We know Charles Darwin for his theory of evolution. However, many of us do not know he was not the first person to propose a theory of evolution. He was not the first naturalist to have proposed a concept of evolution or that species undergo important changes over time. Buffon and other naturalists proposed ideas related to evolution before Darwin.
Darwin’s theory was a selectionist theory of evolution; Lamarck’s was an instructionist theory. Lamarck proposed a mechanism called “the inheritance of acquired characteristics”. He remained unsuccessful at linking his theory to strong scientific evidence. The result was his theory being disapproved scientifically.
Charles Darwin gave the next significant idea in this field. Lamarck proposed the theory that the characteristics acquired by a species can be passed on to the next generation. A significant change came with the publication of Darwin’s theory of evolution some fifty years later. His theory of natural selection became a pivotal point in the history of biological evolution. Still, the missing link in Darwin’s theory was the mechanism of inheritance.
Darwin did not provide any explanation on the generation of new species. According to Lamarck’s theory, environmental changes can give rise to new needs. Based upon these needs some organs can become useful or useless. Depending upon these new needs, new organs can develop and the old ones diminish. According to this theory, acquired characteristics are hereditary.
The voyage of Beagle was the most significant point in the development of Darwin’s theory. It was a five year long expedition to South America and the South Pacific. Darwin read a book in Geology called ‘Principles of Geology’ by Charles Lyell on his voyage. His interest in the study of land forms deepened as he read the book. Geology and Economics had also influenced Darwin’s theory significantly.
He was most impressed by Lyell’s theory. He examined fossils during the voyage in the light of Lyell’s theory. Darwin wrote in his memoir, “ Sir C. Lyell and Dr. Hooker, who both knew of my work – the latter having read the sketch of 1844 – honored me by thinking it advisable to publish, with Mr Wallace’s excellent memoir, some brief extracts from my manuscripts.” Darwin took several important notes during the voyage, the scientific community appraised later. Beagle voyage played the most important role in the development of Darwin’s theory, serving as its background. On the basis of this background, the fundamental ideas related to the theory were formed and evolved to become the acclaimed theory.
Alfred Wallace also supported Darwin’s theory. Apart from Lyell’s book and Alfred Wallace, Darwin’s theory was influenced by several other disciplines and ideas from other notable people. Thomas Malthus’s (well known economist) ideas, had also influenced his theory to a large extent. Malthus’ ideas fascinated Darwin and specifically the idea related to human population and that its growth was faster than food production could sustain, had a profound influence on his theory. Malthus’ ideas gave support to the studies Darwin undertook. It is also believed that Darwin’s idea of the survival of the fittest was based upon Malthus’ ideas.
Darwin’s and Wallace’s ideas are believed to be an extension of uniformitarianism. Uniformitarianism is one of the most important concepts in Geoscience having developed during the 1700’s. The theory suggests that landforms existing on the earth’s surface were not born of catastrophic processes. These ideas find their origin in Scottish geologist James Hutton’s works of 1785. His theory was that earth had a long history. It could be observed and interpreted in terms of the current processes. His ideas faced rejection until Sir Charles Lyell presented evidence to prove Hutton’s ideas. It also repelled the theory of ‘Catastrophism’. Main basis of the theory of evolution is the idea that the diversity of species on earth can be explained best by the uniform modification of genetic traits over time.
One major problem with Darwin’s theory was its lack of a viable theory of heredity. Another problem was the age of earth. Lord Kelvin’s theory regarding earth’s age was that it was around a hundred million years old. However, the process envisioned by Darwin was relatively very slow. So, the given time was insufficient for evolution to have taken place. This problem was resolved with the discovery of radioactivity during late nineteenth century.
The most problematic part of Darwin’s theory was a lack of direct proof to prove that the process had taken place over a very long period of time and was not detected easily in fossil records. Finally, it was in the 1920s, that the first related proof was found in the peppered moth. It showed a rapid shift in allele frequencies due to strong selection pressure. After that several examples appeared proving Darwin’s theory genetically.
Most of the criticism for Darwin’s theory came from religious sources. It was for his theory was against the religious and philosophical views of his time. A debate between evolutionism and creationism had begun with the publication of Darwin’s “Origin of Species”. Michael Behe had sarcastically claimed that cell was a black box to Darwin and its inner functions a mystery. Phillip E Johnson raised his criticism regarding the tautology fallacy of Darwinism. However, in the subsequent years the strength of Darwin’s theory could be proved and the theory revolutionized how evolution had been being understood. Before Darwin’s theory, the species were not considered to be the part of a single family tree. In simpler words, Darwin’s theory had changed the course of science and how evolution on earth was envisioned.