Modern evolutionary synthesis

The modern evolutionary synthesis (often referred to simply as the modern synthesis or the evolutionary synthesis), neo-Darwinian synthesis or neo-Darwinism, generally denotes the combination of Charles Darwin's theory of the evolution of species by natural selection, Gregor Mendel's theory of genetics as the basis for biological inheritance, and mathematical population genetics. Major figures in the development of the modern synthesis include Thomas Hunt Morgan, Ronald Fisher, Theodosius Dobzhansky, J.B.S. Haldane, Sewall Wright, William D. Hamilton, Cyril Darlington, Julian Huxley, Ernst Mayr, George Gaylord Simpson, and G. Ledyard Stebbins. Essentially, the modern synthesis (or neo-Darwinism) introduced the connection between two important discoveries; the units of evolution (genes) with the mechanism of evolution (selection). It also represents a unification of several branches of biology that previously had little in common, particularly genetics, cytology, systematics, botany and paleontology.

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 mechanism of inheritance wasn't discovered in Darwin or Wallace's time, however, so the debate was never settled.

Related Topics:
George John Romanes - Alfred Russel Wallace - Lamarckian - Huxley

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Mendelian genetics was rediscovered in 1900. However, there were differences of opinion as to what was the variation that natural selection acted upon. The biometric school, led by Karl Pearson followed Darwin's idea that small differences were important for evolution. The Mendelian school, led by William Bateson, however, thought that Mendel's work gave an evolutionary mechanism with large differences.

Related Topics:
Mendelian genetics - 1900 - Biometric - Karl Pearson - William Bateson

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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 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.

Related Topics:
T. H. Morgan's - Drosophila

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This issue was partially resolved by Ronald Fisher, who in 1918 produced a paper entititled "The Correlation Between Relatives on the Supposition of Mendelian Inheritance", which showed using a model how continuous variation could be the result of the action of many discrete loci. This is sometimes regarded as the starting point of the synthesis.

Related Topics:
Ronald Fisher - 1918 - The Correlation Between Relatives on the Supposition of Mendelian Inheritance - Loci

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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), G. G. Simpson (paleontology), G. Ledyard Stebbins (botany), C. D. Darlington (cytology) and Julian Huxley soon followed. Huxley coined both evolutionary synthesis and modern synthesis in his semi-popular work Evolution: The Modern Synthesis in 1942.

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