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Hopeful monster

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Hopeful monster also known as the hopeful monsters hypothesis is a biological theory which suggests that major evolutionary transformations have occurred in large leaps between species due to macromutations.

Contents

[edit] History

[edit] Richard Goldschmidt

The German geneticist Richard Goldschmidt (1878 – 1958) was the first scientist to use the term "hopeful monster". Goldschmidt thought that small gradual changes could not bridge the hypothetical divide between microevolution and macroevolution. In his book The Material Basis of Evolution (1940) 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." Goldschmidt believed the large changes in evolution were caused by macromutations (large mutations). His ideas about macromutations became known as the hopeful monster hypothesis which is considered a type of saltational evolution.[1]

According to Goldschmidt "biologists seem inclined to think that becuase they have not themselves seen a 'large' mutation, such a thing cannot be possible. But such a mutation need only be an event of the most extraordinary rarity to provide the world with the important material for evolution".[2] Goldschmidt believed that the neo-Darwinian view of gradual accumulation of small mutations was important but could only account for variation within species (microevolution) and wasn't a powerful enough source for the origin of evolutionary novelty to explain new species. Instead he believed that big genetic differences between species required profound "macro-mutations" a source for large genetic changes (macroevolution) which once in a while could occur as a "hopeful monster".[3][4]

Goldschmidt is usually referred to as a non-Darwinian, however he did not object to the general microevolutionary principles of the Darwinians. He only veered from the synthetic theory in his belief that a new species develops suddenly through discontinuous variation, or macromutation. Goldschmidt presented his hypothesis when neo-Darwinism was becoming dominant in the 1940's and 1950's and he strongly protested against the strict gradualism of neo-Darwinian theorists. Becuase of this his ideas were seen as highly unorthodox of the time by most scientists and were greatly subjected to ridicule and scorn.[5] However there has been a recent interest in the ideas of Goldschmidt in the field of evolutionary developmental biology as some scientists are convinced he was not entirely wrong.

[edit] Otto Schindewolf

Otto Schindewolf (1896 – 1971) a German paleontologist also supported macromutations as part of his evolutionary theory. He was know for presenting an alternative interpretation of the fossil record based on his ideas of orthogenesis, saltational evolution and extraterrestrial impacts opposed to gradualism. Schindewolf's theory was a form of orthogenesis, which stated that variation tends to move in a predetermined direction.[6] His theory became known as typostrophism and stated that evolution occurs due to a periodic cyclic model of evolutionary processes which are predestined to go through a life cycle dictated by factors internal to the organism.[7]

Part of his 'typostrophe' theory advocated sudden evolutionary change by macromutations but he later dropped this view (see below). His theory of orthogenesis (straight-line evolution) and eventual decay, claimed to be embedded within a cyclical view of the evolutionary process. According to (Levy, 2002) Schindewolf theory also proposed that mass extinctions, especially the ones at the end of the Permian period 225 million years ago, were the result of cosmic radiation caused by supernova explosions. Schindewolf speculated that a supernova star explosion could emit radiation which could be lethal to organisms if close enough to earth. He proposed that the radiation from a supernova could have two effects, one is extinguishing many species of life and the other that the radiation may cause macromutations which could cause new species to originate.[8] Schindewolf was the only scientist to have speculated that the first bird may have hatched from a reptile's egg.[9] It was only a speculation and he abandoned the view of macromutations in later publications.[10]

His book Basic Questions in Paleontology was published in German in 1950 and was translated into English in 1994 with a foreword written by Stephen Jay Gould.

[edit] Stephen Jay Gould

Stephen Jay Gould (1941 – 2002) had attempted to update the ideas of Goldschmidt by redefining the concept of "hopeful monster" in a way that can be kept in the neo-Darwinian framework via an extension.[11] In an article titled The Return of Hopeful Monsters (1977)[12] Gould argued that the recent discovery of regulatory genes offered new evidence which supported some of Goldschmidt's postulates and that small changes in the embryological "contraint systems" can produce large morphological transformation in the adult, and possibly macro-evolutionary pathways.[13] Gould's re-definition of the hopeful monster is different to that of Goldschmidt and they should not be confused with eachother.

