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The Origin of Species by Punctuated Equilibria
If you have been reading the recent creationist literature, you might come to the conclusion that the biologists have completely overturned Darwin. Thus, we have Duane Gish saying:
Or this news item in the September 22, 1981, issue of Awake!: New Debate Among Evolutionists
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Even science reporters seem to lend credence to these views. A November 1981 "Nova" television program, entitled "Did Darwin Get It Wrong?" concludes that, yes, Darwin was wrong and modern biologists and paleontologists believe that evolution occurs in instantaneous steps. Francis Hitching does the same thing at greater length in an article, "Was Darwin Wrong?" in the April 1982 issue of Life magazine and in a book, The Neck of the Giraffe: Where Darwin Went Wrong. The Eldredge and Gould (1977) hypothesis of punctuated equilibria figures prominently in such reports. The very name itself, an unfortunate choice of words, implies instant changes or jumps followed by constancy. Does punctuated equilibria deny Darwin?
First of all, what does the punctuated equilibria hypothesis really state? Certainly the account by Eldredge and Gould must be considered authoritative:
The fossil record at the species level of detail in a local stratigraphic section will show a species in morphological stasis during most of its existence, perhaps showing minor directional changes, and perhaps followed by ". . . a break with essentially sudden replacement of ancestors with descendents; this break may record the extinction or emigration of a parental species and the immigration of a successful descendent rapidly evolved elsewhere in a small, peripherally isolated population (Gould and Eldredge, 1977). Gould essentially says the same in his article, "Evolution's Erratic Pace" (1977).
How long does speciation take? In other words, how "instantaneous" are the "punctuations"? Gould says hundreds, even thousands of years (1977; 1979). Lewin quotes Gould as saying, "I'd be happy to see speciation taking place over, say, 50,000 years . . . " (1980). Fifty thousand years may be an "instant" in the geological record, but in human terms it is a very long time. In creationist terms, it is five times the age of the universe!
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What are the implications for macroevolution? According to Gould and Eldredge:
Thus, for example, mammals evolved gradually from reptiles during the length of the Permian and Triassic periods as the small morphological changes from hundreds of successive speciations accumulated. There is abundant fossil evidence for this kind of slow, gradual change. It is a far cry from the reptile-egg-hatching-a-bird idea of Schindewolf (not Goldschmidt) that the creationists use to describe the punctuated equilibria hypothesis.
This doesn't sound like a radical revision of evolutionary theory. As Gould and Eldredge  further state:
And it certainly does not discard or contradict Darwinism! Gould also says:
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The above considerations show that the creationists' depiction of punctuated equilibria is totally inaccurate. Gould complains, "It's so utterly infuriating to find oneself quoted, consciously incorrectly, by creationists. . . . None of this controversy within evolutionary theory should give any comfort, not the slightest iota, to any creationist" (Godfrey, 1981). But perhaps he and Eldredge are partly responsible for these misunderstandings because of the way in which they presented their hypothesis. They contrasted it with phyletic gradualisma model of "a slow steady shift in the mean phenotypic expression" of entire populations over millions of years" (Eldredge, 1974). They assert that this model was the accepted view among most paleontologists and proponents of the modern synthetic theory of evolution. They also claim that this view is implied in Darwin's writings, although they quickly point out that it is not a necessary consequence of Darwinian theory.
Perhaps many of their paleontological predecessors and colleagues did subscribe to that model, but I don't think it would be correct to say it characterized the views of the leading proponents of the synthetic theory. Templeton and Giddings, in a letter to Science (February 20, 1981, p. 770), assembled the following three exerpts:
In addition, Simpson wrote: "Some groups have been changed rapidly while others were remaining practically unchanged. The same group is commonly seen to have changed rapidly at some time in its history and slowly or not at all in others" (1950).
In another work, Simpson presents the terms horotely, bradytely, tachytely, and quantum evolution to describe and categorize the wide variation in evolutionary rates (1953). In this same work, he presents a diagram illustrating the patterns of evolutionary change of some characters of the horse lineage (p. 265). Some of the cheek tooth characters show a "phyletic gradualism" pattern, but the foot mechanism shows a decidely "punctuated equilibria" pattern, while size shows a mixture of the two types. Finally, the punctuated equilibria hypothesis itself was first proposed (sans name) by Ernst Mayr (1954; 1963; 1970). Mayr considered it a part of modern neo-Darwinism (Mayr, 1967). Eldredge and Gould contributed the provocative name and thrust it upon the paleontological world. (For Mayr's comments on this, see Goldberg, 1985).
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All the scientists cited above are considered strong proponents of the "classic" synthetic theory of evolution, yet none of them was "hung up" on "phyletic gradualism." But what about the author of the following?
The above excerpts describe almost all the elements of the punctuated equilibria hypothesis and even speculate about species selection, a related hypothesis. The only element missing is the explicit identification of the short periods of modification with the periods of speciation or phyletic branching! These excerpts, taken from Charles Darwin's Origin of Species (Modern Library Edition, pp. 89 and 357, respectively), are amazingly parallel to the passages from Gould and Eldredge quoted previously.
Punctuated equilibria is not new or revolutionary; it simply shifts the emphasis among a number of classic evolutionary mechanisms. And it strengthens Darwinism insofar as it better reconciles the synthetic theory with the fossil record. Because variation within species is geographically rather than temporally distributed, one will not be likely to see it in stratigraphic sections which represent only one or a few points in the spatial range of a species (Gould and Eldredge, 1977). The work of Williamson (1981; and summarized in Science, November 6, 1981, p. 645, and Newsweek, December 7, 1981, p. 114), who studied an instance of a fossil record continuous over several million years, appears to be a case of punctuated equilibria in which the short-lived transition forms in the speciation process have been preserved as fossils.
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Since this article was written, Eldredge has published a book-length account of the theory of punctuated equilibria entitled Time Frames (Simon and Schuster, 1985).
Eldredge, N. 1974. "Testing Evolutionary Hypotheses in Paleontology: A Comment on Makurath and Anderson (1973)." Evolution. 28:3:479-481.
Fisher, R. A. 1958. The Genetical Theory of Natural Selection. 2nd ed. Dover, p. 153.
Gish, D. 1981. "The Genesis War." Science Digest. 89:9:85.
Godfrey, L. R. 1981. "The Flood of Antievolutionism." Natural History. 90:6:4-10. See p. 97.
Goldberg, J. R. 1985. "The Eureka Moment: Ernst Mayr." Science Digest. 93:11:67, 94, 97. See p. 10.
Gould, S. J. 1977. "Evolution's Erratic Pace." Natural History 86:5:12-16.
Gould, S. J., and Eldredge, N. 1977. "Punctuated Equilibria: The Tempo and Mode of Evolution Reconsidered." Paleobiology. 3:115-151.
Haldane, J. B. S. 1924. Transcripts of the Cambridge Philosophical Society. 23:19-41.
Lewin, R. 1981. "Evolutionary Theory Under Fire." Science. 210:4472:883-887.
Mayr, E. 1954. "Change of Genetic Environment and Evolution." In J. Huxley, A. C. Hardy, and E. B. Ford (eds.), Evolution as a Process. London: Allen and Unwin, pp. 157-180.
Simpson, G. G. 1944. Tempo and Mode in Evolution. New York: Columbia University Press.
Williamson, P. G. 1981. "Paleontological Documentation of Speciation in Cenozoic Molluscs from Turkana Basin." Nature (London). 293:437-443.
Wright S. 1949. "Population Structure in Evolution." Proceedings of the American Philosophical Society. 93:471-478.
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