Evolution is often said to be both theory and fact. This statement, or something similar, is frequently seen in biological literature.^{[1][2][3][4][5][6][4][7][4][8][9][10]} The point of this statement is to differentiate the concept of the "fact of evolution", namely the observed changes in populations of organisms over time, with the "theory of evolution", namely the current scientific explanation of how those changes came about. This article is about evolution in biology. ... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... For the trade organisation, see Federation Against Copyright Theft. ... This article is about evolution in biology. ... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ...

The terminology of science

Scientists use many specialized terms, frequently attributing to common words meanings foreign to the layperson. In particular,

• A fact is an observation or a piece of data. Facts can include objective measurements which can be either pieces of verifiable evidence, or the results of an experiment which can be repeated over and over again by different people.^{[11][12][13][14][15][16][17]} For example, the gravitational force can be measured and observed so can therefore be described by scientists as a fact. Every time an apple is dropped and it falls, an observation of gravity is made.

• Theories in science are different from facts. Scientific theories describe the coherent framework into which observable data fit. There have been many theories that attempt to explain the fact of gravity. That is, scientists ask what is gravity, and what causes it. They develop a model to explain gravity, a theory of gravity. Predictions can be made and tested based on this theory. Many explanations of gravity that qualify as a Theory of Gravity have been proposed over the centuries: Aristotle's, Galileo's, Newton's, and now Einstein's.
  In science, a current theory is the theory that has no equally acceptable alternate theory, and has not been falsified. That is, there have been no observations made which contradict it to this point and, indeed, every observation ever made either supports the current theory or at least does not falsify it. Should new observations contradict the current theory, the theory must be revised or a new theory needs to be developed to explain the current findings (see paradigm shift or scientific revolution). Falsification of a theory does not falsify the facts on which it is based.

Confusion of the terms can arise when a single word is used to describe both the observed facts and the theory to explain those facts. The word gravity can be used to refer to the observed facts (i.e the observed attraction of masses) and the theory used to explain it (gravity is the reason why masses attract each other). Thus gravity is both a theory and a fact. For the trade organisation, see Federation Against Copyright Theft. ... In science, the ideal of objectivity is an essential aspect of the scientific method, and is generally considered by the scientific community to come about as a result of strict observance of the scientific method, including the scientists willingness to submit their methods and results to an open debate by... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... For other uses, see Aristotle (disambiguation). ... Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... Einstein redirects here. ... Falsifiability (or refutability or testability) is the logical possibility that an assertion can be shown false by an observation or a physical experiment. ... Paradigm shift is the term first used by Thomas Kuhn in his 1962 book The Structure of Scientific Revolutions to describe a change in basic assumptions within the ruling theory of science. ... This article is about the period or event in history. ...

Scientific terminology applied to evolution

The terms fact and theory can be applied to evolution, just as they are to gravity.^[1] Misuse and misunderstanding of how those terms are applied to evolution have been used to construct arguments disputing the validity of evolution.

In the study of biological species, the facts include fossils and measurements of these fossils. The location of a fossil is an example of a fact (using the scientific meaning of the word fact). In species that rapidly reproduce, for example fruit flies, the process of evolutionary change has been observed in the laboratory.^[18] The observation of fruit fly populations changing character is also an example of a fact, using the scientific meaning of the word fact. So evolution is a fact, at least using the scientific meaning of the word fact. These facts require an explanation, just as the observations of gravity did. Species Drosophila melanogaster Drosophila subobscura Drosophila is a genus of small flies whose members are often called fruit flies or more appropriately vinegar flies, wine flies, pomace flies, grape flies, and picked fruit-flies. ...

In biology, there have been many attempts to explain these observations over the years. Lamarckism, Transmutationism and Orthogenesis were all non-Darwinian theories that attempted to explain the observations of species and fossils and other evidence. However, the explanation for all relevant observations regarding the development of life is called the Theory of Evolution. The theory of evolution is based on a model that explains all the available data and observations. Thus evolution is not only a fact but also a theory, just as gravity is both a fact and a theory. Lamarckism or Lamarckian evolution refers to the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also known as based on heritability of acquired characteristics or soft inheritance). It is named for the French biologist Jean-Baptiste Lamarck, who... Transmutation of species refers to the altering of one species into another. ... Orthogenesis, orthogenetic evolution or autogenesis, is the hypothesis that life has an innate tendency to move in a unilinear fashion due to some internal or external driving force. The hypothesis is based on Essentialism, finalism and cosmic teleology and proposes an intrinsic drive which slowly transforms species. ...

For other uses, see Aristotle (disambiguation). ... Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... Lamarckism or Lamarckian evolution refers to the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also known as based on heritability of acquired characteristics or soft inheritance). It is named for the French biologist Jean-Baptiste Lamarck, who... Transmutation of species refers to the altering of one species into another. ... Orthogenesis, orthogenetic evolution or autogenesis, is the hypothesis that life has an innate tendency to move in a unilinear fashion due to some internal or external driving force. The hypothesis is based on Essentialism, finalism and cosmic teleology and proposes an intrinsic drive which slowly transforms species. ... Sir Isaac Newton FRS (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... Einstein redirects here. ... The modern evolutionary synthesis refers to a set of ideas from several biological specialities that were brought together to form a unified theory of evolution accepted by the great majority of working biologists. ...

