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evolution
Article Free Pass- Introduction
- General overview
- The science of evolution
- The process of evolution
- Species and speciation
- Patterns and rates of species evolution
- Reconstruction of evolutionary history
- Molecular evolution
- Related
- Contributors & Bibliography
- Year in Review Links
- Introduction
- General overview
- The science of evolution
- The process of evolution
- Species and speciation
- Patterns and rates of species evolution
- Reconstruction of evolutionary history
- Molecular evolution
- Related
- Contributors & Bibliography
- Year in Review Links
evolution, theory in biology postulating that the various types of plants, animals, and other living things on Earth have their origin in other preexisting types and that the distinguishable differences are due to modifications in successive generations. The theory of evolution is one of the fundamental keystones of modern biological theory.
The diversity of the living world is staggering. More than 2 million existing species of organisms have been named and described; many more remain to be discovered—from 10 million to 30 million, according to some estimates. What is impressive is not just the numbers but also the incredible heterogeneity in size, shape, and way of life—from lowly bacteria, measuring less than a thousandth of a millimetre in diameter, to stately sequoias, rising 100 metres (300 feet) above the ground and weighing several thousand tons; from bacteria living in hot springs at temperatures near the boiling point of water to fungi and algae thriving on the ice masses of Antarctica and in saline pools at −23 °C (−9 °F); and from giant tube worms discovered living near hydrothermal vents on the dark ocean floor to spiders and larkspur plants existing on the slopes of Mount Everest more than 6,000 metres (19,700 feet) above sea level.
The virtually infinite variations on life are the fruit of the evolutionary process. All living creatures are related by descent from common ancestors. Humans and other mammals descend from shrewlike creatures that lived more than 150 million years ago; mammals, birds, reptiles, amphibians, and fishes share as ancestors aquatic worms that lived 600 million years ago; and all plants and animals derive from bacteria-like microorganisms that originated more than 3 billion years ago. Biological evolution is a process of descent with modification. Lineages of organisms change through generations; diversity arises because the lineages that descend from common ancestors diverge through time.
The 19th-century English naturalist Charles Darwin argued that organisms come about by evolution, and he provided a scientific explanation, essentially correct but incomplete, of how evolution occurs and why it is that organisms have features—such as wings, eyes, and kidneys—clearly structured to serve specific functions. Natural selection was the fundamental concept in his explanation. Natural selection occurs because individuals having more-useful traits, such as more-acute vision or swifter legs, survive better and produce more progeny than individuals with less-favourable traits. Genetics, a science born in the 20th century, reveals in detail how natural selection works and led to the development of the modern theory of evolution. Beginning in the 1960s, a related scientific discipline, molecular biology, enormously advanced knowledge of biological evolution and made it possible to investigate detailed problems that had seemed completely out of reach only a short time previously—for example, how similar the genes of humans and chimpanzees might be (they differ in about 1–2 percent of the units that make up the genes).
This article discusses evolution as it applies generally to living things. For a discussion of human evolution, see the article human evolution. For a more complete treatment of a discipline that has proved essential to the study of evolution, see the articles genetics, human and heredity. Specific aspects of evolution are discussed in the articles coloration and mimicry. Applications of evolutionary theory to plant and animal breeding are discussed in the articles plant breeding and animal breeding. An overview of the evolution of life as a major characteristic of Earth’s history is given in community ecology: Evolution of the biosphere. A detailed discussion of the life and thought of Charles Darwin is found in the article Darwin, Charles.
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People
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(British naturalist)"/>
(British naturalist)"/> Alfred Russel Wallace (British naturalist)
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(American biologist)"/>
(American biologist)"/> Alfred Sherwood Romer (American biologist)
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(German biologist)"/>
(German biologist)"/> August Weismann (German biologist)
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(British naturalist)"/>
(British naturalist)"/> Charles Darwin (British naturalist)
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(American botanist)"/>
(American botanist)"/> Charles Joseph Chamberlain (American botanist)
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Cyril Dean Darlington (British biologist)
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(American botanist)"/>
(American botanist)"/> Douglas Houghton Campbell (American botanist)
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(American biologist)"/>
(American biologist)"/> Edwin Grant Conklin (American biologist)
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(British physician)"/>
(British physician)"/> Erasmus Darwin (British physician)
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(German embryologist)"/>
(German embryologist)"/> Ernst Haeckel (German embryologist)
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(American biologist)"/>
(American biologist)"/> Ernst Mayr (American biologist)
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Étienne Geoffroy Saint-Hilaire (French naturalist)
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Francisco J. Ayala (American geneticist and biologist)
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Franz Weidenreich (German anthropologist)
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(English botanist)"/>
(English botanist)"/> Frederick Orpen Bower (English botanist)
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George Gaylord Simpson (American paleontologist)
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(French philosopher)"/>
(French philosopher)"/> Henri Bergson (French philosopher)
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Herbert Spencer (British philosopher)
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Hugo de Vries (Dutch botanist and geneticist)
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(British geneticist)"/>
(British geneticist)"/> J.B.S. Haldane (British geneticist)
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(Scottish jurist and anthropologist)"/>
(Scottish jurist and anthropologist)"/> James Burnett, Lord Monboddo (Scottish jurist and anthropologist)
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(American geologist and mineralogist)"/>
(American geologist and mineralogist)"/> James D. Dana (American geologist and mineralogist)
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(French biologist)"/>
(French biologist)"/> Jean-Baptiste Lamarck (French biologist)
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Jean-Baptiste-Julien d’ Omalius d’Halloy (Belgian geologist)
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(American historian)"/>
(American historian)"/> John Fiske (American historian)
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(German anatomist)"/>
(German anatomist)"/> Karl Gegenbaur (German anatomist)
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(British mathematician)"/>
(British mathematician)"/> Karl Pearson (British mathematician)
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(Austrian zoologist)"/>
