Charles Darwin is famous for the strong case he made in support of his theory of evolution. He showed how species changed over time, and proposed that all life resulted from evolution. His theory was controversial but eventually caught on with the scientific community.
In Darwin's day, scientists had a number of explanations about how life could change over time. Some believed that creatures changed in large steps; others believed that the behavior of parents affected their offspring. By collecting finches and showing how small changes improved their odds of survival, Darwin presented a compelling case for evolution.
Darwin was not the first person to posit evolution, but he made it his primary area of research for years. While not all of his contemporaries initially accepted his theory, it is now the only scientific framework that explains life on earth.
Not everything Darwin wrote turned out to be true, and the theory of evolution has changed considerably over the years. Scientists still debate the nature of evolution and seek to determine patterns. While some believe that the rate of evolution is fairly consistent, others are proponents of punctuated equilibrium, where most evolution occurs when species face extreme levels of pressure from nature and competition.