Dawin's idea, that all species are descended from common ancestors, had been suggested by other thinkers, including Jean Baptiste Lamark, long before Darwin published his book The Origin of Species.
Darwin called the spliting of one species to two the "princile of divergence".
Darwin's evidence fell within four categories: biogeography, palientology, embryology, and morphology.
-What made Darwin's book so remarkable when it appeared, and so influential in the long run, was that it offered a rational explanation oh how evolution must occur.
-The gist of the concept is that small, random, heritable differences among individuals result in differnt chances of survival and reproduction, success for some, death without offspring for others, and that this natural culling leads to significant changes in shape, size, strength, armament, color, biochemistry, and behavior among the decendants.
-His 1859 book On the Origin of Species established evolution by common descent as the dominant scientific explanation of diversification in nature. (http://en.wikipedia.org/wiki/Charles_Darwin)
