Macromutation Theory
The German geneticist Richard Goldschmidt 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.
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. 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.
Otto Schindewolf 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 but abandoned the view of macromutations in later publications.
Soren Lovtrup advocated a similar hypothesis of macromutation to Goldschmidt's in 1974. Lovtrup, a biochemist and embryologist from Denmark, believed that macromutations interfered with various epigenetic processes, that is, those which affect the casual processes in biological development. This is in contrast to the gradualistic theory of micromutations of Neo-Darwinism which claims that evolutionary innovations are generally the result of accumulation of numerous very slight modifications. Lovtrup also rejected the punctuated equilibria of Stephen Gould and Niles Eldredge claiming it was a form of gradualism and not a macromutation theory. Lovtrup defended many of Darwin's critics including Schindewolf, Mivart, Goldschmidt, and Himmelfarb. Mae Wan Ho described Lovtrup's theory as similar to the hopeful monster theory of Richard Goldschmidt.
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 modern science 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.
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 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."
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 an 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. | ” |
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).
Read more about this topic: Saltation (biology)
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