On the Origin of Species
On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, also known as The Origin of Species, is a book first published in 1859 by Charles Darwin. It sets out arguments for the evolution of species in the natural world through the process of natural selection, as opposed to their sudden introduction to the world through an act of special creation by a god. The book is often considered to be the most important in biology. 
"WHEN on board H.M.S. 'Beagle,' as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent. These facts seemed to me to throw some light on the origin of species— that mystery of mysteries"
- — The opening lines of the introduction
Religious Response to the Book
The Origin of Species has been criticised by Bible literalists for its explanation that species change over time rather than being created in their modern form by God.
In 1950, the Catholic Church declared that there was no incompatibility between evolution and Catholicism. The recent popes have favoured a "guided evolution" explanation which combines ideas of creationism with evolution.