Evolution was not a new idea. The Greeks speculated on it. In the century before Darwin many different evolutionary theories were proposed, among them notable efforts by Buffon, Lamarck, and Goethe. Their common thread was the concept that the succession of biological changes in geological time represented a fact, if not a natural law. The stumbling block was for all of them, as it had been for Cuvier, the concept of fixed species, which clashed with the vision of a distant past populated with races of plants and animals now extinct. It became evident that the idea of fixed species could not explain this. What was needed was a theory which could account for both permanence and impermanence in the natural world. This Charles Darwin supplied. [excerpt