Charles Darwin was an English naturalist who put forth the theory that all living organisms are descended from an earlier common ancestor. He wrote a book, entitled "Origin of the Species", which elaborated on this idea of common ancestry. He felt all organisms descended from a common origin, then branched off with the development of different traits. Some of these traits were useful in helping the organism survive in its environment, while some the traits were not. He called the process that allowed the successful traits to be passed on "natural selection", meaning these traits enabled the organism to survive and thus pass along those traits to it's offspring. This theory has also been called "survival of the fittest". Darwin's ideas were gradually accepted within his lifetime; they are taught in most public and private education class rooms today.