Difference between revisions of "Definition of evolution"
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This is the idea that there is some last universal common ancestor, from which all plants, animals, fungi, and other life on Earth are directly descended. | This is the idea that there is some last universal common ancestor, from which all plants, animals, fungi, and other life on Earth are directly descended. | ||
| − | Webster's dictionary put it as, "...the development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny"<ref>Quoted in [http://www.talkorigins.org/faqs/evolution-definition.html What is Evolution], by Laurence Moran.</ref> | + | Webster's dictionary put it as, "...the development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny"<ref Name="TO">Quoted in [http://www.talkorigins.org/faqs/evolution-definition.html What is Evolution], by Laurence Moran.</ref> |
| + | Although it has been criticised on a number of grounds<ref>Laurence Moran on Talk.Origins criticises the definition for excluding prokaryotes, protozoa, and fungi, and for specifying ''gradual'' changes, and other reasons.</ref>, this is the main concept behind the definition provided by the Oxford Concise Science Dictionary: "The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3000 million years".<ref name="TO" /> | ||
| − | ''' | + | '''Change in gene frequency''' |
| − | E.O. Wilson defines | + | E.O. Wilson defines evolution as "any change in gene frequency in a population." Helena Curtis and N. Sue Barnes define evolution as "any change in the frequency of alleles within a gene pool from one generation to the next"<ref Name="TO" /> |
== Use of different definitions == | == Use of different definitions == | ||
Revision as of 13:19, April 9, 2007
The definition of evolution is itself part of the controversy over evolution. Several different meanings have been and still are used. Creationists charge that evolutionists often equivocate between different meanings[1], while evolutionists acknowledge that not clearly defining the term leads to confusion.[2]
Definitions
Change in the history of the universe
This includes biological change, and non-biological change, such as galaxy formation. Evolutionist Theodosius Dobzhansky (1900-1975) said, "Evolution comprises all the stages of the development of the universe: the cosmic, biological, and human or cultural developments. Attempts to restrict the concept of evolution to biology are gratuitous."[3]
The origin and development of life
Kerkut defined evolution as "the theory that all the living forms in the world have arisen from a single source which itself came from an inorganic form"[4]
However, evolutionists today generally reject this definition, as it includes the origin of life (abiogenesis). Natural selection can only operate once life has started.
The development of life from a common ancestor.
This is the idea that there is some last universal common ancestor, from which all plants, animals, fungi, and other life on Earth are directly descended.
Webster's dictionary put it as, "...the development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny"[5]
Although it has been criticised on a number of grounds[6], this is the main concept behind the definition provided by the Oxford Concise Science Dictionary: "The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3000 million years".[5]
Change in gene frequency
E.O. Wilson defines evolution as "any change in gene frequency in a population." Helena Curtis and N. Sue Barnes define evolution as "any change in the frequency of alleles within a gene pool from one generation to the next"[5]
Use of different definitions
When evolution is defined simply as "the gradual appearance of new forms of life" over geological time, then 55% of Americans agree with biologists and geologists that evolution has really occurred. Disagreement on this point comes mainly from Young Earth Creationists.
But when defined more narrowly as new forms of life coming into being "without any intervention from God", only 13% to 16% of Americans agree.
Advocates for the teaching of evolution as a finding of mainstream science tend to use two different meanings of "evolution".
- We have fossil evidence for evolution. It's a fact. (teacher in CNN article)
This apparently refers to the assertion that the appearance of new forms of life is supported by fossils (see carbon dating). But the context of the quote implies that the teacher was actually talking about the notion that "new species can evolve from older ones -- such as humans evolving from ancient apes." [1]
About half of the people who reject the materialist Theory of Evolution accept the fossil evidence of "gradual appearance" while rejecting mainstream biology's explanation that natural selection and unguided forces like mutation and copying errors is the cause.
Notes
- ↑ See, for example, Definitions as slippery as eels in Who’s really pushing ‘bad science’?, by Jonathan Sarfati.
- ↑ What is Evolution? by Laurence Moran.
- ↑ Quoted by Stephen E. Jones at http://members.iinet.net.au/~sejones/evolut01.html
- ↑ Implications of Evolution, p. 157, by Kerkut, G.A., quoted in Origin of life and the homochirality problem: is magnetochiral dichroism the solution? by Jonathan Sarfati.
- ↑ 5.0 5.1 5.2 Quoted in What is Evolution, by Laurence Moran.
- ↑ Laurence Moran on Talk.Origins criticises the definition for excluding prokaryotes, protozoa, and fungi, and for specifying gradual changes, and other reasons.