Devolution (biological fallacy)

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In common parlance, "devolution", "de-evolution", or backward evolution is the notion that a species can generally evolve into more "primitive" forms by losing adaptations no longer necessary in a new environment. According to this view, changes from one biome to another may usher in pressures to weed out an obsolete function which is no longer useful for survival after the transition, and that the probability of losing a organic function in a new biome, via the conventional evolutionary pressures to "evolve", is more frequent and explainable than the synthesis of a new organic function. The scientific evidence for modern evolutionary synthesis has disproved the idea of "devolution".[1]

The popularized connotation of the word "evolution" leads many to misunderstand Darwin's theory of evolution in thinking that "evolution" requires some sort of "increasing complexity".[2] Yet the Darwinian theory of evolution does not reject the possibility of decreasing complexity (c.f. vestigiality) as the basis for some evolutionary change. Early scientific theories of the history of life on earth tried to account for species diversity as a result of acquisitions of various adaptations to the environment, and these included Lamarckism and orthogenesis. However, modern genetically-based biological evolution theory asserts that evolution occurs by non-teleological mechanisms such as natural selection, genetic drift, and mutation; hence "devolution", Larmarckism, and orthogenesis are rejected by modern evolutionary synthesis.

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[edit] Dollo's law

Main article: Dollo's law

Complex organs evolve in a lineage over many generations, and once lost they are unlikely to re-evolve. This observation is sometimes generalized to a hypothesis known as Dollo's law, which states that evolution is not reversible. This does not mean that similar engineering solutions cannot be found by natural selection. For instance the tail of the cetacea--whales, dolphins and porpoises which are evolved from formerly land-dwelling mammals--is an adaptation of the spinal column for propulsion in water. Unlike the tail of the mammal's marine ancestor, the Sarcopterygii, and the other teleosts, which move from side to side, the cetacean's tail moves up and down as it flexes its mammalian spine, but the function of the tail in providing propulsion is remarkably similar.

[edit] Use of the term by opponents of evolution

As with other modern sciences, biology is based on a methodological assumption of philosophical naturalism to study and explain the natural world, without assuming the existence or nonexistence of the supernatural. In contrast, creationism and intelligent design are based on teleology in seeking to prove the existence of an organizing principle behind natural laws and phenomena. Opponents of evolution use the teleological argument for the existence of God, and seek to displace evolution as the central organizing concept in biology. To do so, some redefine "evolution" in their terms, and introduce "devolution" to show that evolution theory is incorrect.

Examples include Mastropaulo,[3] who argues that "Change over time, 'definition one' of evolution, actually describes devolution to extinction, the exact opposite of evolution.... actual epidemiological data from human genetic disorders and fatal birth defects, identify 'natural selection,' the alleged 'primary mechanism' for evolution, as actually a mechanism for devolution to extinction, the exact opposite of evolution." and elsewhere,[4] "Evolution is the development of an organism from its chemicals or primitive state to its present state. Devolution is the sequence toward greater simplicity or disappearance or degeneration."

The term has been used in the play Inherit the Wind, the character of Matthew Brady (representative of William Jennings Bryan) using the term to argue that "ape devolved from man", mocking evolutionary theory by offering an alternative he considers just as plausible. In fact, the suggestion of ape degenerating from "man" was brought up by the early young-earth creationist George McReady Price in a work published before the Scopes Trial:

Accordingly, by every just rule of comparison and analogy, we may well declare that if there is any blood relationship between man and the anthropoid apes, it is the latter which have degenerated from the former, instead of the former having developed from the latter. I do not say that this is the true solution of this enigma; but I do say that there is far more scientific evidence in favour of this hypothesis than there ever has been in favour of the long popular theory than man is a developed animal.
—[5]

[edit] Streamlining evolution

"Devolution", the verb "devolve" and the past participle "devolved" are all common terms in science fiction for changes over time in populations of living things that make them less complex and remove some of their former adaptations. The terminology used herein is nontechnical, but the phenomenon is a real but counter-intuitive one, more accurately known as streamlining evolution. Since the development and maintenance of a feature such as an organ or a metabolite has an opportunity cost, changes in the environment that reduce the utility of an adaptation may mean that a higher evolutionary fitness is achieved by no longer using the adaptation, thus better using resources. This requires a mutation that inactivates one or more genes, perhaps by a change to DNA methylation or a methionine codon. Streamlining evolution allows evolution to remove features no longer of much/any use, like scaffolding on a completed bridge.

However, "devolution" in practice typically refers to changes that occur from a problem no longer existing rather than superior solutions existing. For instance, of the several hundred known species of animal that live their entire lives in total darkness, most have non-functional eyes rather than no eyes. This is due, for instance, to deterioration of the optic nerve. It occurs because mutations that prevent eye formation have low probability. However, several eyeless animal species, such as the Kauai cave wolf spider, who live in total darkness, and whose ancestry mostly had eyes, do exist. Together with gene duplication, streamlining evolution makes evolution surprisingly able to produce radical changes, despite being limited to successive, slight modifications.

[edit] See also

[edit] Notes and citations

  1. ^ TalkOrigins Archive response to Creationist claims - Claim CB932: Evolution of degenerate forms
  2. ^ Michael J. Dougherty. Is the human race evolving or devolving? Scientific American July 20, 1998.
  3. ^ http://www.csulb.edu/~jmastrop/data3.html Biology vs Evolution, Joseph Mastropaolo, Ph.D., Creation Research Society Quarterly 38: 151-158, 2001
  4. ^ Biology Eliminates Evolution and Confirms Genesis (pdf) (google cache [1])
  5. ^ George McReady Price, The Phantom of Organic Evolution, New York: New York: Fleming H. Revell, 1924, reprinted in Selected Works of George McCready Price, ed. Ronald L. Numbers, New York: Garland Publishing, 1995, ISBN 0-8153-1808-1. volume 7 of the series Creationism in Twentieth Century America. Chapter IX Section V, page 210-211 (pages 446-447 of reprint). Italics in original.
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