this day is a point of contention between certain groups.