Punctuated Equilibrium

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The theory of punctuated equilibrium according to the American Museum of Natural History "asserts that evolution occurs in dramatic spurts interspersed with long periods of stasis".[1] The punctuated equilibrium theory was developed by the paleontologists Stephen Gould and Niles Eldridge due to the fossil record not being able to support an evolutionary paradigm which adhered to strict phyletic gradualism, in their paper Punctuated Equilibria: An Alternative to Phyletic Gradualism.[2]

"Still, if evolution is gradual, there should be a fossilized record of small, incremental changes on the way to a new species. But in many cases, scientists have been unable to find most of these intermediate forms. Darwin himself was shaken by their absence. His conclusion was that the fossil record lacked these transitional stages, because it was so incomplete. That is certainly true in many cases, because the chances of each of those critical changing forms having been preserved as fossils are small. But in 1972, evolutionary scientists Stephen Jay Gould and Niles Eldredge proposed another explanation which they called 'punctuated equilibrium.'[3] That is, species are generally stable, changing little for millions of years. This leisurely pace is 'punctuated' by a rapid burst of change that results in a new species and that leaves few fossils behind."

-Prentice-Hall on PBS[4]

The theory caused much controversy and received much criticism, forming part of the "Darwin Wars" between such scientists as Steven Jay Gould and Richard Lewontin on one side and "Ultra-Darwinists" such as Richard Dawkins on the other. However, there was no controversy as to whether gradual change through natural selection was the most important evolutionary process. Gould argued for a greater rate of evolution, but not greater changes per mutation.Citation?

Contents

Proposed Methodology

The theory of punctuated equilibrium is briefly outlined below:[5]

  • 1. A species exists in the environment with many generations going by with little change (and members of this species occasionally being fossilized)
  • 2. Through interbreeding the change in the species is kept low
  • 3. There is a population at the edge of the general area that the species inhabits.
  • 4. This population becomes isolated
  • 5. Because this is a new environment, there are new pressures on the population
  • 6. As this is a smaller population, genetic drift is also increased
  • 7. 5+6 mean a greater rate of evolution, and in a different direction
  • 8. Over a long period of time, the population might no longer be able to interbreed (new species)
  • 9. If circumstances change again (i.e. the new species is reintroduced to the parent species), this new species may drive the other species to extinction.
  • 10. This new population would grow, and become static once more

As the new population developed quickly (as little as 100,000 years[6]) and was in an isolated area, they would leave few fossils.[7] This, according to Dr. Niles Eldredge, who proposed the theory along with Stephen Jay Gould[8], is consistent with the fossil record.[9]

Historical Development

The development of a new evolutionary school of thought occurring due to the fossil record not supporting the evolutionary position was not unprecedented. In 1930, Austin H. Clark, an American evolutionary zoologist who wrote 630 articles and books in six languages, came up with an evolutionary hypothesis called zoogenesis which postulated that each of the major types of life forms evolved separately and independently from all the others.[10] Prior to publishing his work entitled The New Evolution: Zoogenesis, Clark wrote in a journal article published in the Quarterly Review of Biology that "so far as concerns the major groups of animals, the creationists seem to have the better of the argument. There is not the slightest evidence that any one of the major groups arose from any other."[11]

The evolutionary thinking of Richard Goldschmidt influenced Gould. In a 1977 in a paper entitled, ‘The Return of the Hopeful Monsters Gould wrote that when he studied evolutionary biology in graduate school that "official rebuke and derision focused upon Richard Goldschmidt". Nevertheless, Gould also wrote:

I do, however, predict that during this decade Goldschmidt will be largely vindicated in the world of evolutionary biology.....As a Darwinian, I wish to defend Goldschmidt's postulate that macroevolution is not simply microevolution extrapolated, and that major structural transitions can occur rapidly without a smooth series of intermediate stages....In my own, strongly biased opinion, the problem of reconciling evident discontinuity in macroevolution with Darwinism is largely solved by the observation that small changes early in embryology accumulate through growth to yield profound differences among adults.[12]
The Harvard biologist Ernst Mayr comments on Gould's essay, 'The Return of the Hopeful Monsters' by stating the following:
Gould does not clearly distinguish between the magnitude of the structural change and the "locale" where it may occur. As a result, his discussion was seen by many as an endorsement of Goldschmidt's hopeful monster theory....

