This text is for the following questions 27 to 30

Charles Robert Darwin was an English scientist, who proposed and provided evidence for the scientific theory that all species have evolved through natural selection. This theory became widely accepted by the scientific community in the 1930s, and now become the basic of modern evolutionary theory.

Darwin developed his interest in natural history at Edinburgh University while studying first medicine, then theology. His five-year voyage on the Beagle established his as a geologist whose observations and theories supported Charles Lyell's uniformitarian ideas, and publication of his journal of the voyage made him famous as a popular author.

His study on the geographical distribution of wildlife that he collected during the voyage, resulting his theory of natural selection in 1838. Having seen other being attacked for similar ideas, he confided only to his closest friends and continued his research. In 1858, Alfred Russel Wallace sent him an essay describing a similar theory, causing the two to publish their early theories in a joint publication. In 1859 He published his famous book, the Origin of Species.

What initiated Darwin's theory of natural selection?