Darwin actually moved towards evolution by the idea of humans descended from apes because he had such an arrogant prejudiced view of native people he met in South America
Science can be distorted by our prejudices, but it this case his prejudices made it easier for him to accept a radical idea

This led him to Thomas Malthus, Essay on the Principle of Population

• argues that population always grows faster than the environment can sustain so there will always be competition for resources
• Malthus argues against welfare for the poor because it is inevitable that there will not be enough to go around and some people will starve to death (if you give them food they will just reproduce and there will be more excess people who will starve to death)
• Laissez fair capitalism: the government should not interfere with the market to help people
  
• Darwin took from this the idea of competition for survival, which he called natural selection
• population is going to grow until it exceeds the food supply
• if there isn't enough food to go around who is going to survive
• the individuals best adapted to the environment are more likely to survive and breed
• the characteristics most common in the population will shift to fit the environment
• can this gradual change eventually result in different species?--this was hard to prove
  

Now he had a mechanism for evolution--the best adapted individuals survive and reproduce, creating gradual change (the other problem is where does the variation come from).  This was immediately parallel to selective breeding by farmers and hobbyists, which Darwin had a lot of experience with

Darwin saw this as incompatible with Christianity because the cruel competition for survival didn't fit his idea of a benevolent God (not because it contradicted the Bible--he didn't expect people to take the Bible literally)
The theory of the best individuals win fit the world of the British Empire he lived in

Darwin did not publish his idea of evolution for 20 years, fearing a negative reaction both on scientific and religious grounds

• in 1858 he received a manuscript by Alfred Russel Wallace with the same essential theory
• in what way was the time right that two people would independently come up with the same idea?
  
• Darwin did pass Wallace's manuscript on to Lyell, as he had been asked
• Wallace's article was published along with two Darwin had written but not published earlier
• who gets credit?  usually the one who published first but Darwin got credit for having the idea for the mechanism of evolution, and also he was the more prominent person
  
• Darwin's book On the Origin of Species was published the next year

what are the religious issues about evolution

• disproves that God directly created plants, animals and humans
• in their perfect form, unchanging
• evolution is more random, not organized by God (some scientists see a more subtle organization by God)
  
• if a good God created this world, how could it be so violent and cruel?
• contradicts the literal interpretation of the 6 days of creation in Genesis (wasn't a common concern until the 20th century)
  
• lowers our status as humans (where does the soul come in?)

From a sermon at Peace Church Clemson, part of the United Church of Christ, for Science Sunday:

• deep human questions are how did the world begin and what does it mean?
• early religions answered that question by grand stories of how the world came to be the way it is, with answers to why and what does it mean woven into those stories
  
• then along came science and gave different answers to the how questions
• but what we need from religion is not an explanation of how, but an explanation of why, and what does it mean?
• the soul is not a scientific thing, it is a spiritual thing