It is commonly thought today that the theory of evolution originated from Charles Darwin in the nineteenth century. However, the idea that species mutate over time has been around for a long time in one form or another. Therefore, by Darwins time the idea that species change from one type into another was by no means new, but was rejected by most because the proponents of evolution could not come up with a satisfactory mechanism that would explain this change. But how did Darwin come up with an acceptable theory of evolution, and how did Darwins proposal of natural selection impact the theory of evolution? The answer lies in the study of the works of others, and in the works of Darwin himself, through his theories, his travels and his scientific pioneering. The most influential evolutionary theories prior to Darwin were those of Lamarck and Geoffrey St. Hilaire, developed between 1794 and 1830. Lamarck suggested that species evolve through the use or disuse of particular organs. In the classic example a giraffe that stretches its neck slightly to reach higher leaves will gain in neck length, and this small gain would be passed on to its offspring. (Poirier, McKee, 1999) St. Hilaire, on the other hand suggested that the change was discontinuous, large in magnitude, and occurred at the production of offspring. However, these theories of evolution were based on explanations that offered no demonstrated mechanism. (Bowler, 1990)Darwins theory of evolution differs in that it is based on three easily verified observations. First, individuals within a species vary from one another in morphology, physiology, and behavior. Second, variation is in some part heritable so that variant forms have offspring that resemble them. Third, different variants leave different number of offspring(Wilson, 1999). Darwin than proceeded to elaborate on the mechanism of evolution by suggesting that in the universal struggle for life, nature selects those indi...
