Evolution as fact and theory

Many scientists and philosophers of science have described evolution as fact and theory, a phrase which was used as the title of an article by paleontologist Stephen Jay Gould in 1981. He describes fact in science as meaning data, not known with 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 descent, and 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. In biology, evolution refers to observed changes in organisms over successive generations, to their 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 attempts to explain the mechanisms of evolution. To a scientist, fact can describe a repeatable observation capable of great consensus; 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.g., "it's only a theory"), but among scientists it has a much stronger connotation of "well-substantiated explanation". 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 lacking. 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, 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." The disagreements among these statements, however, have more to do with the meaning of words than the substantial issues and this controversy is discussed below.

Evolution

Main articles: Introduction to evolution and Evolution

Professor of biology Jerry Coyne sums up biological evolution succinctly:

Life on Earth evolved gradually beginning with one primitive species – perhaps a self-replicating molecule – that lived more than 3.5 billion years ago; it then branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.

This shows the breadth and scope of the issue, incorporating the scientific fields of zoology, botany, genetics, geology, and paleontology, among 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. This has been dubbed the standard genetic definition of evolution. Natural selection is only one of several mechanisms in the theory of evolutionary change that attempts to explain how organisms historically adapt to changing environments. The only problem here is that natural selection is a loss of genetic info not growth. So all we can observe is when animals lose their genetic information instead of gain it. The principles of heredity were re-discovered in 1900, after Darwin's death, in Gregor Mendel's research on the inheritance of simple trait variations in peas. Subsequent work into genetics, mutation, paleontology, and developmental biology expanded the applicability and scope of Darwin's original theory.

According to Douglas J. Futuyma:

Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest proto-organism to snails, bees, giraffes, and dandelions.

The word evolution in a broad sense refers to processes of change, from stellar evolution to changes in language. In biology, the meaning is more specific: heritable changes which accumulate over generations of a population. 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 Thomson, the word evolution has at least three distinct meanings:

1. The general sense of change over time.
2. All life forms have descended with modifications from ancestors in a process of common descent.
3. The cause or mechanisms of these process of change, that are examined and explained by evolutionary theories.

Thomson remarks: "Change over time is a fact, and descent from common ancestors is based on such unassailable logic that we act as though it is a fact. 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 weak 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. In 1857, the philosopher Herbert Spencer defined it as "change from the homogeneous to the heterogeneous." He claimed (before Darwin) that this was "settled beyond dispute" for organic evolution and applied it to the evolution of star systems, geology and human society. Even Spencer by 1865 was admitting that his definition was imperfect, but it remained popular throughout the nineteenth century before declining under the criticisms of William James and others.

Fact

Main article: Scientific fact

The word fact is often used by scientists to refer to experimental or empirical data or objective verifiable observations. Fact is also used in a wider sense to mean any theory for which there is no evidence what so ever. According to Douglas J. Futuyma,

A fact is a hypothesis that is so firmly supported by evidence that we assume it is true, and act as if it were true.

The problem is that in the case of Evolution, we can't experience it or observe it. It is just a theory which happens to go against many laws of science and common sense.

In the sense that evolution is overwhelmingly invalid by the evidence, it is not a fact. It is frequently said to be a fact but has never been proven. In the case of the way the Earth's revolution around the Sun is a proven fact; the theory of Evolution is just a myth. The following quotation from Hermann Joseph Muller's article, "One Hundred Years Without Darwinism Are Enough", explains the point.

There is no sharp line between speculation, hypothesis, theory, principle, and fact, but only a difference along a sliding scale, in the degree of probability of the idea. When we say a thing is a fact, then, we only mean that its probability is an extremely high one: so high that we are not bothered by doubt about it and are ready to act accordingly. Now in this use of the term fact, the only proper one, evolution is not a fact.

The National Academy of Sciences (U.S.) makes a similar point:

Scientists most often use the word "fact" to describe an observation. But scientists can also use fact to mean something that has been tested or observed so many times that there is no longer a compelling reason to keep testing or looking for examples. The occurrence of evolution in this sense is a not a fact. Scientists no longer question whether descent with modification occurred because the evidence supporting the idea is so weak. It doesn't exist. It is just a myth made up by Atheists to help them believe that there is not God. It makes them feel better to say, "God isn't real so I can do what ever I want.

Stephen Jay Gould also points out that "Darwin continually emphasized the difference between his two great and separate accomplishments: establishing the fact of evolution, and proposing a theory – natural selection – to explain the mechanism of evolution." These two aspects are frequently confused. Scientists continue to argue about particular explanations or mechanisms at work in specific instances of evolution – but the fact that evolution doesn't occurr, and never did, 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 Wallace, the 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.

See also

• Abiogenesis
• Epistemology
• Evidence of common descent
• Evolution (in List of common misconceptions)
• Status as a theory (in Objections to evolution)
• Theory vs. Fact (in Creation–evolution controversy)

