Here is my essay that I wrote. Its a bit long but hopefully it will add to the thread
Comparing Natural Selection and Punctuated Equilibrium
The theory of evolution is one of the best-known scientific theories around. “The subject is fascinating because it attempts to answer one of the most basic human questions: Where did life, and human beings, come from? The theory of evolution proposes that life and humans arose through a natural process” (Howstuffworks). In 1959, Charles Darwin’s Origin of Species revolutionized evolutionary thought (Bowler 141). Within Origin of Species, Darwin provides the mechanism through which evolutionary change can occur-Natural Selection. Natural Selection is, “Individuals with qualities that made them better adjusted to their environments or gave them higher fitness. Because more individuals are born than survive to breed, constant winnowing of the less fit- a natural selection- should occur, leading to a population that is well adapted to the environment it inhabits. When environmental conditions change, populations require new properties to maintain their fitness. Either the survival of a sufficient number of individuals with suitable traits leads to an eventual adaptation of the population as a whole, or the population becomes extinct” (Funk & Wagnells 20). However, this essay does not only plan to discuss only Darwin’s theory of Natural Selection, it plans to compare it to another famous mechanism for evolutionary change, Stephan J Gould’s Punctuated Equilibrium. In 1972, Gould and his colleague, Niles Eldredge, proposed this idea of Punctuated change. According to this theory, “Species do in fact tend to remain stable for long periods of time and then to change relatively abruptly-or rather, to be replaced by newer and more successful forms. These sudden changes are the ‘punctuations’ in the state of equilibrium that give this concept its name” (Funk & Wagnells 24). Both theories were very influential, however they differ in the way they produce evolutionary change in how they explain the fossil record, and in the problems associated with the theories.
The theories of Natural Selection and Punctuated Equilibrium differ greatly in terms of the mode in which evolutionary change is produced. Darwin’s Natural Selection requires four fundamental aspects, V.O.S.S. (Nichols Oct 1, 2003). The first of these is Variation which, according to Darwin, is a precondition for evolutionary change. This is an empirical observation that illustrates biological individuality; all animal populations have differences of heredity and variation in the species. Without this variation, evolutionary change would not occur according to the theory of Natural Selection. The second letter of the V.O.S.S. formula is Offspring of Offspring. This states that in every generation, more offspring are born then will ever survive. This point will be drawn upon later on in the essay in terms of external influences on the theory. The third letter in the formula is Struggle for Existence. This is the result of V+O, or in other words, competition within the species. If most potential life does not survive, it creates enormous pressure to compete for the available resources. Variation within the species plays a role in sorting out the survivors who will go on to breed from those who do not survive, resulting in the genetic difference being lost. The final part of the formula is Selection. Slow gradual change takes place in an animal population if the environment is stable. Genetic traits that allow animals to survive are conservative during this time. If the environment changes in significant ways, those individuals who deviate from the norm offer a solution for survival. (Nichols Oct 1, 2003) It is also worth mentioning that, “What natural selection cannot do, is to modify the structure of one species, without giving it any advantage” (Darwin 51). Now that the mechanism for evolution under natural selection is clear, Gould’s mechanism for evolutionary change under Punctuated Equilibrium will be discussed.
According to the theory of Punctuated Equilibrium, species tend to stay the same until some “punctuation” occurs (Funk & Wagnells 24). Gould suggests that there are three different things that can cause this “punctuation,” they are: regulatory gene change, neoteny, and the Cometary Impact theory. Gould draws upon Richard Goldschmidt’s “Synthetic Theory of Evolution.” In Gould’s essay, “Return of the Hopeful Monster,” from his book “The Panda’s Thumb,” he states that, “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’” (Gould 192). Gould goes on further to state that, “If we do not invoke discontinuous change by small alteration in rates of development, I do not see how most major evolutionary transitions can be accomplished at all” (Gould 192). This regulatory gene change leads into the second manner in which punctuated change can occur, neoteny. In Gould’s essay, “The Child as Man’s Real Father” from his book “Ever Since Darwin” Gould states his belief that neoteny can lead to evolutionary change; “But since neoteny and ******** development are generally linked, retardation does provide a mechanism for the easy retention of any juvenile feature that suits the adult life style of descendants. In fact, juvenile features are a storehouse of potential adaptations for descendants, and they can be utilized easily if development is strongly ******** in time (Gould 68). This point was made more clearly in Professor Nichols November 5, 2003 lecture. According to this lecture, new species evolve because they retain and re-shuffle the juvenile characteristics of their ancestors. The regulatory genes represent a pattern of growth, which leads to an adult appearance in the species; the regulatory genes turn on and off at particular times. This process is most active during the maturation process. A final, and most drastic explanation for punctuated