{{Short description|One of several alternatives to evolution by natural selection}} {{good article}} [[File:Hugo de Vries (1848-1935), by Thérèse Schwartze (1851-1918).jpg|thumb|upright=1.5|Painting of [[Hugo de Vries]], making a painting of an [[Oenothera|evening primrose]], the plant which had apparently produced new forms by large mutations in his experiments, by [[Thérèse Schwartze]], 1918]] '''Mutationism''' is one of several [[alternatives to evolution by natural selection]] that have existed both before and after the publication of [[Charles Darwin]]'s 1859 book ''[[On the Origin of Species]]''. In the theory, mutation was the source of novelty, creating new forms and new species, potentially instantaneously,<ref name=BowlerEclipse/> in sudden jumps.{{sfn|Smocovitis|1996|p=56}} This was envisaged as driving evolution, which was thought to be limited by the supply of mutations.
Before Darwin, biologists commonly believed in [[saltationism]], the possibility of large evolutionary jumps, including immediate [[speciation]]. For example, in 1822 [[Étienne Geoffroy Saint-Hilaire]] argued that species could be formed by sudden transformations, or what would later be called macromutation. Darwin opposed saltation, insisting on [[phyletic gradualism|gradualism]] in evolution as [[uniformitarianism|geology's uniformitarianism]]. In 1864, [[Albert von Kölliker]] revived Geoffroy's theory. In 1901 the [[geneticist]] [[Hugo de Vries]] gave the name "mutation" to seemingly new forms that suddenly arose in his experiments on the evening primrose ''[[Oenothera lamarckiana]]''. In the first decade of the 20th century, mutationism, or as de Vries named it '''''mutationstheorie''''', became a rival to Darwinism supported for a while by geneticists including [[William Bateson]], [[Thomas Hunt Morgan]], and [[Reginald Punnett]].
Understanding of mutationism is clouded by the mid-20th century portrayal of the early mutationists by supporters of the [[Modern synthesis (20th century)|modern synthesis]] as opponents of Darwinian evolution and rivals of the biometrics school who argued that selection operated on continuous variation. In this portrayal, mutationism was defeated by a synthesis of genetics and natural selection that supposedly started later, around 1918, with work by the mathematician [[Ronald Fisher]]. However, the alignment of Mendelian genetics and natural selection began as early as 1902 with a paper by [[Udny Yule]], and built up with theoretical and experimental work in Europe and America. Despite the controversy, the early mutationists had by 1918 already accepted natural selection and explained continuous variation as the result of multiple genes acting on the same characteristic, such as height.
Mutationism, along with other alternatives to Darwinism like [[Lamarckism]] and [[orthogenesis]], was discarded by most biologists as they came to see that [[Modern synthesis (20th century)|Mendelian genetics and natural selection could readily work together]]; mutation took its place as a source of the genetic variation essential for natural selection to work on. However, mutationism did not entirely vanish. In 1940, [[Richard Goldschmidt]] again argued for single-step speciation by macromutation, describing the organisms thus produced as "hopeful monsters", earning widespread ridicule. In 1987, [[Masatoshi Nei]] argued controversially that evolution was often mutation-limited. Modern biologists such as [[Douglas J. Futuyma]] conclude that essentially all claims of evolution driven by large mutations can be explained by Darwinian evolution.
== Developments leading up to mutationism == [[File:Geoffroy72.jpg|thumb|upright|[[Étienne Geoffroy Saint-Hilaire]] believed that "monstrosities" could immediately found new species in a single large jump or [[saltation (biology)|saltation]].]]
