Charles Darwin is still widely regarded as one of the most influential scientific thinkers. His work focuses on genetics and biology, but more specifically, evolution. He describes evolution as "natural selection," or the idea that living creature adapt over time based on the most beneficial characteristics. His work, The Descent of Man applies this idea to humanity. The book is one of the first to not use the Bible in relation to creation. Because of the books, many individuals found themselves turning to aethesim, no longer considering themselves a person of faith.