Hopeful Monster


Hopeful Monster

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 German born geneticist Richard Goldschmidt (1878-1958), who believed that small gradual changes could not bridge a hypothetical divide between microevolution and macroevolution.

In Richard Goldschmidt's seminal contribution to evolutionary biology, "The Material Basis of Evolution", he writes: "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." (1940, pp. 205-206)

His 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.

Hopeful Monsters Today

In 1977 Stephen Jay Gould argued [http://www.evolutionary.tripod.com/gould_nh_86_22-30.html ] that instances of rapid evolutionary change in brief geological timespans neither undermine Darwinian theory (as Goldschmidt believed) nor await discreditation (as many rigid neo-Darwinians at the time thought). The gradualism that Darwin inherited from anti-catastrophic geologists—especially Sir Charles Lyell—was never, Gould insisted, essential to his theory of evolution. In Darwin's own time his most passionate defender T. H. Huxley warned that this unnecessary element of "natura non facit saltum" would only dishearten those who believed that major leaps and cataclysms played significant roles in the natural history of life on Earth. Gould also wished that with the recent discovery of regulatory genes Goldschmidt's reputation and perhaps some of his contributions might now be seen in a favorable light.

:"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." (Gould, 1977, 24, 30)

Genetic mechanisms that may explain the emergence of "hopeful monsters" include evolutionary capacitance and homeotic mutations.

However, while Gould described some of the details of Goldschmidt's ideas as having been legitimate, he also pointed out that Goldschmidt's basic "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" (The Structure of Evolutionary Theory. Cambridge, MA: Harvard Univ. Press, 2002, p. 68).

Nevertheless, most evolutionary biologists believe that small mutations are much more likely to be beneficial than macromutations. By analogy, an archer facing at a target who changes his aim very slightly has a 50% chance of shooting closer to the mark, while a sudden spasm will surely send the arrow far away from it. More 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 they must generally be removed rapidly by natural selection. Nonetheless, some major rearrangements in the genome are observed within and between species, and the concept of adaptive landscape hints that very small changes may not always be able to pull a species out of an evolutionary rut.

Use by creationists

For decades some creationists have claimed a strong connection between Goldschmidt's "hopeful monster" idea and punctuated equilibrium, as proposed by Eldredge and Gould. Creationists such as Luther Sutherland claim that both Eldredge and Gould's theory of punctuated equilibrium and Goldschmidt's notion of "hopeful monsters" imply an absence of fossil evidence for evolution and thereby undermine Darwin. This claim is used by creationists in support of the creationist argument that "there are no transitional fossils." However, while paleontologists such as Niles Eldredge and Stephen Jay Gould, and later Steven M. Stanley [http://www.jhu.edu/~eps/faculty/stanley/stanleypubs.html] [http://wiki.cotch.net/index.php/Steven_M._Stanley] , argued that a "lack" (not an absence) of transitional fossils at the species-to-species level pointed to the importance of rapid evolutionary change (where tens of thousands of years is considered "rapid" from a geological perspective), and also relative species stability of large populations, none of these paleontologists ever made the creationist claim that there are no transitional fossils. Moreover, none of these paleontologists ever argued in support of Goldschmidt's "hopeful monster" idea, but the prominent evolutionary mechanisms resulting in punctuated equilibrium were considered to be those proposed by Ernst Mayr with his concepts of "parapatric speciation" and "allopatric speciation."

While rejecting Goldschmidt's basic "hopeful monster" idea as having any importance for evolution, Steven M. Stanley, like Gould, suggests that some of Goldschmidt's views, while apparently extreme, deviate little more from the neo-Darwinian synthesis than the current punctuational model and seem to 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."

References

*Goldschmidt, R. (1940) "The Material Basis of Evolution" New Haven, Conn., Yale University Press.
*Gould, S. J. (1977) [http://www.stephenjaygould.org/library/gould_hopeful-monsters.html "The Return of Hopeful Monsters"] "Natural History" 86 (June/July): 22-30.
*Stanley, S. M. (1981) "The New Evolutionary Timetable." New York: Basic Books. p. 135.

Notes

External links

* [http://www.stephenjaygould.org/people/richard_goldschmidt.html Richard Goldschmidt: A Biographical Sketch]
* [http://www.edwardgoldsmith.com/page29.html Richard Benedict Goldschmidt] : by Edward Goldsmith


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