In 1859, Charles Darwin published On the Origin of Species, establishing the foundation from which science has uncovered a profound understanding of the world and it's inhabitants. However, there is a common misconception that Darwin's role in evolutionary theory is that he was first to theorize it. In fact, our earliest account of evolution being theorized is in 1809 by a French biologist, Jean-Baptiste Lamarck. Darwin is important for his modernization of the theory, confronting the "why" and "how" questions, and discrediting much of the inaccuracies of Lamarckian evolutionary theory.
Lamarck's theory of evolution was rooted in the Aristotelian scala nature (scale of nature), or the "great chain of being." Greeks theorized there to be a natural hierarchy of organisms and matter, with minerals at the bottom, then plants, animals and finally, gods. Once Christianity adopted the model, gods were replaced with the christian god, and prophets and angels were fixed between humanity and God. What Lamarck theorized is that species evolved within the hierarchy through what was called the transmutation of species. He supposed that all species began at the lowest rung and evolved "up."
Darwinian theory proposed that there was no hierarchy, that no species was intrinsically "better" than another. He contributed the theory of natural selection, which upheld that survival and reproduction are the true measures of "success" in a species, not intelligence and reason, and evolution is necessary for adaptations to changes in the environment or other factors which may thwart survival and reproduction.
The notion of a stratified ranking in which species gradually progress toward superiority implies a consistence in evolutionary change. However, Darwinian theory accounts for the holes in the Lamarckian theory, for instance, why changes are far less frequent in most deep-sea aquatic organisms. They exist in an environment nearly identical to that of their ancestors hundreds of millions of years ago, thus there is little pressure to adapt.
Darwin's theory begot the understanding of the gene as the basic unit of evolution - that more successful genes were passed down generation to generation. Lamarck's theory assumed little variability within species, while Darwin's understood species to have many essential similarities, but still varied in certain traits. Therefore, it is these differences within a species which allow a gradual change through the carrying on of particular traits.
Reference(s):
Dunbar, R. (1998). Grooming, Gossip and the Evolution of Language. Cambridge, MA: Harvard University Press.