evolutionary change put forth by Gould is the Cometary Impact theory. In Gould’s essay, “ The Cosmic Dance of Siva” from the book, “The Flamingo’s Smile,” he states his belief in mass extinction as a cause of evolutionary change. The idea is that materials have collided with Earth and led to mass extinctions. Gould does have some compelling evidence for this view. First of all, “High levels of iridium in rocks at the Cretaceous Tertiary boundary provided the first solid evidence for coincidence between extraterrestrial impact and time of extinction…Iridium in surface rocks arrives largely from extraterrestrial sources-asteroids, meteorites, and comets” (Gould 440-441). Another impressive fact stated in the essay mentioned is that, “David Raup and Jack Sepkoski, working from extensive compilations of the life and death times for fossil families, found a 26-million-year periodicity in extinctions during the past 225 million years” (Gould 441) This coincides with what, “Walter Alvarez and Richard A. Muller find of periodicity, similar in timing and spacing of 28.4 million year to the Raup-Sepkoski extinction peaks, for well-dated impact craters on Earth with diameters in excess of ten kilometers” (Gould 441). To conclude this point Gould states, “If mass extinctions are so frequent, so profound in their effects, and caused fundamentally by an extraterrestrial agency so catastrophic in impact and so utterly beyond the power of organisms to anticipate, then life’s history either has an irreducible randomness or operates by new and undiscovered rules for perturbations, not by laws that regulate predictable competition during normal times” (Gould 446). The ideas proposed by Gould clearly operate in a world of stasis and are abruptly punctuated causing macro evolutionary change. It is easy to see the major difference between Natural Selection and Punctuated Equilibrium; Natural Selection is a gradual and continuous process while Punctuated Equilibrium is discontinuous.
Since the two theories are opposite to one another, can the fossil record provide any information as to which one is more accurate? First, let’s start with Natural Selection. Charles Darwin recognized the problem with this own theory in terms of the fossil record. He states, “Why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms?” (Darwin 75). The only answer Darwin can give is this, “I will here only state that I believe the answer mainly lies in the record being incomparably less perfect than is generally supposed; the imperfection of the record being chiefly due to organic beings not inhabiting profound depths of the sea, and to their remains being embedded and preserved to a future age only in masses of sediment sufficiently thick and extensive to withstand an enormous amount of future degradation; and such fossiliferous masses can be accumulated only where much sediment is deposited on the shallow bed of the sea, whilst it slowly subsides. These contingencies will concur only rarely, and after enormously long intervals. Whilst the bed of the sea is stationary or is rising, or when very little sediment is being deposited, there will be blanks in our geological history” (Darwin 76). The evidence for Punctuated Equilibrium in the fossil record is diametrically opposed of Natural Selection. Gould states his view on this topic in his essay “Episodic Evolutionary Change” from his book, “The Panda’s Thumb, “The history of most fossil species includes two features particularly inconsistent with gradualism: 1. Stasis. Most species exhibit no directional change during their tenure on earth. They appear in the fossil record looking much the same, as when they disappear, morphological change is usually limited and directionless. 2. Sudden appearance. In any local area, a species does not arise gradually by the steady transformation of its ancestors; it appears all at once and ‘fully formed’” (Gould 182). It is difficult to state that one theory has an edge over the other; it all depends on how the fossil evidence is interpreted.
With any theory, there comes criticism and problems. There are many problems and criticisms for Natural Selection. Once again Darwin acknowledges his theory’s flaw, “ Can we believe that natural selection could produce, on the one hand…on the other hand, organs of such wonderful structure, as the eye, of which we hardly as yet fully understand the inimitable perfection?” (Darwin 75). Darwin tries his best to explain how the eye came about but even he has his doubts, this is revealed when he says, “To suppose that the eye, with all it inimitable contrivances for adjusting the focus to different distances…could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree” (Darwin 85). A criticism that follows Natural Selection is that it, “Bears an uncanny resemblance to the political economic theory of early capitalism as developed by the Scottish economics” (Lewontin 10). During the November 26, 2003 lecture, Professor Nichols mentioned Gould’s criticism, which wed his science with his political beliefs. Gould feared that a nuclear war would lead to mass extinction resembling that of the Cometary Impact theory. This could have been a reason why Gould took to the Cometary Impact theory; he went against his own word that one cannot draw any moral/political lessons from nature.
In light of what has been discussed, it is evident that both theories have left a major imprint on the science of Evolution. Gould is often said to be the greatest evolutionary thinker since Darwin. Both men have contributed a great deal, and their ideas will linger with us for a long time if not forever. Darwin’s theory of Natural Selection is still talked about today. In fact Gould insists that Natural Selection is still involved in the process of evolution, just not to the point where it is causing major evolutionary change (Gould 188).
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