=== Geoffroy's monstrosities, 1822 === {{Further|Saltationism}}
Prior to [[Charles Darwin]], most naturalists were [[saltationism|saltationists]],{{efn|The term mutation was not used in biology until the 20th century, but [[macromutation]] and saltation are essentially equivalent descriptions.<ref>{{cite book|last1=Dawkins |first1=Richard |author-link1=Richard Dawkins |title=Unweaving the Rainbow |date=1999 |orig-date=1998 |publisher=Penguin |isbn=978-0-14-026408-1 |page=195}}</ref>}} believing that species evolved and that [[speciation]] took place in sudden jumps.<ref>{{cite book |last=Osborn |first=Henry Fairfield |author-link=Henry Fairfield Osborn |year=1894 |title=From the Greeks to Darwin: An outline of the development of the evolution idea |publisher=Macmillan |pages=[https://archive.org/details/fromgreekstodar00osbogoog/page/n244 228]–250 |url=https://archive.org/details/fromgreekstodar00osbogoog}}</ref> [[Jean-Baptiste Lamarck]] was a gradualist but similar to other scientists of the period had written that saltational evolution was possible.{{sfn|Bowler|1989|p=83}}
In 1822, in the second volume of his ''Philosophie anatomique'', [[Étienne Geoffroy Saint-Hilaire]] endorsed a theory of saltational evolution that "monstrosities could become the founding fathers (or mothers) of new species by instantaneous transition from one form to the next."<ref>{{cite book |last1=Hallgrímsson |first1=Benedikt |last2=Hall |first2=Brian K. |year=2011 |title=Variation: A Central Concept in Biology |url=https://archive.org/details/variationcentral00hall |url-access=limited |publisher=Academic Press |isbn=978-0-12-088777-4 |page=[https://archive.org/details/variationcentral00hall/page/n22 18]}}</ref> Geoffroy wrote that environmental pressures could produce sudden transformations to establish new [[species]] instantaneously.{{sfn|Bowler|2003|p=127}}
=== Darwin's anti-saltationist gradualism, 1859 === {{Further|Phyletic gradualism}}
In his 1859 book ''[[On the Origin of Species]]'', [[Charles Darwin]] denied saltational evolution. He argued that evolutionary transformation always proceeds gradually, never in jumps: "[[natural selection]] acts solely by accumulating slight successive favourable variations, it can produce no great or sudden modification; it can act only by very short steps". Darwin continued in this belief throughout his life.<ref>{{cite book |last=Darwin |first=Charles |author-link=Charles Darwin |year=1859 |title=On the Origin of Species |page=471 |url=http://darwin-online.org.uk/converted/pdf/1859_Origin_F373.pdf}}</ref>
[[File:Kölliker Rudolph Albert von 1818-1902.jpg|thumb|upright|Rudolph Albert von Kölliker revived Geoffroy's saltationist ideas, calling his theory [[heterogenesis]]. It depended on a nonmaterial directive force ([[orthogenesis]]).]]
[[Thomas Henry Huxley]] warned Darwin that he had taken on "an unnecessary difficulty in adopting ''[[Natura non facit saltus|Natura non facit saltum]]'' ["Nature does not take leaps"] so unreservedly."<ref>[[Thomas Henry Huxley]]. (1859). [http://www.darwinproject.ac.uk/darwinletters/calendar/entry-2544.html Letter to Charles Darwin.] {{Webarchive|url=https://web.archive.org/web/20080131230929/http://www.darwinproject.ac.uk/darwinletters/calendar/entry-2544.html |date=2008-01-31 }} Nov. 23, 1859.</ref> Huxley feared this assumption could discourage naturalists ([[catastrophism|catastrophists]]) who believed that major leaps and cataclysms played a significant role in the history of life.<ref name=gould77>{{cite journal |last=Gould |first=Stephen J. |author-link=Stephen Jay Gould |year=1977 |url=http://www.stephenjaygould.org/library/gould_hopeful-monsters.html |title=The Return of Hopeful Monsters |journal=Natural History |volume=86 |issue=24 |page=30}}</ref>
=== von Kölliker's heterogenesis, 1864 ===
In 1864 [[Albert von Kölliker]] revived Geoffroy's theory that evolution proceeds by large steps, under the name of [[heterogenesis]], but this time assuming the influence of a nonmaterial force{{efn|[[Orthogenesis]], possibly [[vitalism]].}} to [[Orthogenesis|direct the course of evolution]].<ref>{{cite book |last=Wright |first=Sewall |author-link=Sewall Wright |year=1984 |title=Evolution and the Genetics of Populations: Genetics and Biometric Foundations Volume 1 |publisher=University of Chicago Press |page=[https://archive.org/details/evolutiongenetic0003wrig_b9l5/page/10 10] |isbn=978-0-226-91038-3 |url=https://archive.org/details/evolutiongenetic0003wrig_b9l5/page/10 }}</ref><ref>{{harvnb|Provine|2001|p=24}}</ref>
