Read the following passage given below and Answer the question.

It was, the British naturalist Charles Darwin, who in 1871, first put forward the idea that humans have evolved from apes, in his book, The Descent of Man. Darwin based his hypothesis on his wide-ranging studies of plant and animal life, of different continents and islands of the World, which he carried out during a five-year voyage-from 1831 to 1836-on board the research ship HMS Beagle. On examining the hundreds of species of plants, animals and birds he had seen and collected during the voyage, Darwin could discern small changes in the characters between similar species inhabiting different ecological niches. He summarised his findings in the book, On the Origin of Species by Means of Natural Selection, published in 1859, in which he described how one species could evolve into another more fit to survive in a changed environment, by a process which he called natural selection. (The term 'survival of the fittest' was later used by the English philosopher Herbert spencer.) Human beings, Darwin believed, evolved by a similar process. Even before Darwin, Thomas Henry Huxley in his book, Man's place in Nature, published in 1863, had made a detailed comparison of human and ape anatomy that established the case for close relationship between humans and apes. Huxley suggested that our relationship to the ape is so close that an evolutionary link is inescapable! But, he admitted, it was difficult to predict exactly what the common ancestor might have looked like.

The book in which Darwin describes the process, which he calls "natural selection" was published in the year ________.

1859

The correct answer is 1859.

The passage explicitly states that Darwin summarized his findings on natural selection in a book published in 1859.