Evolution as theory and fact in the literature

This confusion between "fact" and "theory" in the study of evolution was explored in a well-known quote by paleontologist Stephen Jay Gould: Paleontology, palaeontology or palæontology (from Greek: paleo, ancient; ontos, being; and logos, knowledge) is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. ... Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ...

Evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And humans evolved from ape-like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered.^[2]

Similarly, Neil Campbell writes in his 1990 biology textbook, Neil A. Campbell (1946 – 2004) was an American scientist known best for his Biology textbook. ...

Today, nearly all biologists acknowledge that evolution is a fact. The term theory is no longer appropriate except when referring to the various models that attempt to explain how life evolves... it is important to understand that the current questions about how life evolves in no way implies any disagreement over the fact of evolution.^[4]

Biologist Ernst Mayr states, Ernst Mayr Ernst Walter Mayr (July 5, 1904, Kempten, Germany – February 3, 2005, Bedford, Massachusetts U.S.), was one of the 20th centurys leading evolutionary biologists. ...

The basic theory of evolution has been confirmed so completely that most modern biologists consider evolution simply a fact. How else except by the word evolution can we designate the sequence of faunas and floras in precisely dated geological strata? And evolutionary change is also simply a fact owing to the changes in the content of gene pools from generation to generation.^[10]

Biologist Richard Lenski writes, Richard E. Lenski (born August 13, 1956) is an American evolutionary biologist. ...

Scientific understanding requires both facts and theories that can explain those facts in a coherent manner. Evolution, in this context, is both a fact and a theory. It is an incontrovertible fact that organisms have changed, or evolved, during the history of life on Earth. And biologists have identified and investigated mechanisms that can explain the major patterns of change.^[8]

This theme arises over and over again in the biological literature in different guises. Carl Sagan wrote "Evolution is a fact, not a theory".^[9] American zoologist and paleontologist George Simpson, stated that "Darwin...finally and definitely established evolution as a fact."^[19] R. C. Lewontin wrote, "It is time for students of the evolutionary process, especially those who have been misquoted and used by the creationists, to state clearly that evolution is a fact, not theory."^[3] Douglas Futuyama writes in his book, "the statement that organisms have descended with modifications from common ancestors--the historical reality of evolution--is not a theory. It is a fact, as fully as the fact of the earth's revolution about the sun."^[5] H. J. Muller states, "If you like, then, I will grant you that in an absolute sense evolution is not a fact, or rather, that it is no more a fact than that you are hearing or reading these words."^[6] Kenneth R. Miller writes, "evolution is as much a fact as anything we know in science."^[20] Insert non-formatted text here Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer and astrobiologist and a highly successful popularizer of astronomy, astrophysics, and other natural sciences. ... George Gaylord Simpson (June 16, 1902 - October 6, 1984) was an American paleontologist. ... Richard Lewontin Richard Charles Dick Lewontin (born March 29, 1929) is an American evolutionary biologist, geneticist and social commentator. ... Douglas Joel Futuyma (born 1942, New York City) is an American biologist. ... Hermann Joseph Muller (December 21, 1890 – April 5, 1967) was an American geneticist and educator. ... Ken Miller Kenneth R. Miller (born 1948) is a biology professor at Brown University. ...

In spite of all the enthusiasm evident in these excerpts, considerable confusion remains in some circles.^[21][22]

The issue was brought before the courts In 1986, when an amicus curiae brief asking the US Supreme Court to reject a Louisiana state law requiring the teaching of creationism in the case Edwards v. Aguillard was signed by 72 US Nobel Prize winners, 17 state academies of science and 7 other scientific societies. The brief provides a detailed argument which it summarises in the following statement.^[23] Amicus curiae (plural amici curiae) is a legal Latin phrase, literally translated as friend of the court, that refers to a person or entity that is not a party to a case that volunteers to offer information on a point of law or some other aspect of the case to... This article is about the U.S. State. ... Holding Teaching creationism in public schools is unconstitutional because it attempts to advance a particular religion. ...

The Act's unconstitutional purpose is also evident in its requirement that both "creation-science" and "evolution-science" be taught as "theory" and not as "proven scientific fact." To a scientist or a science educator, the distinction between scientific theories and scientific facts is well understood. A "fact" is a property of a natural phenomenon. A "theory" is a naturalistic explanation for a body of facts. That distinction permeates all fields of scientific endeavor. It is no more relevant to discussions of the origin of the universe and life than to any other area of research. By singling out one topic in science – "origins" – for special treatment, the legislature conveys the false message that the prevailing theory of "origins" – evolutionary theory – is less robust and reliable than all other scientific concepts. This misleadingly disparaging treatment of evolution confirms that the Act favors a particular religious belief.