=== Galton's "sports", 1892 ===
Darwin's cousin, [[Francis Galton]], considered Darwin's evidence for evolution, and came to an opposite conclusion about the type of variation on which natural selection must act. He carried out his own experiments and published a series of papers and books setting out his views. Already by 1869 when he published ''Hereditary Genius'', he believed in evolution by saltation. In his 1889 book ''Natural Inheritance'' he argued that natural selection would benefit from accepting that the steps need not, as Darwin had stated, be minute. In his 1892 book ''Finger Prints'', he stated directly that "The progress of evolution is not a smooth and uniform progression, but one that proceeds by jerks, through successive 'sports' (as they are called), some of them implying considerable organic changes; and each in its turn being favoured by Natural Selection".<ref>{{harvnb|Provine|2001|pp=14–24}}</ref>
From 1860 to 1880 saltation had been a minority viewpoint, to the extent that Galton felt his writings were being universally ignored. By 1890 it became a widely held theory, and his views helped to launch a major controversy.<ref>{{cite book |last=Radick |first=Gregory |year=2008 |title=The Simian Tongue: The Long Debate about Animal Language |publisher=University Of Chicago Press |page=[https://archive.org/details/simiantonguelong00radi/page/368 368] |isbn=978-0-226-70224-7 |url-access=registration |url=https://archive.org/details/simiantonguelong00radi/page/368 }}</ref><ref name="LevitMeister2008">{{cite journal |last1=Levit |first1=Georgy S. |last2=Meister |first2=Kay |last3=Hoßfeld |first3=Uwe |title=Alternative evolutionary theories: A historical survey|journal=Journal of Bioeconomics |volume=10 |issue=1 |year=2008 |pages=71–96 |doi=10.1007/s10818-008-9032-y|s2cid=145540549 }}</ref> [[File:Bateson@72 (detail).jpg|thumb|upright|Drawing of [[William Bateson]], 1909, by the biologist [[Dennis G. Lillie]]]]
=== Bateson's discontinuous variation, 1894 ===
[[William Bateson]]'s 1894 book ''Materials for the Study of Variation, Treated with Especial Regard to Discontinuity in the Origin of Species'' marked the arrival of mutationist thinking, before the rediscovery of Mendel's laws.<ref name=Bateson1894>{{cite book |last=Bateson |first=William |author-link=William Bateson |year=1894 |title=Materials for the Study of Variation, Treated with Especial Regard to Discontinuity in the Origin of Species |publisher=Macmillan |url=https://archive.org/stream/materialsforstud00bate#page/n5/mode/2up}}</ref> He examined discontinuous variation (implying a form of saltation<ref name=Gillham2001>{{cite journal |last1=Gillham |first1=Nicholas W. |title=Evolution by Jumps: Francis Galton and William Bateson and the Mechanism of Evolutionary Change |journal=Genetics|date=December 2001 |volume=159 |issue=4 |pages=1383–1392 |doi=10.1093/genetics/159.4.1383 |pmid=11779782 |pmc=1461897 |url=http://www.genetics.org/content/159/4/1383.full}}</ref>) where it occurred naturally, following [[William Keith Brooks]], Galton, [[Thomas Henry Huxley]] and [[St. George Jackson Mivart]].<ref name=Gillham2001/>
== Early 20th century mutationism ==
=== De Vries and Mendelian ''mutationstheorie'', 1901 === {{Further|Hugo de Vries|Alternatives to Darwinism}} {{quote|The main principle of the mutation theory is that species and varieties have originated by mutation, but are, at present, not known to have originated in any other way. — Hugo de Vries<ref>{{cite book |last=De Vries |first=Hugo |author-link=Hugo de Vries |chapter=Age and Area and the Mutation Theory |editor=Willis, J. C. |editor-link=John Christopher Willis |title=Age and Area. A Study in Geographical Distribution and Origin of Species |year=1922 |publisher=Cambridge University Press |page=[https://archive.org/details/ageareastudyinge00will/page/222 222] |url=https://archive.org/details/ageareastudyinge00will}}</ref>}}
