There are plenty of books, magazine articles, as well as online blogs about Charles Darwin’s work and these do great justice to Darwin’s revolutionary ideas and his theories are taught in textbooks in high school biology classes and university courses that it can be hard to appreciate the genius that Darwin was gifted with in arriving at the conclusion that life evolves through natural selection.
Rarely do you hear the detailed steps by which Darwin was lead to his revolutionary idea. The story of course is that Darwin conceived of his theory of evolution when serving as a naturalist aboard the HMS Beagle and after getting his chance to see the wildlife of South America and the Galapagos firsthand. Darwin came up with his theory of natural selection after his voyage and he developed his theory 20 years prior to publication of The Origin of Species. Of course, there is way more to this story and the genesis of Darwin’s revolutionary idea began when he joined the Beagle. While aboard the Beagle, Darwin had the skills as naturalists but he was also interested in geology and he had two copies of a three volume work by Scottish geologists Charles Lyell called The Principle of Geology. While studying the two volumes, there was this one principle in geology that had a major impact on Darwin’s thinking, that was so profound that it influenced his evolutionary views and has become part and parcel of evolutionary theory even today. Just what was this geological principle that so influenced Darwin? It is a principle with a rather long name and that is the principle of uniformitarianism.
What is the principle of uniformitaranism? Basically, it says that for all the geological processes that are occurring today such as sedimentation for example, these kinds of processes are occurring now as they have been occurring in the past and will do so in the future. For example, every landscape that has mountains and valleys were formed by the slow accumulation of sediment upon sediment layer which slowly, in a time span of tens of millions of years, began to slowly lift up while being slowly eroded by ice and wind as in the case for mountains while valleys are usually formed by rivers slowly eroding the ground between mountains. All of these processes were occurring in the past and will do so in the future, which means that the drama of evolving landscapes in a slow and gradual process, where in the distant past where there was once flat plain later became mountains and where there was a rive in between gentle hills later became vast valleys, all requiring vast amounts of time.
What does this have to do with Darwin’s theory of evolution? According to Darwin, evolution or as Darwin originally called it “descent with modification”, evolution is a slow and gradual process where it would take millions upon millions of years for a population to evolve into many species whether it is animal, plant, or fungus. Even before Darwin wrote extensively about evolution, Darwin knew that every geological feature such as mountains take time to form the same geological processes that have occurred in the past and to form mountains also takes millions of years or more. If mountains and continents rise and fall slowly through vast stretches of time, then considering that life is present in the past as well as in the present then in regards to all of the diversity of life, if according to Darwin evolve by natural selection, then evolution would have to be a slow and gradual process and this was the conclusion that Darwin came to for the evolution of life is intimately tied to the evolution of the earth for all the environments of earth can end up selecting each fit individual for every population, which is part of natural selection and with natural selection as that which the environments, where in fact there are really a variety of environments such as hot desert, cold tundra, and wet rainforest as examples for these kinds of environments form separately as the earth change through uniformitarianism and this will determine whether species evolve into various new species to adapt to the changing environment or else go extinct if unable to do so.
Charles Darwin was a colleague of Lyell and collaborated with him up until the publication of The Origin of Species and Darwin ( 1859) while he stated that evolution by natural selection is what creates adaptations which eventually results in the diversity of species, it is a slow process, an inevitable consequence of uniformitarianism and Darwin gives Lyell credit for his evolutionary views “”I am well aware that this doctrine of natural selection, exemplified in the above imaginary instances, is open to the same objections which were at first urged against Sir Charles Lyell’s noble view on “the modern change of the earth, as illustrative of geology’; but we now seldom hear the action, for instances of the coast wave ass, called a trifling and significant cause… Natural selection can act only by the preservation and accumulation of infinitesimally small inherited modifications, each profitable to the preserved beings, and as modern geology has almost banished such views as the excavation of a great valley by a single diluvial wave, so will natural selection.” (pg. 74). Lyell, himself, never accepted Darwin’s hypothesis of natural selection, but regardless, and through Darwin’s genius, he was the only scientists to use a principle that was originally outside of biology which was uniformitarianism and it was through uniformatarinism that lead to Darwin’s view of evolution with natural selection as the mechanism that results in adaptation so in a way, natural selection became a consequence of that one principle of geology that had much of impact on Darwin which through the Modern Synthesis proved Darwin right.
Darwin, C. (1859) On the Origin of Species By Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. London, England: Murray London
Gould, S.J (2002) The Structure of Evolutionary Theory . Harvard, MA : Harvard University Press Belknap
Martinez, A (27 January, 2016). The Modern Synthesis and Evolutionary Biology. [Web log post]. Retrieved from http://unityoflifeblog.com/the-modern-synthesis-of-evolutionary-biology/
Zimmer, C (2001) Evolution: The Triumph of an Idea. New York, NY: Harper Collins
Michael Rehfeldt https://www.flickr.com/photos/ipjmike/2945619179/in/photolist-5ui4Xz-9v3KxN-rSBnr-5uiJLc-6seyzM CC BY 2.0