Predictive power

A central tenet in science is that a scientific theory is supposed to have a predictive power, and verification of predictions are seen as an important and necessary support for the theory. The theory of evolution did provide such predictions. Two examples are: A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... The New York Times reported on Einsteins confirmed prediction. ...

• Genetic information must be transmitted in a molecular way that will be almost exact but permit slight changes. Indeed, since this prediction was made, biologists have discovered the existence of DNA, which has a mutation rate of roughly 10⁻⁹ per nucleotide per cell division; this provides just such a mechanism.^[24]

• Some DNA sequences are shared by very different organisms. It has been predicted by the theory of evolution that the differences in such DNA sequences between two organisms should roughly resemble both the biological difference between them according to their anatomy and the time that had passed since these two organisms have separated in the course of evolution, as seen in fossil evidence. The rate of accumulating such changes should be low for some sequences, which code for critical RNA or proteins, and high for others - that code for less critical RNA or proteins; but for every specific sequence, the rate of change should be roughly constant through evolution. These results have indeed been found experimentally. Two examples are DNA sequences coding for rRNA which is highly conserved, and DNA sequences coding for fibrinopeptides (amino acid chains which are discarded during the formation of fibrin), which are highly non-conserved.^[24]

The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... A nucleotide is a chemical compound that consists of 3 portions: a heterocyclic base, a sugar, and one or more phosphate groups. ... This does not adequately cite its references or sources. ... Human heart and lungs, from an older edition of Grays Anatomy. ... For other uses, see Fossil (disambiguation). ... For other uses, see RNA (disambiguation). ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... This article is about the class of chemicals. ... Fibrin is a protein involved in the clotting of blood. ...

Related concepts and terminology

• Speculative or conjectural explanations are called hypotheses. Well-tested explanations are called theories.

• "Theories" are not "true" in science, at least in the regular sense of the word "true". "True" "theories" only are "confirmed to such a degree that it would be perverse to withhold provisional assent." ^[2]

• "Proof" of a theory does not exist in science. Proof only exists in mathematics. Experimental observation of the predictions made by a hypothesis or theory is called validation.

• A scientific law is a concept related to a scientific theory. Very well-established "theories" that rely on a simple principle are often called scientific "laws". For example, it is common to encounter reference to "the law of gravity", "the law of natural selection", or the "laws of evolution."

Look up Hypothesis in Wiktionary, the free dictionary. ... In mathematics, a proof is a demonstration that, assuming certain axioms, some statement is necessarily true. ... For other meanings of mathematics or uses of math and maths, see Mathematics (disambiguation) and Math (disambiguation). ...

See also

• Theory vs. Fact (in Creation-evolution controversy)
• Evolution is just a theory, not a fact (in objections to evolution)
• Misconceptions about evolution (in List of misconceptions)
• Epistemology

... The creation-evolution controversy (also termed the creation vs. ... There have been numerous objections to evolution since alternative evolutionary ideas came to be hotly debated around the start of the nineteenth century. ... There have been numerous objections to evolution since alternative evolutionary ideas came to be hotly debated around the start of the nineteenth century. ... This is a list of uncontroversial, undisputed clarifications to common misconceptions. ... This is a list of uncontroversial, undisputed clarifications to common misconceptions. ... Theory of knowledge redirects here: for other uses, see theory of knowledge (disambiguation) According to Plato, knowledge is a subset of that which is both true and believed Epistemology or theory of knowledge is the branch of philosophy that studies the nature, methods, limitations, and validity of knowledge and belief. ...

Notes

Year 1993 (MCMXCIII) was a common year starting on Friday (link will display full 1993 Gregorian calendar). ... is the 22nd day of the year in the Gregorian calendar. ... talk. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... Insert non-formatted text here Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer and astrobiologist and a highly successful popularizer of astronomy, astrophysics, and other natural sciences. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... is the 242nd day of the year (243rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 291st day of the year (292nd in leap years) in the Gregorian calendar. ... Holding Teaching creationism in public schools is unconstitutional because it attempts to advance a particular religion. ... talk. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ... is the 292nd day of the year (293rd in leap years) in the Gregorian calendar. ... Dr. Bruce Alberts (b. ...

References

• J.P. Franck, et al., "Evolution of a satellite DNA family in tilapia." Annual Meeting Canadian Federation of Biological Societies. Halifax, (1990).
• M. Losseau-Hoebeke, "The biology of four haplochromine species of Lake Kivu (Zaire) with evolutionary implications." Thesis, Dept Ichthyology, Rhodes University, Grahamstown, (1992).

External links

• Not Just a Theory Discredits the assertion that evolution is "just a theory", with an explanation of the meaning of the word 'theory' in a scientific context.
• Parody website satirizing theory and fact statements
• Talk Origins Response to the claim that no examples of speciation have been observed.