[[Hugo de Vries]]'s careful 1901 studies of wild variants of the evening primrose ''[[Oenothera lamarckiana]]'' showed that distinct new forms could arise suddenly in nature, apparently at random, and could be propagated for many generations without dissipation or blending. He gave such changes the name "[[mutation]]".{{efn|The changes in the evening primrose were later shown to be caused by chromosome duplications ([[polyploidy]]) rather than gene mutation.{{sfn|Endersby|2007|pp=202–205}}}}<ref name=DeVries1901-1903>{{cite book |last=De Vries |first=Hugo |author-link=Hugo de Vries |year=1901–1903 |title=Die mutationstheorie. Vol I and II |trans-title=The Mutation Theory |publisher=Von Veit, Leipzig |url=https://archive.org/stream/diemutationstheo11901vrie#page/n5/mode/1up}} [https://archive.org/details/diemutationstheo02vrie Part 2, 1903]</ref><ref>{{cite journal |last=De Vries |first=Hugo |author-link=Hugo de Vries |date=January 1919 |title=Oenothera rubrinervis; A Half Mutant |journal=Botanical Gazette |volume=67 |issue=1 |pages=1–26 |jstor=2468868 |doi=10.1086/332396|s2cid=83752035 |url=https://zenodo.org/record/1431405 }}</ref> By this, de Vries meant that a new form of the plant was created in a single step (not the same as a mutation in the modern sense); no long period of natural selection was required for speciation, and nor was [[reproductive isolation]].{{sfn|Bowler|2003|p=276}} In the view of the historian of science [[Peter J. Bowler]], De Vries used the term to mean<ref name=BowlerEclipse>{{cite book |last=Bowler |first=Peter J. |author-link=Peter J. Bowler |title=The Eclipse of Darwinism |date=1992 |orig-date=1983 |isbn=978-0-8018-4391-4 |page=198|publisher=JHU Press }}</ref>
{{quote|large-scale genetic changes capable of producing a new subspecies, or even species, instantaneously.<ref name=BowlerEclipse/>}}
The historian of science Betty Smocovitis described mutationism as:{{sfn|Smocovitis|1996|p=56}}
{{quote|the case of purported [[saltationism|saltatory evolution]] that Hugo de Vries had mistakenly interpreted for the evening primrose, ''[[Oenothera]]''.{{sfn|Smocovitis|1996|p=56}}}}
De Vries set out his position, known as ''Mutationstheorie'' (mutation theory) on the creative nature of mutation in his 1905 book ''Species and Varieties: their Origin by Mutation''.<ref name=DeVries1905>{{cite book |last=De Vries |first=Hugo |author-link=Hugo de Vries |year=1905 |title=Species and Varieties: Their Origin by Mutation |publisher=The Open Court Publishing Company, Chicago |url=https://www.biodiversitylibrary.org/item/16221#page/11/mode/1up}}</ref> In the view of the historian of science Edward Larson, de Vries was the person largely responsible for transforming Victorian era saltationism into early 20th century mutation theory, "and in doing so pushed Darwinism near the verge of extinction as a viable scientific theory".{{sfn|Larson|2004|p=128}}
Similar ideas were propounded in [[Imperial Russia]], even before De Vries, by [[Sergey Korzhinsky]].<ref>[[Georgy Plekhanov]]. ''Fundamental Problems of Marxism''. New York: International Publishers, 1928. P. 139-140.</ref><ref>{{cite book | url=https://books.google.com/books?id=NV5HcU9B2kQC&pg=PA210 | title=The Evolutionary Synthesis: Perspectives on the Unification of Biology | isbn=978-0-674-27226-2 | last1=Mayr | first1=Ernst | last2=Provine | first2=William B. | date=1998 | publisher=Harvard University Press }}</ref>
=== Johannsen's "pure line" experiments, 1903=== [[File:Wilhelm Johannsen 1857-1927.jpg|thumb|upright|[[Wilhelm Johannsen]]'s "pure line" experiments seemed to show that evolution could not work on continuous variation.]]
