Charles Darwin's On the Origin of Species changed the way we understand the beginnings of life on earth. Darwin's ideas challenged people to think differently, to question long-held beliefs, and to explore a new field of scientific discovery. As a young man, Darwin worked to join the priesthood, but his life took a turn toward science after he joined a government mission to South America and the Pacific. Darwin's work on the trip pushed him to come up with new ideas about life and nature, includ