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HISTORY George John Romanes coined the term ''neo-Darwinism'' to refer to the theory of evolution preferred by Alfred Russel Wallace ''et al''. Wallace rejected the Lamarckian idea of inheritance of acquired characteristics, something that Darwin, Huxley ''et al'' wouldn't rule out. The most prominent "neo-Darwinian" of the time after Darwin was August Weismann , who argued that hereditary material, which he called the Germ Plasm , was kept utterly separate from the development of the organism. This was seen by most biologists as an extreme position, however, and variations of neo-Lamarckism, Orthogenesis ("progressive" evolution), and Saltationism (evolution by "jumps" or Mutation s) were discussed as alternatives. In 1900, Mendelian Inheritance was "rediscovered", and was initially seen as supporting a form of "jumping" Evolution . The Biometric School , led by Karl Pearson and Walter Frank Raphael Weldon , argued against it vigorously, stating empirical evidence indicated that variation was continuous in most organisms. The Mendelian school, led by William Bateson , countered that in some cases the Mendelian evidence was indisputable and that future work would reveal its larger truth. Mendelism was taken up by many biologists, even though it was still extremely crude at this early stage. Its relevance to evolution was still hotly debated. A critical link between experimental biology and evolution, as well as between Mendelian genetics, natural selection, and the chromosome theory of inheritance, arose from T. H. Morgan's work with the fruit fly '' Drosophila Melanogaster ''. In 1910, Morgan discovered a mutant fly with solid white eyes (wild-type ''Drosophila'' have red eyes), and found that this condition—though appearing only in males—was inherited precisely as a Mendelian recessive trait. In the subsequent years, he and his colleagues developed the Mendelian-Chromosome theory of inheritance and Morgan and his colleagues published ''The Mechanism of Mendelan Inheritance'' in 1915. By that time, most biologists accepted that genes situated linearly on chromosomes were the primary mechanism of inheritance, although how this could be compatible with natural selection and gradual evolution remained unclear. Morgan's work was so popular that it is considered a hallmark of classical genetics. This issue was partially resolved by . This is sometimes regarded as the starting point of the synthesis, as Fisher was able to provide a rigorous statistical model for Mendelian inheritance, satisfying both the needs (and methods) of the biometric and Mendelian schools. Morgan's student Theodosius Dobzhansky was the first to apply Morgan's chromosome theory and the mathematics of population genetics to natural populations of organisms, in particular '' Drosophila Pseudoobscura ''. His 1937 work ''Genetics and the Origin of Species'' is usually considered the first mature work of neo-Darwinism, and works by Ernst Mayr ('' Systematics And The Origin Of Species '' – systematics), G. G. Simpson ('' Tempo And Mode In Evolution '' – paleontology) , G. Ledyard Stebbins ('' Variation And Evolution In Plants '' – botany), these are considered the four canonical works of the modern synthesis. C. D. Darlington (cytology) and Julian Huxley also wrote on the topic; Huxley coined both evolutionary synthesis and '''modern synthesis''' in his semi-popular work ''Evolution: The Modern Synthesis'' in 1942. TENETS OF THE MODERN SYNTHESIS According to the modern synthesis as established in the 1930s and 1940s , genetic variation in populations arises by chance through Mutation (this is now known to be sometimes caused by mistakes in DNA Replication ) and Recombination (crossing over of homologous Chromosome s during Meiosis ). Evolution consists primarily of changes in the Frequencies Of Alleles between one generation and another as a result of Genetic Drift , Gene Flow and Natural Selection . Speciation occurs gradually when populations are reproductively isolated, e.g. by geographic barriers. FURTHER ADVANCES The modern evolutionary synthesis continued to be developed and refined after the initial establishment in the 1930s and 1940s. The work of W. D. Hamilton , George C. Williams , John Maynard Smith and others led to the development of a Gene-centric View Of Evolution in the 1960s. The synthesis as it exists now has extended the scope of the Darwinian idea of natural selection, specifically to include subsequent scientific discoveries and concepts unknown to Darwin such as DNA and Genetics that allow rigorous, in many cases mathematical, analyses of phenomena such as Kin Selection , Altruism , and Speciation . A particular interpretation of neo-Darwinism most commonly associated with Richard Dawkins asserts that the gene is the only true Unit Of Selection . Dawkins further extended the Darwinian idea to include non-biological systems exhibiting the same type of selective behavior of the 'fittest' such as Meme s in culture. "Increasingly, studies of genes and genomes are indicating that considerable horizontal transfer has occurred between prokaryotes." http://www.pnas.org/cgi/content/abstract/96/7/3801 Horizontal Gene Transfer is called by some "A New Paradigm for Biology " http://www.esalenctr.org/display/confpage.cfm?confid=10&pageid=105&pgtype=1 and emphasised by others as an important factor in "The Hidden Hazards of Genetic Engineering". "While horizontal gene transfer is well-known among bacteria, it is only within the past 10 years that its occurrence has become recognized among higher plants and animals. The scope for horizontal gene transfer is essentially the entire biosphere, with bacteria and viruses serving both as intermediaries for gene trafficking and as reservoirs for gene multiplication and recombination (the process of making new combinations of genetic material)." http://online.sfsu.edu/~rone/GEessays/horizgenetransfer.html SEE ALSO IMPORTANT PUBLICATIONS
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