In the early 1900s, Darwin's mechanism of natural selection was understood by believers in continuous variation, principally the [[biometrician]]s [[Walter Weldon]] and [[Karl Pearson]], to be able to work on a continuously varying characteristic, whereas de Vries argued that selection on such characteristics would be ineffective. [[Wilhelm Johannsen]]'s "pure line" experiments on ''[[Phaseolus vulgaris]]'' beans appeared to refute this mechanism. Using the true-breeding Princess variety of bean, carefully inbred within weight classes, Johannsen's work appeared to support de Vries. The offspring had a smooth random distribution. Johanssen believed that his results showed that continuous variability was not inherited, so evolution must rely on discontinuous mutations, as de Vries had argued.{{sfn|Provine|2001|pp=92–100}}<ref name=Roll-Hansen_1989>{{cite journal |last=Roll-Hansen |first=N. |year=1989 |title=The crucial experiment of Wilhelm Johannsen |journal=Biology and Philosophy |volume=4 |issue=3 |pages=303–329 |doi=10.1007/bf02426630|s2cid=170325857 }}</ref><ref name=Richmond_2006>{{cite journal |last=Richmond |first=M. L. |year=2006 |title=The 1909 Darwin celebration. Reexamining evolution in the light of Mendel, mutation, and meiosis |journal=Isis |volume=97 |issue=3 |pages=447–484 |doi=10.1086/508076|pmid=17059108 |s2cid=24783737 }}</ref>{{sfn|Bowler|2003|pp=265–270}} Johanssen published his work in Danish in a 1903 paper ''Om arvelighed i samfund og i rene linier'' (On inheritance in populations and in pure lines),<ref>Johannsen, W. (1903) "Om arvelighed i samfund og i rene linier". ''Oversigt over det [[Kongelige Danske Videnskabernes Selskab]]s Forhandlinger'', vol. 3: 247–270 (in Danish). German ed. ''Erblichkeit in Populationen und in reinen Linien'' [On inheritance in populations and in pure lines] (1903) Gustav Fischer, Jena. [http://caliban.mpiz-koeln.mpg.de/~stueber/johannsen/erblichkeit/index.html Scanned full text.] {{Webarchive|url=https://web.archive.org/web/20090530140510/http://caliban.mpiz-koeln.mpg.de/~stueber/johannsen/erblichkeit/index.html |date=2009-05-30 }}</ref> and in his 1905 book ''Arvelighedslærens Elementer'' (The Elements of Heredity).<ref>{{cite book |last=Johannsen |first=W. L. |year=1905 |title=Arvelighedslærens elementer |trans-title=The elements of heredity |language=da |url=https://books.google.com/books?id=1FI3AQAAMAAJ}}</ref>
=== Punnett's mimicry, 1915 === [[File:Common Mormon Papilio polytes Female Form Romulus by kadavoor.jpg|thumb|''[[Papilio polytes]]'' has 3 forms with differing wing patterns, here the "Romulus" morph. [[Reginald Punnett]] argued that this [[polymorphism (biology)|polymorphism]] demonstrated discontinuous evolution. However, [[Ronald Fisher]] showed that this could have arisen by small changes in additional modifier genes.]]
In 1915, [[Reginald Punnett]] argued in his book ''Mimicry in Butterflies'' that the 3 morphs (forms) of the butterfly ''[[Papilio polytes]]'', which [[mimicry|mimic]] different host species of butterfly, demonstrated discontinuous evolution in action. The different forms existed in a stable [[polymorphism (biology)|polymorphism]] controlled by 2 Mendelian factors ([[gene]]s). The alleles of these genes were certainly discontinuous, so Punnett supposed that they must have evolved in discontinuous leaps.<ref>{{cite book |last=Punnett |first=Reginald C. |author-link1=Reginald Punnett |title=Mimicry in Butterflies |date=1915 |publisher=Cambridge University Press |url=https://archive.org/details/mimicryinbutterf00punn}}</ref>
== The undermining of mutationism ==
=== Yule's analysis of Mendelism and continuous variation, 1902 ===
The undermining of mutationism began almost at once, in 1902, as the statistician [[Udny Yule]] analysed Mendel's theory and showed that given full dominance of one allele over another, a 3:1 ratio of alleles would be sustained indefinitely. This meant that the recessive allele could remain in the population with no need to invoke mutation. He also showed that given multiple factors, Mendel's theory enabled continuous variation, as indeed Mendel had suggested, removing the central plank of the mutationist theory, and criticised Bateson's confrontational approach.<ref>{{Cite journal |last=Yule |first=G. Udny |author-link=Udny Yule |title=Mendel's Laws and their probable relations to inter-racial heredity |url=http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1902.tb06590.x/pdf |journal=[[New Phytologist]] |volume=1 |issue=10 |pages=226–227 |date=1902 |doi=10.1111/j.1469-8137.1902.tb07336.x|doi-access=free |bibcode=1902NewPh...1..222Y }}</ref> However, the "excellent"{{sfn|Provine|2001|pp=81–82}} paper did not prevent the [[Mutationism-biometrics debate|Mendelians and the biometricians]] from falling out.{{sfn|Provine|2001|pp=81–82}}