It is now clear that the basic difference between the moderate and drastic version of the theory of punctuated equilibria is that in the moderate version a gradual, albeit rapid and sometimes drastic genetic restructuring of populations takes place, while in the Goldschmidtian version a systemic mutation produces a single individual, a hopeful monster, which starts a new evolutionary tradition.

Even though some of the statements of Eldredge, Gould, and Stanley, made in the 1970s, sounded as if they had favored the Goldschmidtian version, they clearly distanced themselves from it in their more recent discussions. When postulating saltations, says Gould (1980), "I do not refer to the saltational of entire designs complete in all their complex and integrated features...instead, I envisage a potential saltational origin for the essential features of key adaptions. "[13]

Similarly, creation scientist Dr. Don Batten concurs with the Harvard evolutionist Ernst Mayr and states that in 1982 Gould distanced himself from "Hopeful Monsters" and cites Gould stating that "Punctuated equilibrium is not a theory of macromutation, it is not a theory of any genetic process" although Dr. Batten also cites Gould admitting to having supported "certain forms of macromutational theory … though not in the context of punctuated equilibrium."[14] Dr. Batten further states regarding the theory of Punctuated Equilibrium (PE) the following: "By the time of their 21st anniversary review of PE, Gould and Eldridge had retracted to proposing PE as ‘a complement to phyletic gradualism’. This is a rather major backdown on the brashness of their claims in 1972, and especially Gould’s claims up to 1980..."[15]

In 1986, Niles Eldredge published his work Time Frames: the Re- thinking of Darwinian Evolution and the Theory of Punctuated Equilibria in which he wrote: ‘This book is my version of the story of “punctuated equilibria” … {emphasis added). This of course suggested that Eldridge wished to remove himself from other versions.[16] According to Dr. Batten, this was because Niles Eldredge had been "less dogmatic than Gould had been in the 1970s about the lack of gradual change in the fossil record". In 1986, Niles Eldridge took objection to the "hopeful monster" association with the theory of Punctuated Equilibrium and wrote: "The assertion that punctuated equilibria represents a resurrection of Goldschmidt’s "macromutations" and "hopeful monsters" remains the most serious and irksome misconstrual of our ideas." Eldridge also added that "The most common misconception about "punctuated equilibria" - that Gould and I proposed a saltationist model of overnight change supposedly based on sudden mutations with large-scale effects (macromutations á la Richard Goldschmidt)..."[17]

Gradualism

The morphological discontinuity and the geologic time scales involved (i.e decades or hundreds of years instead of thousands or millions) puts Punctuated Equilibrium in direct contrast with Gradualism; essentially an acknowledgement that species appeared suddenly in advanced stages without the gradual transitions required for a common ancestor. The lack of transitional forms in the fossil record troubled Darwin himself, who tried to explain it through the then-incomplete knowledge of the fossil record.[4]

Falsifiability

The Biotic Message: Evolution Versus Message Theory by Walter ReMine accuses Punctuated Equilibrium of being unfalsifiable, of simply creating an unsubstantiated hypothesis to explain away the growing body of evidence seen from the fossil record that evolution is not constant and gradual, and that transitional forms don't exist.

"So is punctuated equilibrium testable? Gould says that a series of fossils showing gradual development of an adaptation would refute punctuated equilibrium. ReMine points out the 'no lose' situation that Gould and company have created here: if the fossils show systematic gaps, then the punctuated equilibrium model of evolution is 'proven', but if the fossils show gradualism, then the standard neo-Darwinian model of evolution is proven. In other words, evolution itself is no longer falsifiable! Punctuated equilibrium and neoDarwinism are both now part of the evolutionists' grab-bag of conflicting theories as Gould and Eldredge now view punctuated equilibrium as an addition to evolutionary theory rather than an alternative."

