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Definition of EVOLUTION
: one of a set of prescribed movements
a: a process of change in a certain direction :unfolding
b: the action or an instance of forming and giving something off :emission
c (1): a process of continuous change from a lower, simpler, or worse to a higher, more complex, or better state :growth(2): a process of gradual and relatively peaceful social, political, and economic advance
a: the historical development of a biological group (as a race or species) :phylogeny
b: a theory that the various types of animals and plants have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations; also: the process described by this theory
: the extraction of a mathematical root
: a process in which the whole universe is a progression of interrelated phenomena
: a process of change in a certain direction <tumor evolution and progression—I. J. Fidler et al>
a: the historical development of a biological group (as a race or species) :phylogenyb: a theory that the various types of animals and plants have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations
Biological theory that animals and plants have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations. It is one of the keystones of modern biological theory. In 1858 Charles Darwin and Alfred Russel Wallace jointly published a paper on evolution. The next year Darwin presented his major treatise On the Origin of Species by Means of Natural Selection, which revolutionized all later biological study. The heart of Darwinian evolution is the mechanism of natural selection. Surviving individuals, which vary (seevariation) in some way that enables them to live longer and reproduce, pass on their advantage to succeeding generations. In 1937 Theodosius Dobzhansky applied Mendelian genetics (seeGregor Mendel) to Darwinian theory, contributing to a new understanding of evolution as the cumulative action of natural selection on small genetic variations in whole populations. Part of the proof of evolution is in the fossil record, which shows a succession of gradually changing forms leading up to those known today. Structural similarities and similarities in embryonic development among living forms also point to common ancestry. Molecular biology (especially the study of genes and proteins) provides the most detailed evidence of evolutionary change. Though the theory of evolution is accepted by nearly the entire scientific community, it has sparked much controversy from Darwin's time to the present; many of the objections have come from religious leaders and thinkers (seecreationism) who believe that elements of the theory conflict with literal interpretations of the Bible. See alsoHugo de Vries, Ernst Haeckel, human evolution, Ernst Mayr, parallel evolution, phylogeny, sociocultural evolution, speciation.