[edit] Criticism

Many scientists rejected the hopeful monster hypothesis as genetical research seemed to show that large mutations would be lethal.[14] In response to this Goldschmidt suggested that, from time to time, big mutations can occur and although the majority of these would have been lethal, a very small number would have been compatible with survival. The most common criticism however; came from the early neo-Darwinian theorists who asked the question "how does a hopeful monster find a mate?". These scientists were skeptical of the idea of hopeful monsters as without more than one hopeful monster there would be no possibility of breeding or establishing a new population and thus would be no chance of a new species forming.[15]

In response to this criticism, Patrick Bateson wrote in Sudden Changes in Ontogeny and Phylogeny (1984):

Hopeful monsters were disparaged on the grounds that even if a big change in the phenotype could occur as a result of a mutation, the hopeful monster would be a novelty on its own with no possibility of finding a mate. With a mate there would no new species. However, if we suppose that, somehow or other, there were enough hopeful monsters to breed successfully with each other, the possibility exists of competition between the hopeful monsters and the stock from they sprang. It is not at all difficult to suppose that, by the process of natural selection, hopeful monsters could quickly replace their competitors if they were better adapted to the environment. No new fancy principles of evolution are involved here.[16]

[edit] Modern science

Some modern scientists have written that hopeful monsters are neither impossible nor should be seen as anti-Darwinian because even if proven to exist would not replace the evidence for gradual evolution by mutation but supplement it. The early neo-Darwinian synthesis theorists had rejected hopeful monsters due to lack of evidence; however there is now evidence that Goldschmidt was not entirely wrong.

Richard Dawkins wrote in his book Climbing Mount Improbable (1996):

My suggestion is that Scyllarus may actually present an example in the wild of a homeotic mutation, analogous to antennapedia in Drosophila in the laboratory. Unlike antennapedia, this mutation has been incorporated into an actual evolutionary change in nature. My tentative conjecture is that an ancestral Scyllarid mutated homeotically, slipping the developmental subroutine appropriate to a uropod into a segment where an antenna ought to be, and that the change conferred some benefit. If I am right, it would constitute a rare example of a macro-mutation’s being favoured by natural selection: a rare vindication of the so-called ‘hopeful monster’ theory that we met in Chapter 3.[17]

Donald R. Prothero in his book Evolution: What the Fossils Say and Why It Matters (2007) has written:

The past twenty years have vindicated Goldschmidt to some degree. With the discovery of the importance of regulatory genes, we realize that he was ahead of his time in focusing on the importance of a few genes controlling big changes in the organisms, not small-scales changes in the entire genome as neo-Darwinians thought. In addition, the hopeful monster problem is not so insurmountable after all. Embryology has shown that if you affect an entire population of developing embryos with a stress (such as a heat shock) it can cause many embryos to go through the same new pathway of embryonic development, and then they all become hopeful monsters when they reach reproductive age.[18]

In 2008 evolutionary biologist Olivia Judson in her article The Monster Is Back, and It’s Hopeful listed some examples which may support the hopeful monster hypothesis[19] and an article published in the nature journal in 2010 titled Evolution: Revenge of the Hopeful Monster reported that studies in stickleback populations in a British Columbia lake and bacteria populations in a Michigan lab have shown that large individual genetic changes can have vast effects on organisms "without dooming it to the evolutionary rubbish heap". According to the article "Single-gene changes that confer a large adaptive value do happen: they are not rare, they are not doomed and, when competing with small-effect mutations, they tend to win. But small-effect mutations still matter — a lot. They provide essential fine-tuning and sometimes pave the way for explosive evolution to follow."[20]

A paper by (Page et al. 2010) have written that the Mexican axolotl (Ambystoma mexicanum) could be classified as a hopeful monster as it exhibits an adaptive and derived mode of development that has evolved rapidly and independently among tiger salamanders. According to the paper there has been a recent interest in aspects of the hopeful monster hypothesis in recent years:

Goldschmidt proposed that mutations occasionally yield individuals within populations that deviate radically from the norm and referred to such individuals as "hopeful monsters". If the novel phenotypes of hopeful monsters arise under the right environmental circumstances, they may become fixed, and the population will found a new species. While this idea was discounted during the Modern synthesis, aspects of the hopeful monster hypothesis have been substantiated in recent years. For example, it is clear that dramatic changes in phenotype can occur from few mutations of key developmental genes and phenotypic differences among species often map to relatively few genetic factors. These findings are motivating renewed interest in the study of hopeful monsters and the perspectives they can provide about the evolution of development. In contrast to mutants that are created in the lab, hopeful monsters have been shaped by natural selection and are therefore more likely to reveal mechanisms of adaptive evolution.[21]

