Charles Robert Darwin (12 February 1809 – 19 April 1882) was the 19th Century Scientist who proposed the Theory of Evolution. He was grandson to the major 18th Century thinker Erasmus Darwin. Charles Darwin started life as a Christian and studied Divinity at Cambridge University, although he had a passion for natural history which later brought him to see that religion simply isn’t needed to explain life.
The Voyages of the Beagle
The event which changed the course of Darwin’s life happened when he joined the Voyage of the Beagle to study the natural history of the places the ship visited. During the voyage Darwin read, Lyell's "Principles of Geology" which gave good evidence that the Earth is millions of years old rather than a recent creation. Darwin’s own observations confirmed this. What Darwin saw did not seem consistent with a purposeful benevolent creator. When the Beagle studied the Galapagos Islands Darwin noted that the finches, mockingbirds and tortoises varied from island to island. Later he came to see that these animals had evolved differently on different islands.
Developing the Theory of Evolution
Darwin read Malthus and developed the theory of natural selection. Plants and animals that are well adapted to their environment survive and reproduce better. The features that helped them survive are passed on to future generations. Slowly a whole species changes. And nobody needs God.
Raised a Christian of the Unitarian Universalist denomination, Darwin gradually lost his faith, and some people like to portray Darwin as anti-religion or anti-Christian. Although it is true that he stopped attending church in later life, he did remain active within it helping the church raise funds for Christian charity. Darwin's biggest issue with his beliefs was the effect it might have on his wife, who was very religious.
Race and slavery
Charles Darwin felt kindly towards black people and considered enslaving them an abomination.
I have watched how steadily the general feeling, as shown at elections, has been rising against Slavery. What a proud thing for England, if she is the first European nation which utterly abolish is it. I was told before leaving England, that after living in slave countries: all my options would be altered; the only alteration I am aware of is forming a much higher estimate of the Negros character. It is impossible to see a negro & not feel kindly toward him; such cheerful, open honest expressions & such fine muscular bodies 
During his travels Darwin was an eyewitness to mistratement of slaves. He thought slavery was utterly cruel and indefensible.
Christian conservatives still get exercised about Darwin because he raised the possibility that the existence of God isn't required to explain the multitude of species that exist on Earth today. The thought that humans descended from a common ancestor to the apes drives them nuts and makes them act like apes. So they come up with very odd theories such as the belief that every animal in existence today descended from animals on board Noah's Ark. Yup, they believe in fairy tales.
Darwin traveled around the world on a ship called "The Beagle", and observed phenomena that led to his formation of the Theory of Evolution. Conservatives go to church and believe that this is proof that there is a God who created the Earth and all life on it in 6 days!