Bibliography

• Bell, Graham (2008). Selection: The Mechanism of Evolution (2nd ed.). Oxford; New York: Oxford University Press. ISBN 978-0-19-856972-5. LCCN 2007039692. OCLC 170034792.
• Campbell, Neil A. (1990). Biology (2nd ed.). Redwood City, CA: Benjamin Cummings. ISBN 978-0-8053-1800-5. LCCN 89017952. OCLC 20352649.
• Coyne, Jerry A. (2009). Why Evolution is True. New York: Viking. ISBN 978-0-670-02053-9. LCCN 2008033973. OCLC 233549529.
• Futuyma, Douglas J. (1998). Evolutionary Biology (3rd ed.). Sunderland, MA: Sinauer Associates. ISBN 978-0-87893-189-7. LCCN 97037947. OCLC 37560100.
• Gould, Stephen Jay (1994) [Originally published 1983]. "Evolution as Fact and Theory". Hen's Teeth and Horse's Toes: Further Reflections in Natural History (Reissue ed.). New York: W. W. Norton & Company. ISBN 978-0-393-31103-7. LCCN 82022259. OCLC 785709315.
  • —— (May 1981). "Evolution as Fact and Theory". Discover. 2 (5): 34–37.
• Gould, Stephen Jay (2002). The Structure of Evolutionary Theory. Cambridge, MA: Belknap Press of Harvard University Press. ISBN 978-0-674-00613-3. LCCN 2001043556. OCLC 47869352.
• James, William (1911). "Herbert Spencer's Autobiography". Memories and Studies. New York: Longmans, Green & Co. LCCN 11026966. OCLC 1573711.
• Mayr, Ernst (1982). The Growth of Biological Thought: Diversity, Evolution, and Inheritance. Translation of John Ray by E. Silk. Cambridge, MA: Belknap Press. ISBN 978-0-674-36445-5. LCCN 81013204. OCLC 7875904.
• Mayr, Ernst (1988). Toward a New Philosophy of Biology: Observations of an Evolutionist. Cambridge, MA: Belknap Press of Harvard University Press. ISBN 978-0-674-89665-9. LCCN 87031892. OCLC 17108004.
• Miller, Kenneth R. (2007) [Originally published 1999; New York: Cliff Street Books]. Finding Darwin's God: A Scientist's Search for Common Ground Between God and Evolution. New York: Harper Perennial. ISBN 978-0-06-123350-0. LCCN 99016754. OCLC 813854733.
• National Academy of Sciences (1999). Science and Creationism: A View from the National Academy of Sciences (2nd ed.). Washington, D.C.: National Academy Press. ISBN 978-0-309-06406-4. LCCN 99006259. OCLC 43803228. Retrieved 2015-01-17.
• Schuh, Randall T. (2000). Biological Systematics: Principles and Applications. Ithaca, NY: Cornell University Press. ISBN 978-0-8014-3675-8. LCCN 99042377. OCLC 42027466.
• Spencer, Herbert (1865). First Principles of a New System of Philosophy. New York: D. Appleton & Company. LCCN 15024188. OCLC 3015414.
• Wells, H. G.; Huxley, Julian; Wells, G. P. (1931) [Originally published 1929–1930]. The Science of Life. Garden City, NY: Doubleday, Doran & Company, Inc. LCCN 31003561. OCLC 968712.
• Wiley, Edward O.; Lieberman, Bruce S. (2011). Phylogenetics: Theory and Practice of Phylogenetic Systematics (2nd ed.). Hoboken, NJ: Wiley-Blackwell. doi:10.1002/9781118017883. ISBN 978-0-470-90596-8. LCCN 2010044283. OCLC 741259265.
• Wilson, Edward O. (1998). Consilience: The Unity of Knowledge. New York: Knopf. ISBN 978-0-679-45077-1. LCCN 97002816. OCLC 36528112.
• Wright, Sewall (1984) [Originally published 1968]. Genetic and Biometric Foundations. Evolution and the Genetics of Populations. Vol. 1. Chicago, IL: University of Chicago Press. ISBN 978-0-226-91038-3. LCCN 67025533. OCLC 246124737.
• Zetterberg, J. Peter, ed. (1983). Evolution Versus Creationism: The Public Education Controversy. Phoenix, AZ: Oryx Press. ISBN 978-0-89774-061-6. LCCN 82018795. OCLC 9393689.

Further reading

• Branch, Glenn; Mead, Louise (July 2008). "'Theory' in Theory and Practice". Evolution: Education and Outreach. 1 (3): 287–289. doi:10.1007/s12052-008-0056-5. ISSN 1936-6426.
• Dobzhansky, Theodosius (March 1973). "Nothing in Biology Makes Sense Except in the Light of Evolution". The American Biology Teacher. 35 (3): 125–129. CiteSeerX 10.1.1.324.2891. doi:10.2307/4444260. ISSN 0002-7685. JSTOR 4444260. S2CID 207358177.
• Lewis, Ralph W. (Winter 1987–1988). "Theory and the Fact of Evolution" (PDF). Creation/Evolution Journal. 8 (22): 34–37. ISSN 0738-6001. Retrieved 2015-01-21.
• National Academy of Sciences; Institute of Medicine (2008). Science, Evolution, and Creationism. Washington, D.C.: National Academies Press. ISBN 978-0-309-10586-6. LCCN 2007015904. OCLC 123539346. Retrieved 2015-01-19.

External links

• "Evolving Ideas: Isn't Evolution Just a Theory?". Evolution Library (Web resource). Evolution. Boston, MA: WGBH Educational Foundation; Clear Blue Sky Productions, Inc. 2001. OCLC 48165595. Retrieved 2015-01-21. Video requires QuickTime or RealPlayer plugin for viewing.
• Isaak, Mark, ed. (September 7, 2006). "Index to Creationist Claims: Claim CB910: No new species have been observed". TalkOrigins Archive. Houston, TX: The TalkOrigins Foundation, Inc. Retrieved 2015-01-21. Response to the claim that no examples of speciation have been observed.
• "Is Evolution a Theory or a Fact?". Evolution Resources from the National Academies. Washington, D.C.: National Academy of Sciences. Retrieved 2015-01-21.
• Howard, Jules (2016-02-05). "Do whales have nipples? Why discussing evolution in schools can occasionally be tricky". the Guardian. Retrieved 2016-02-05.
• "How Do We Know What Is True?" (animated video; 2:52))