On the Origin of Species more recent study by science historian John van Wyhe has determined that the idea that Darwin delayed publication only dates back to the 1940s, and Darwin's contemporaries thought the time he took was reasonable. Darwin always finished one book before starting another. While he was researching, he told many people about his interest in transmutation without causing outrage. He firmly intended to publish, but it was not until September 1854 that he could work on it full-time. His 1846 estimate that writing his "big book" would take five years proved optimistic. An 1855 paper on the "introduction" of species, written
On the Origin of Species only the last chapter still to write. In September the main title still included ""An essay on the origin of species and varieties"", but Darwin now proposed dropping "varieties". With Murray's persuasion, the title was eventually agreed as "On the Origin of Species", with the title page adding "by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life". In this extended title (and elsewhere in the book) Darwin used the biological term ""races"" interchangeably with ""varieties"", meaning varieties within a species. He used the term broadly, and as well as discussions of "the several