The Contributions Of Darwin And Darwin's Theory Of Evolution

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Theories of evolution started before Darwin’s specific one by natural selection. The most prominent and perhaps influential on Darwin was Lamarck’s theory of “evolution by willing”, or that physical changes during an animal’s lifetime would be passed to offspring, in that it laid the foundation for his more developed explanation for evolution (Mayr, 1982). Darwin believed in evolution several before developing his theory of natural selection, he objected to Lamarck’s theory due to the lack of evidence of some mechanism from this process. He eventually realized that individual differences were key, he learned this from animal breeders and artificial selection because breeders would select individuals with positive traits they desired to breed …show more content…
During Darwin’s time the prevailing theory was blended inheritance by which two parent’s traits would meet in the middle in the offspring however many people during the time period, including Darwin, found flaws with this reasoning for example that it would eventually lead to all organisms being the same. Though Mendel’s work on genetics would have probably offered a good solution it was not until the early 20th century that his work was rediscovered and then combined with Darwin’s theory of natural selection into the Evolutionary Synthesis model. This theory refocuses natural selection from the individual to the gene, this replaced the model of the time; intelligent design, with one that predicted all phenotypes were caused by genes and that natural selection increased or decreased frequency depending on how genes alone affected fitness. This view was very restrictive as it only looked at one level for selection to act on, one level responsible for all different phenotypes, and one level responsible for all variation or as Johnston and Gottlieb (1990) put it “[Evolutionary Synthesis] treats phenotypic change solely as the outcome of genetic …show more content…
The model only allowed mutation and recombination as a cause for variability in a population while we now know “varying the early experiences of young animals alters their behavioral phenotype into adulthood” (Gottlieb 2002). Further the view that gene was the totally responsible for trait expression ignores how many genes animals share in common while development of them is what really creates the large difference, at the same time some there is no link between morphological complexity and the number of genes. These issues with the Evolutionary Synthesis model provided evidence that reductionist view needed to be changed to a more holistic one as the evidence provided demonstrated the genes could not be the only level responsible for phenotypic expression. At the same time the Evolutionary Synthesis theory only look at the effect that the environment had on the individual, however bidirectional influences demonstrate that all levels of construction matter and work to influence each other (Gottlieb 2007). This means that the predetermined epigenesis which is supported by Evolutionary Synthesis cannot be correct, multiple studies have shown that environmental factors indeed influence an alteration in expression or protein synthesis, or phenotypes (Gottlieb 2007). The resulting conclusion is that the deterministic attitude towards genes and their influence on evolution and phenotype had

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