[edit] Evolutionary developmental biology

Goldschmidt presented two mechanisms for how hopeful monsters might work. One mechanism, involved “systemic mutations”, rejected the classical gene concept and is no longer considered by most modern scientists however, his second mechanism involved “developmental macromutations” in “rate genes” or “controlling genes” that change early development and thus cause large effects in the adult phenotype. These kind of mutations are similar to the ones considered in contemporary evolutionary developmental biology.[22]

[edit] Guenter Theissen

Guenter Theissen a professor of genetics has classified homeotic mutants as hopeful monsters and documented many examples for animal and plant lineages that may have originated as hopeful monsters in his scientific publications (Theissen, 2005 and Theissen et al. 2006).[23][24]

[edit] Creationist quote mining

Creationists are known for notoriously quote mining Goldschmidt, misrepresenting his views on purpose and for setting up a straw man definition of the hopeful monster. Thousands of creationist books since the 1960's have described the hopeful monster hypothesis as a bird hatching from a dinosaur egg or a reptile laying an egg with a bird popping out. The creationist Duane Gish was known for promoting this misrepresentation thoughout his books which he described as believing in a miracle.

In Abusing Science: The Case Against Creationism (1983) Philip Kitcher has discussed this issue, and wrote:

So far as I know, nobody is currently defending the idea that the birds evolved through the emergence of a single individual bird from a reptilian egg. The principal suggestion has been that some mutations - perhaps mutations in regulatory genes - might produce large effects by altering the timing of developmental events. By modifying the pattern of development, they could produce organisms with a different form from that of the parents.[25]

Unfortunately creationists out of dishonesty never choose to really study what Goldschmidt actually said and continue to peddle the lie that he promoted the view that birds popped out of reptile eggs. According to Stephen Jay Gould the scientist who speculated that the first bird may have hatched from a reptile's egg was Otto Schindewolf who linked cosmic radiation to mutational rates from supernova explosions.[26] Creationists have obviously confused the ideas of Goldschmidt with Schindewolf.

[edit] See also

[edit] External links

[edit] Footnotes

  1. Verne Grant The origin of adaptations 1963
  2. Prog Nucleic Acid Res&Molecular Bio by By J N Davidson, Waldo E. Cohn, Serge N Timasheff, C H Hirs 1968, p. 67
  3. Nick Lane Power, Sex, Suicide : Mitochondria and the meaning of life 2005, p. 30
  4. Eva Jablonka, Marion J. Lamb Epigenetic Inheritance and Evolution: The Lamarckian Dimension 1995 p. 222
  5. Donald R. Prothero Evolution: What the Fossils Say and Why It Matters 2007, p. 99
  6. Chunglin Kwa Styles of Knowing: A New History of Science from Ancient Times to the Present 2011, p. 237
  7. Book Review
  8. David H. Levy Shoemaker by Levy: The Man Who Made an Impact 2002, p. 61
  9. Trevor Palmer Perilous Planet Earth: Catastrophes and Catastrophism through the Ages 2003, p.99
  10. Otto Schindewolf Über den “Typus” in morphologischer und phylogenetischer Biologie. Mainz: Akademie der Wissenschaften und der Literatur, 1969
  11. New Scientist 15 Apr 1982
  12. Return of the Hopeful Monster by Stephen Jay Gould
  13. Stephen T. Asma On Monsters: An Unnatural History of Our Worst Fears 2011, p. 314
  14. Peter J. Bowler Evolution: The History of an Idea 1989 p. 340
  15. Donald R Prothero Evolution: What the Fossils Say and Why It Matters 2007, p. 99
  16. Patrick Baeson Sudden Changes in Ontogeny and Phylogeny in Gary Greenberg, Ethel Tobach Behavioral Evolution and Integrative Levels: The T.C. Schneirla Series 1984, p. 162
  17. Richard Dawkins Climbing Mount Improbable 1996, pp. 232-233
  18. Donald R Prothero Evolution: What the Fossils Say and Why It Matters 2007, p. 100
  19. The Monster Is Back, and It’s Hopeful by Olivia Judson
  20. Evolution: Revenge of the hopeful monster by Tanguy Chouard
  21. Microarray analysis of a salamander hopeful monster reveals transcriptional signatures of paedomorphic brain development
  22. Homeosis of the angiosperm flower: Studies on three candidate cases of saltational evolution
  23. The proper place of hopeful monsters in evolutionary biology
  24. Catching a ‘hopeful monster’: shepherd’s purse (Capsellabursa-pastoris) as a model system to study the evolution of flower development
  25. Philip Kitcher Abusing Science: The Case Against Creationism 1983, p. 149
  26. Basic Questions in Paleontology
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