Many scientists and philosophers of science have described evolution as fact and theorya phrase which was used as the title of an article by paleontologist Stephen Jay Gould in He describes fact in science as meaning How does radioactive hookup support evolutionnot absolute certainty but "confirmed to such a degree that it would be perverse to withhold provisional assent".
A scientific theory is a well-substantiated explanation of such facts. The facts of evolution come from observational evidence of current processes, from imperfections in organisms recording historical common descentand from transitions in the fossil record. Theories of evolution provide a provisional explanation for these facts.
Each of the words "evolution", "fact" and "theory" has several meanings in different contexts. Evolution means change over time, as in stellar evolution. In biology it refers to observed changes in organisms, to How does radioactive hookup support evolution descent from a common ancestor, and at a technical level to a change in gene frequency over time; it can also refer to explanatory theories such as Charles Darwin 's theory of natural selection which explain the mechanisms of evolution.
To a scientist, fact can describe a repeatable observation that all can agree on; it can refer to something that is so well established that nobody in a community disagrees with it; and it can also refer to the truth or falsity of a proposition.
To the public, theory can mean an opinion or conjecture e. With this number of choices, people can often talk past each other, and meanings become the subject of linguistic analysis. Evidence for evolution continues to be accumulated and tested.
The scientific literature includes statements by evolutionary biologists and philosophers of science demonstrating some of the different perspectives on evolution as fact and theory.
Evolution has been described as "fact and theory"; "fact, not theory"; "only a theory, not a fact"; "multiple theories, not fact"; and "neither fact, nor theory. Professor of biology Jerry Coyne sums up biological evolution succinctly:. This shows the breadth and scope of the issue, incorporating the scientific fields of zoologybotanygeneticsgeologyand paleontologyamong many others.
But the central core of evolution is generally defined as changes in trait or gene frequency in a population of organisms from one generation to the next. How does radioactive hookup support evolution selection is only one of several mechanisms in the theory of evolutionary change that explains how organisms historically adapt to changing environments.
The principles of heredity were re-discovered inafter Darwin's death, in Gregor Mendel 's research on the inheritance of simple trait variations in peas. According to Douglas J. The word evolution in a broad sense refers to processes of change, from stellar "How does radioactive hookup support evolution" to changes in language.
In biology, the meaning is more specific: Individual organisms do not evolve in their lifetimes, but variations in the genes they inherit can become more or less common in the population of organisms. Any changes during the lifetime of organisms which are not inherited by their offspring are not part of biological evolution. To Keith Stewart Thomsonthe word evolution has at least three distinct meanings: Natural selection provides the outline of an explanatory theory.
Biologists consider it to be a scientific fact that evolution has occurred in that modern organisms differ from past forms, and evolution is still occurring with discernible differences between organisms and their descendants.
There is such strong quantitative support for the second that scientists regard common descent as being as factual as the understanding that in the Solar System the Earth orbits the Sun, although the examination of the fundamentals of these processes is still in progress. There are several theories about the mechanisms of evolution, and there are still active debates about specific mechanisms.
There is a fourth meaning for the word evolution that is not used by biologists today. Inthe philosopher Herbert Spencer defined it as "change from the homogeneous to the heterogeneous.
Fact is often used by scientists to refer to experimental or empirical data or objective verifiable observations. In the sense that evolution is overwhelmingly validated by How does radioactive hookup support evolution evidence, it How does radioactive hookup support evolution a fact. It is frequently said to be a fact in the same way as the Earth's revolution around the Sun is a fact. The National Academy of Sciences U. Stephen Jay Gould also points out that "Darwin continually emphasized the difference between his two great and separate accomplishments: Scientists continue to argue about particular explanations or mechanisms at work in specific instances of evolution — but the fact that evolution has occurred, and is still occurring, is undisputed.
A common misconception is that evolution cannot be reliably observed because it all happened millions of years ago and the science therefore is not dependent on facts in the initial sense above. However, both Darwin and Alfred Russel Wallacethe co-founders of the theory, and all subsequent biologists depend primarily on observations of living organisms; Darwin concentrated largely on the breeding of domesticated animals whereas Wallace started from the biogeographical distribution of species in the Amazon and Malay Archipelago.
In the early twentieth century, population genetics had centre stage, and more recently DNA has become the main focus of observation and experimentation.
