He first started thinking about this in 1838, but it took a full twenty years before his ideas became public. By 1844 he was able to write a draft of the main ideas in his notebook. Historians think that he did not talk about his theory because he was afraid of public criticism. He knew his theory, which did not discuss religion, raised questions about the literal truth of the Book of Genesis. Whatever the reason, he did not publish his theory in a book until 1859. In 1858 he heard that another biologist, Alfred Russel Wallace, had the same ideas about natural selection. Darwin and Wallace's ideas were first published in the "Journal of the Linnaean Society" in London, 1858. Then, Darwin published his book the next year. The name of the book was "On the Origin of Species by means of Natural Selection, or the preservation of favoured races in the struggle for life". This is usually called "The Origin of Species".