e emergence of new species or life forms. First, he stated the obvious, that "under varying conditions organic beings [possess] an infinite diversity in structure, constitution, and habits" (Moore 126). Second, each such organism undergoes a severe "struggle for existence" (126). In adapting to the need to survive in an environment of finite resources, the organism develops characteristics helpful for that purpose which were then passed on through reproduction during which "they will tend to produce offspring similarly situated" (Moore 126). The organism which develops the necessary variations to survive will also tend to be successful in sexual selection and thereby ensure the survival of the species because it will have a competitive advantage in the mating process. Darwin called the mechanism which produced these variations needed to survive natural selection, as opposed to supernatural design (God) or artificial alternatives, such as breeding. He called this "the principle of preservation, or the survival of the fittest" (Wells 167). His view was that organic beings developed such slight variations continuously, but very slowly over time and over generations, not suddenly. Those organic beings which developed such variations successfully among a population of otherwise like beings would eventually become numerous enough to constitute a new surviving species. Those which did not would perish or become extinct.
Descent of Man. In Darwin's view, humans were just one of many life forms which had evolved through natural selection of adaptive variations. The Descent of Man was "a powerful attempt not only to demonstrate the link [of men] with the animal kingdom but to explain how mankind acquired those faculties which were so long regarded as uniquely human" (Bowler 142). Darwin emphasized man's adaptive development of an erect posture which distinguished him from other anthropoids and freed his hands for useful tasks such as tool-m...