=== Nilsson-Ehle's experiments on Mendelian inheritance and continuous variation, 1908 ===
The Swedish geneticist [[Herman Nilsson-Ehle|H. Nilsson-Ehle]] demonstrated in 1908, in a paper published in German in a Swedish journal, ''Einige Ergebnisse von Kreuzungen bei Hafer und Weizen'' (Observations on Crosses in Oats and Wheat),<ref>{{cite journal |last1=Nilsson-Ehle |first1=H. |title=Einige Ergebnisse von Kreuzungen bei Hafer und Weizen |language=de |trans-title=Observations on Crosses in Oats and Wheat |journal=Botaniska Notiser |date=1908 |pages=257–294 |url=http://echo.mpiwg-berlin.mpg.de/ECHOdocuView?url=/permanent/vlp/lit38177/index.meta}}</ref> that continuous variation could readily be produced by multiple Mendelian genes. He found numerous Mendelian 3:1 ratios, implying a dominant and a recessive allele, in [[oats]] and [[wheat]]; a 15:1 ratio for a cross of oat varieties with black and white [[glume]]s respectively, implying two pairs of alleles (two Mendelian factors); and that crossing a red-grained Swedish velvet wheat with a white one gave in the third (F3) generation the complex signature of ratios expected of three factors at once, with 37 grains giving only red offspring, 8 giving 63:1 in their offspring, 12 giving 15:1, and 6 giving 3:1. There weren't any grains giving all white, but as he had only expected 1 of those in his sample, 0 was not an unlikely outcome. Genes could clearly combine in almost infinite combinations: ten of his factors allowed for almost 60,000 different forms, with no need to suppose that any new mutations were involved. The results implied that natural selection would work on Mendelian genes, helping to bring about the unification of Darwinian evolution and genetics.{{sfn|Provine|2001|pp=114–118}}
Similar work in America by [[Edward Murray East|Edward East]] on [[maize]] in 1910<ref>{{cite journal |last1=East |first1=Edward |title=A Mendelian Interpretation of Variation that is Apparently Continuous |journal=American Naturalist |date=1910 |volume=44 |issue=518 |pages=65–82 |jstor=2455657 |doi=10.1086/279117|bibcode=1910ANat...44...65E |s2cid=85340555 |url=https://zenodo.org/record/1431353 }}</ref> showed the same thing for biologists without access to Nilsson-Ehle's work.{{sfn|Provine|2001|pp=118–120}} On the same theme, the mathematician [[Ronald Fisher]] published "[[The Correlation Between Relatives on the Supposition of Mendelian Inheritance]]" in 1918,<ref>{{cite journal |title=The Correlation Between Relatives on the Supposition of Mendelian Inheritance |first1=Ronald A. |last1=Fisher |journal=Transactions of the Royal Society of Edinburgh |year=1918 |volume=52 |issue=2 |pages=399–433 |doi=10.1017/s0080456800012163|s2cid=181213898 |url=https://zenodo.org/record/1428666 }}</ref> again showing that continuous variation could readily be produced by multiple Mendelian genes. It showed, too, that Mendelian inheritance had no essential link with mutationism: Fisher stressed that small variations (per gene) would be sufficient for natural selection to drive evolution.<ref name=ProvineOnFisher>{{harvnb|Provine|2001|pp=140–154}}</ref>
=== Castle's selection experiments on hooded rats, 1911 ===
Starting in 1906, [[William E. Castle|William Castle]] carried out a long study of the effect of selection on coat colour in [[rat]]s. The [[piebald]] or hooded pattern was recessive to the grey [[wild type]]. He crossed hooded rats with the black-backed Irish type, and then back-crossed the offspring with pure hooded rats. The dark stripe on the back was bigger. He then tried selecting different groups for bigger or smaller stripes for 5 generations, and found that it was possible to change the characteristics way beyond the initial range of variation. This effectively refuted de Vries's claim that continuous variation could not be inherited permanently, requiring new mutations. By 1911 Castle noted that the results could be explained by Darwinian selection on heritable variation of Mendelian genes.{{sfn|Provine|2001|pp=109–114}}
=== Morgan's small Mendelian genes in ''Drosophila'', 1912 === [[File:Drosophila melanogaster - side (aka).jpg|thumb|[[Thomas Hunt Morgan]]'s work on ''[[Drosophila melanogaster]]'' found many small Mendelian factors for natural selection to work on.]]