-Don Batten, review of "The Biotic Message" in Creation[18]

Marxist thought and punctuated equilibrium

Marxist and Hegelian thought had an influence on Gould. He said that he learned communism "on his father's knee", that his father was a Marxist, and that his politics were very different from his father’s. This suggests that he was sympathetic to Marxism but not actually a Marxist.[19][20] Gould wrote:

Hegel's dialectical laws, translated into a materialist context, have become the official 'state philosophy' of many socialist nations. These laws of change are explicitly punctuational, as befits a theory of revolutionary transformation in human society. In the light of this official philosophy, it is not at all surprising that a punctuational view of speciation [the evolutionary process by which new species are formed] much like our own . . . has long been favored by many Russian paleontologists. It may also not be irrelevant to our personal preferences that one of us [Gould] learned his Marxism, literally at his daddy's knee.[21]

Some advocates of the evolutionary position have taken exception to the influence of Marxist thinking on Gould's evolutionary thought.[22] Harvard professor, E. O. Wilson, wrote concerning Gould that "He's willing to denigrate his own field of evolutionary biology in order to downgrade the enemy, sociobiology, which is a small but important branch of evolutionary biology. When Darwin conflicts with Marx, Darwin goes."[23] The evolutionist Michael Ruse wrote, "Quite openly, one of the leading punctuated equilibrists, Stephen Jay Gould, admits to his Marxism, and lauds the way in which his science is informed by his beliefs."[24]

See also

External Links

Notes

  1. http://www.amnh.org/science/divisions/paleo/bio.php?scientist=eldredge
  2. "Competing Hypotheses About the Pace of Evolution." Understanding Evolution. University of California Museum of Paleontology. 29 April 2012.
  3. Punctuated Equilibria: An Alternative to Phyletic Gradualism. Eldredge, N. and Stephen J. Gould. 1972.
  4. 4.0 4.1 Prentice-Hall Inc. "Punctuated Equilibrium."
  5. http://evolution.berkeley.edu/evosite/evo101/VIIA1bPunctuated.shtml
    http://www.pbs.org/wgbh/evolution/library/03/5/l_035_01.html
  6. http://evolution.berkeley.edu/evosite/evo101/VIIA1aHypotheses.shtml
  7. http://www.pbs.org/wgbh/evolution/library/03/5/l_035_01.html
  8. http://www.pbs.org/wgbh/evolution/library/03/5/l_035_01.html
  9. http://www.amnh.org/learn/courses/evolution_resource1.php
  10. http://creation.com/zoogenesis-a-theory-of-desperation
  11. http://creation.com/zoogenesis-a-theory-of-desperation#endRef4
  12. http://www.stephenjaygould.org/library/gould_hopeful-monsters.html
  13. Ernst Mayr, 1982a. Speciation and macroevolution. Evolution 36, page 1128
  14. http://creation.com/punctuated-equilibrium-come-of-age
  15. http://creation.com/punctuated-equilibrium-come-of-age
  16. http://creation.com/punctuated-equilibrium-come-of-age
  17. http://creation.com/punctuated-equilibrium-come-of-age
  18. Batten, Don (1997). "The Biotic Message: Evolution versus Message Theory." CenTech J. Vol. 3, No. 11, pp. 295-296.
  19. http://www.worldviewtimes.com/article.php/articleid-1739
  20. http://creation.com/what-is-the-evidence-that-gould-was-a-marxist
  21. http://www.worldviewtimes.com/article.php/articleid-1739
  22. http://www.worldviewtimes.com/article.php/articleid-1739
  23. http://www.worldviewtimes.com/article.php/articleid-1739
  24. http://www.worldviewtimes.com/article.php/articleid-1739
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