Hopeful Monster
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Hopeful Monster is the colloquial term used in evolutionary biology to describe an event of instantaneous-speciation, saltation, or systemic mutation, which contributes positively to the production of new major evolutionary groups. The memorable phrase was coined by the geneticist Richard Goldschmidt, who believed that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution.
In Goldschmidt's seminal work The Material Basis of Evolution, he wrote "the change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation."[1]
Goldschmidt's thesis however was universally rejected and widely ridiculed within the biological community, which favored the neo-Darwinian explanations of R.A. Fisher, J. B. S. Haldane and Sewall Wright.[2]
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[edit] Large scale mutations
In 1977 Stephen Jay Gould argued that the recent discovery of regulatory genes offered new evidence which supported some of Goldschmidt's postulates. Gould argued that instances of rapid evolution neither undermine Darwinian theory (as Goldschmidt believed) nor await immediate discreditation (as many neo-Darwinians thought).[1] Gould insisted that Darwin's belief in gradualism—which was largely inherited from the anti-catastrophic views of Charles Lyell—was never an essential component to Darwin's theory of evolution. Thomas Henry Huxley also warned Darwin that he had loaded his work "with an unnecessary difficulty in adopting Natura non facit saltum so unreservedly."[3] Huxley feared this assumption could discourage naturalists who believed that major leaps and cataclysms played a significant role in the history of life. Gould continued:
- "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 his infamous book of 1940, Goldschmidt specifically invokes rate genes as a potential maker of hopeful monsters: 'This basis is furnished by the existence of mutants producing monstrosities of the required type and the knowledge of embryonic determination, which permits a small rate change in early embryonic processes to produce a large effect embodying considerable parts of the organism.' 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."[1]
Nevertheless, Gould argued that Goldschmidt's "hopeful monster" concept was incorrect:
- "The developmental theme of the 'hopeful monster' (despite its inappropriate name, virtually guaranteed to inspire ridicule and opposition), based on the important concept of 'rate genes,' came first in Goldschmidt's thought, and always occupied more of his attention and research. Unfortunately, he bound this interesting challenge from development, a partially valid concept that could have been incorporated into a Darwinian framework as an auxiliary hypothesis (and now has been accepted, to a large extent, if under different names), to his truly oppositional and ultimately incorrect theory of systemic mutation, therefore winning anathema for his entire system. Goldschmidt may have acted as the architect of his own undoing, but much of his work should evoke sympathetic attention today."[4]
Most evolutionary biologists believe that small mutations are far more likely to be beneficial than macromutations.[5] Recent understanding of the genome has further undermined the Hopeful Monster model, because many dramatic mutations induced by X-rays in the laboratory are now known to involve deletion or rearrangement of entire genes, but DNA sequencing data from many species shows that in the wild these genes persist undisrupted for hundreds of millions of years. Macromutations do occur in the wild and in human genetic diseases, but are more often than not removed by natural selection. Nonetheless, some major rearrangements in the genome have been observed in species, and the idea of the adaptive landscape hints that very small changes may not always be able to pull a species out of an evolutionary rut.[citation needed]
[edit] Use by creationists
It has been common practice for creationists to confuse Goldschmidt's "hopeful monsters" with the theory of punctuated equilibrium, as proposed by Eldredge and Gould.[6] Punctuated equilibrium differs from hopeful monsters in that the former acts on populations rather than individuals, is far more gradual (taking 50,000 to 100,000 years), functions by isolating mechanisms (particularly allopatric speciation), and the latter says nothing of stasis. Creationists such as Luther Sutherland claim that both theories imply an absence of fossil evidence for evolution and thereby undermining the theory of Darwinian evolution. This claim is used by creationists to argue that "there are no transitional fossils." Paleontologists such as Niles Eldredge, Stephen Jay Gould, and Steven M. Stanley argued that transitional forms may be rare between species, but "they are abundant between larger groups."[7] Moreover, none of these paleontologists argued in support of Goldschmidt's "hopeful monster" hypothesis.
Steven M. Stanley argued that some of Goldschmidt's views err mainly in exaggerating the importance of "chromosomal rearrangements" leading to "rapid changes in growth gradients or developmental sequences, and on what we now call quantum speciation."[8]
[edit] Notes
- ^ a b c Goldschmidt, R. (1940) The Material Basis of Evolution. New Haven, CT: Yale University Press, pp. 205-206.
- ^ Gould, S. J. (1982). "The uses of heresey; an introduction to Richard Goldschmidt's The Material Basis of Evolution." pp. xiii-xlii. New Haven: Yale University Press.
- ^ Huxley, T. H. (1859). Letter to Charles Darwin. Nov. 23, 1859.
- ^ Gould, S. J. (2002). The Structure of Evolutionary Theory. Cambridge, MA: Harvard Univ. Press, p. 68.
- ^ Dawkins, Richard (1996). The Blind Watchmaker. New York: W. W. Norton & Co., p. 230-232.
- ^ Eldredge, Niles and S. J. Gould (1972). "Punctuated equilibria: an alternative to phyletic gradualism" In T.J.M. Schopf, ed., Models in Paleobiology. San Francisco: Freeman Cooper. pp. 82-115.
- ^ Gould, S. J. (1981)."Evolution as Fact and Theory." Discover 2 (May): 34-37.
- ^ Stanley, S. M. (1981) The New Evolutionary Timetable. New York: Basic Books, p. 135.