By 1912, after years of work on the genetics of ''[[Drosophila]]'' fruit flies, [[Thomas Hunt Morgan]] showed that these animals had many small Mendelian factors on which Darwinian evolution could work as if variation was fully continuous. The way was open for geneticists to conclude that Mendelism supported Darwinism.{{sfn|Provine|2001|pp=120–121}}{{sfn|Allen|1968|pp=113–139}}
=== Muller's balanced lethal explanation of ''Oenothera'' "mutations", 1918 ===
De Vries's mutationism was dealt a serious if not fatal blow in 1918 by the American geneticist [[Hermann Joseph Muller]]. He compared the behaviour of balanced lethals in ''Drosophila'' with De Vries's supposed mutations in ''Oenothera'', showing that they could work the same way.<ref>{{cite journal |last1=Muller |first1=Hermann Joseph |title=Genetic Variability, Twin Hybrids and Constant Hybrids, in a Case of Balanced Lethal Factors |journal=Genetics |date=1918 |volume=2 |issue=5 |pages=422–99 |doi=10.1093/genetics/3.5.422 |pmc=1200446 |pmid=17245914}}</ref> No actual mutations were involved, but infrequent [[chromosome]] crossovers accounted for the sudden appearance of traits which had been present in the genes all along.{{sfn|Provine|2001|pp=121–122}}
=== Fisher's explanation of polymorphism, 1927 ===
In 1927, Fisher explicitly attacked Punnett's 1915 theory of discontinuous evolution of mimicry. Fisher argued that selection acting on genes making small modifications to the butterfly's [[phenotype]] (its appearance) would allow the multiple forms of a polymorphism to be established.<ref name=ProvineOnFisher/>
== Later mutationist theories == The understanding that Mendelian genetics could both preserve discrete variations indefinitely, and support continuous variation for natural selection to work on gradually, meant that most biologists from around 1918 onwards accepted natural selection as the driving force of evolution.{{sfn|Bowler|2003|pp=307–308}} Mutationism and other alternatives to evolution by natural selection did not however vanish entirely.<ref name=Levit/><ref name=Hubbs/><ref name=Gould1982/>
=== Berg's nomogenesis, 1922 ===
[[Lev Berg]] proposed a combination of mutationism and directed (orthogenetic) evolution in his 1922 book ''[[Nomogenesis]]; or, Evolution Determined by Law''. He used evidence from [[paleontology]], [[zoology]], and [[botany]] to argue that natural selection had limitations which set a direction for evolution. He claimed that speciation was caused by "mass transformation of a great number of individuals" by directed mass mutations.<ref>{{cite journal |last=Berg |first=Lev |author-link=Lev Berg |year=1969 |title=Nomogenesis; or, Evolution Determined by Law |journal=Science |volume=164 |issue=3880 |pages=684–685 |publisher=M.I.T. Press |orig-date=1922 |doi=10.1126/science.164.3880.684 |url=https://www.science.org/doi/10.1126/science.164.3880.684|url-access=subscription }}</ref><ref name=Levit>{{cite journal |last1=Levit |first1=Georgy S. |last2=Olsson |first2=Lennart |title='Evolution on Rails': Mechanisms and Levels of Orthogenesis |journal=Annals of the History and Philosophy of Biology |issue=11 |year=2006 |pages=112–113 |url=https://www.univerlag.uni-goettingen.de/bitstream/handle/3/isbn-978-3-938616-85-7/annals%2011_DGGBT.pdf?sequence=1&isAllowed=y}}</ref>
[[File:The course of evolution by differentiation or divergent mutation rather than by selection (1940) (20709042401).jpg|thumb|upright=1.35|[[John Christopher Willis]]'s ''The Course of Evolution by Differentiation Or Divergent Mutation Rather Than by Selection'', 1940]]
=== Willis's macromutations, 1923 === {{Further|Orthogenesis}}
In 1923, the botanist [[John Christopher Willis]] proposed that species were formed by large mutations, not gradual evolution by natural selection,<ref>{{cite journal |author-link=John Christopher Willis |last=Willis |first=J. C. |year=1923 |title=The Origin of Species by Large, rather than by Gradual, Change, and by Guppy's Method of Differentiation |journal=Annals of Botany |volume=37 |issue=148 |pages=605–628|doi=10.1093/oxfordjournals.aob.a089870 }}</ref><ref>{{cite journal |last=Beal |first=J. M. |year=1941 |title=The Course of Evolution by J. C. Willis |journal=Botanical Gazette |volume=102 |issue=3 |page=638 |doi=10.1086/334994}}</ref> and that evolution was driven by [[orthogenesis]], which he called "differentiation", rather than by natural selection.<ref name=Hubbs>{{cite journal |last=Hubbs |first=Carl L. |author-link=Carl L. Hubbs |title=The Course of Evolution by J. C. Willis. Review |journal=The American Naturalist |volume=76 |issue=762 |date=1942 |pages=96–101 |doi=10.1086/281018}}</ref>