(Austrian zoologist)"/> Konrad Lorenz (Austrian zoologist)
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Lynn Margulis (American biologist)
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Marjorie Grene (American philosopher)
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Oka Asajirō (Japanese biologist)
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Otto Heinrich Schindewolf (German paleontologist)
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Pierre Dansereau (Canadian plant ecologist)
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Pierre Teilhard de Chardin (French philosopher and paleontologist)
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(British biologist and writer)"/>
(British biologist and writer)"/> Richard Dawkins (British biologist and writer)
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(British philosopher)"/>
(British philosopher)"/> Samuel Alexander (British philosopher)
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(American geneticist)"/>
(American geneticist)"/> Sewall Wright (American geneticist)
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(Scottish anthropologist)"/>
(Scottish anthropologist)"/> Sir Arthur Keith (Scottish anthropologist)
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(Scottish geologist)"/>
(Scottish geologist)"/> Sir Charles Lyell, Baronet (Scottish geologist)
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Sir D’Arcy Wentworth Thompson (Scottish zoologist)
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Sir Edwin Ray Lankester (British zoologist)
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Sir Gavin de Beer (British zoologist)
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Sir John Graham Kerr (British biologist)
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(British biologist)"/>
(British biologist)"/> Sir Julian Huxley (British biologist)
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Sir Patrick Geddes (Scottish biologist and sociologist)
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(British biologist)"/>
(British biologist)"/> T.H. Huxley (British biologist)
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Theodosius Dobzhansky (American scientist)
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(British biologist)"/>
(British biologist)"/> William Bateson (British biologist)
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(Canadian-American paleontologist)"/>
(Canadian-American paleontologist)"/> William Diller Matthew (Canadian-American paleontologist)
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William Donald Hamilton (British naturalist and population geneticist)
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Topics
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(biology and physiology)"/>
(biology and physiology)"/> adaptation (biology and physiology)
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(biology)"/>
(biology)"/> adaptive radiation (biology)
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analogy (evolution)
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antigenic drift (biology)
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antigenic shift (biology)
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Bergmann’s Rule (zoology)
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biogenetic law (biology)
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biology
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climatic adaptation (physical anthropology)
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creative evolution (philosophy)
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(social science)"/>
(social science)"/> cultural evolution (social science)
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Darwinism (biology)
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Devonian extinctions
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Dollo’s law (biology)
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emergence (science)
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end-Triassic extinction
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endangered species
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(biology)"/>
(biology)"/> extinction (biology)
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Gaia hypothesis (Earth science)
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(genetics)"/>
(genetics)"/> heredity (genetics)
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(evolution)"/>
(evolution)"/> homology (evolution)
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human evolution
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(biology)"/>
(biology)"/> industrial melanism (biology)
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K–T extinction
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(biology)"/>
(biology)"/> life (biology)
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missing link (evolutionary theory)
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(biology)"/>
(biology)"/> morphology (biology)
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mosaic evolution
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(genetics)"/>
(genetics)"/> mutation (genetics)
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(biology)"/>
(biology)"/> natural selection (biology)
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neo-Darwinism (biology)
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Ordovician-Silurian extinction
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orthogenesis (biology)
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paedomorphosis (biology)
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parallel evolution (biology)
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Permian extinction
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phylogenetic tree (biology)
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(biology)"/>
(biology)"/> phylogeny (biology)
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(microbiology)"/>
(microbiology)"/> pleomorphism (microbiology)
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polymorphism (biology)
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polyploidy (genetics)
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runaway selection hypothesis (biology)
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(biology)"/>
(biology)"/> selection (biology)
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selection coefficient (genetics)
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(biology)"/>
(biology)"/> sexual dimorphism (biology)
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(biology)"/>
(biology)"/> sexual selection (biology)
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social Darwinism
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(biology)"/>
(biology)"/> speciation (biology)
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variation (biology)
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General overview
The evidence for evolution
Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms. Since Darwin’s time, the evidence from these sources has become considerably stronger and more comprehensive, while biological disciplines that emerged more recently—genetics, biochemistry, physiology, ecology, animal behaviour (ethology), and especially molecular biology—have supplied powerful additional evidence and detailed confirmation. The amount of information about evolutionary history stored in the DNA and proteins of living things is virtually unlimited; scientists can reconstruct any detail of the evolutionary history of life by investing sufficient time and laboratory resources.
Evolutionists no longer are concerned with obtaining evidence to support the fact of evolution but rather are concerned with what sorts of knowledge can be obtained from different sources of evidence. The following sections identify the most productive of these sources and illustrate the types of information they have provided.
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