Philosophers of science argue that we do not know mind-independent empirical truths with absolute certainty: In this sense all facts are provisional. The scientific definition of the word "theory" is different from the definition of the word in colloquial use. In the vernacular, "theory" can refer to guesswork, a simple conjecturean opinionor a speculation that does not have to be based on facts and need not be framed for making testable predictions. In science, however, the meaning of theory is more rigorous.
A How does radioactive hookup support evolution theory is "a well-substantiated explanation of some aspect of the natural world that can incorporate facts, lawsinferences, and tested hypotheses.
In the case of evolution through natural selection, Darwin conceived the hypothesis aroundand made a first draft of the concept three years later in He discussed this widely with many of his intellectual companions, and conducted further research in the background to his other writings and work.
After years of development, he finally published his evidence and theory in On the Origin of Species in The "theory of evolution" is actually a network of theories that created the research program of biology.
Darwin, for example, proposed five separate theories in his original formulation, which included mechanistic explanations for:. Since Darwin, evolution has become a well-supported body of interconnected statements that explains numerous empirical observations in the natural world. Evolutionary theories continue to generate testable predictions and explanations about living and fossilized organisms.
Phylogenetic theory is an example of evolutionary theory. It is based on the evolutionary premise of an ancestral descendant sequence of genes, populations, or species.
Individuals that evolve are linked together through historical and genealogical ties. Evolutionary trees are hypotheses that are inferred through the practice of phylogenetic theory.
They depict relations among individuals that can speciate and diverge from one another. The evolutionary process of speciation creates groups that are linked by a common ancestor and all its descendants. Species inherit traits, which are then passed on to descendants.
Evolutionary biologists use systematic methods and test phylogenetic theory to observe and explain changes in and among species over time. These methods include the collection, measurement, observation, and mapping of traits onto evolutionary trees. Phylogenetic theory is used to test the independent distributions of traits and their various forms to provide explanations of observed patterns in relation to their evolutionary history and biology.
The following sections provide specific quotable references from evolutionary biologists and philosophers of science demonstrating some of the different perspectives on evolution as fact and theory.
Other commentators — focusing on the changes in species over generations and in some cases common ancestry — have stressed, in order to emphasize the weight of supporting evidence, that evolution is a fact, arguing that the use of the term "theory" is not useful:.
Evolutionary biologist Kirk J.
Fitzhugh  writes that scientists must be cautious to "carefully and correctly" describe the nature of scientific investigation at a time when evolutionary biology is under attack from creationists and proponents of intelligent design.
Fitzhugh writes that while facts are states of being in nature, theories represent efforts to connect those states of being by How does radioactive hookup support evolution relationships:. Theories are concepts stating cause—effect relations. Regardless of one's certainty as to the utility of a theory to provide understanding, it would be epistemically incorrect to assert any theory as also being a fact, given that theories are not objects to be discerned by their state of being.
Fitzhugh recognizes that the "theory" versus "fact" debate is one of semantics.
He nevertheless contends that referring to evolution as a "fact" is technically incorrect How does radioactive hookup support evolution distracts from the primary "goal of science, which is to continually acquire causal understanding through the critical evaluation of our theories and hypotheses.
Robertson writing for National Science Teachers Association writes, "I have heard too many scientists claim that evolution is a fact, often How does radioactive hookup support evolution retort to the claim that it is just a theory. Rather than claiming so, I think scientists would be better served to agree that evolution is a theory and then proceed to explain what a theory is -- a coherent explanation that undergoes constant testing and often revision over a period of time.
Graham BellSelection: The Mechanism of Evolution . From Wikipedia, the free encyclopedia. A discussion of the meaning and usage of the terms evolution, fact and theory. Introduction to evolution Evidence of evolution Common descent Evidence of common descent. History of evolutionary theory. Applications of evolution Biosocial criminology Ecological genetics Evolutionary aesthetics Evolutionary anthropology Evolutionary computation Evolutionary ecology Evolutionary economics Evolutionary epistemology Evolutionary ethics Evolutionary game theory Evolutionary linguistics Evolutionary medicine Evolutionary neuroscience Evolutionary physiology Evolutionary psychology Experimental evolution Phylogenetics Paleontology Selective breeding Speciation experiments Sociobiology Systematics Universal Darwinism.