=== Goldschmidt's hopeful monsters, 1940 ===
[[File:Masatoshi Nei - 2013.jpg|thumb|upright|[[Masatoshi Nei]] argues that evolution is often mutation-limited.<ref name=Stoltzfus_on_Nei2014/>]]
In his 1940 book ''The Material Basis of Evolution'', the German geneticist [[Richard Goldschmidt]] argued for single-step speciation by macromutation, describing the organisms thus produced as "hopeful monsters". Goldschmidt's thesis was universally rejected and widely ridiculed by biologists, who favoured the [[neo-Darwinism|neo-Darwinian]] explanations of Fisher, [[J. B. S. Haldane]] and [[Sewall Wright]].<ref name=Gould1982>{{cite book |author-link=Stephen Jay Gould |last=Gould |first=Stephen J. |year=1982 |title=The uses of heresy; an introduction to Richard Goldschmidt's ''The Material Basis of Evolution'' |url=https://books.google.com/books?id=kAPLvAnp7KAC&pg=PR13 |pages=xiii–xlii |publisher=Yale University Press |isbn=978-0-300-02823-2}}</ref>{{sfn|Ruse|1996|pp=412–413}} However, interest in Goldschmidt's ideas has reawakened in the field of [[evolutionary developmental biology]].<ref>{{cite journal |last=Theissen |first=Guenter |year=2010 |url=http://www.palaeodiversity.org/pdf/03Suppl/Supplement_Theissen.pdf |title=Homeosis of the angiosperm flower: Studies on three candidate cases of saltational evolution |journal=Palaeodiversity |volume=3 |issue=Supplement |pages=131–139}}</ref><ref name="KutscheraNiklas2008">{{cite journal |last1=Kutschera |first1=U. |last2=Niklas |first2=K. J. |title=Macroevolution via secondary endosymbiosis: a Neo-Goldschmidtian view of unicellular hopeful monsters and Darwin's primordial intermediate form |journal=Theory in Biosciences |volume=127 |issue=3 |year=2008 |pages=277–289 |doi=10.1007/s12064-008-0046-8|pmid=18581157 |s2cid=13372946 }}</ref><ref>[[Olivia Judson|Judson, Olivia]]. (2008). [http://opinionator.blogs.nytimes.com/2008/01/22/the-monster-is-back-and-its-hopeful/ ''The Monster Is Back, and It's Hopeful'']. ''[[The New York Times]]''.</ref><ref name="Chouard2010">{{cite journal |last1=Chouard |first1=Tanguy |title=Evolution: Revenge of the hopeful monster |journal=Nature |volume=463 |issue=7283 |year=2010 |pages=864–867 |doi=10.1038/463864a|pmid=20164895 |doi-access=free }}</ref><ref name="PageBoley2010">{{cite journal |last1=Page |first1=Robert B. |last2=Boley |first2=Meredith A. |last3=Smith |first3=Jeramiah J. |last4=Putta |first4=Srikrishna |last5=Voss |first5=Stephen R. |title=Microarray analysis of a salamander hopeful monster reveals transcriptional signatures of paedomorphic brain development |journal=BMC Evolutionary Biology |volume=10 |issue=1 |year=2010 |page=199 |doi=10.1186/1471-2148-10-199|pmid=20584293 |pmc=2900274 |doi-access=free |bibcode=2010BMCEE..10..199P }}</ref>
=== Nei's mutation-driven evolution, 1987 ===
Contemporary biologists accept that mutation and selection both play roles in evolution; the mainstream view is that while mutation supplies material for selection in the form of variation, all non-random outcomes are caused by natural selection.<ref name=Wagner_2013>{{cite journal |last=Wagner |first=G. P. |date=1 January 2013 |title=The Changing Face of Evolutionary Thinking |journal=Genome Biology and Evolution |volume=5 |issue=10 |pages=2006–2007 |doi=10.1093/gbe/evt150|pmc=3814208 }}</ref> [[Masatoshi Nei]] argues instead that the production of more efficient genotypes by mutation is fundamental for evolution, and that evolution is often mutation-limited.<ref name=Stoltzfus_on_Nei2014>{{cite journal |last=Stoltzfus |first=Arlin |year=2014 |title=In search of mutation-driven evolution |journal=Evolution & Development |volume=16 |pages=57–59 |doi=10.1111/ede.12062}}</ref><ref>{{cite journal |last=Takahata |first=N. |year=2007 |title=Molecular Clock: An Anti-neo-Darwinian Legacy |journal=Genetics |volume=176 |issue=1 |pages=1–6 |doi=10.1534/genetics.104.75135 |pmid=17513888 |quote=Unlike neo-Darwinism, which regards mutation as merely raw material and natural selection as the creative power, Nei's mutationism assumes that the most fundamental process for adaptive evolution is the production of functionally more efficient genotypes by mutation (especially birth and death of duplicated genes) and by recombination.|pmc=1893057 }}</ref><ref>Nei's works on this topic include: * {{cite book |last=Nei |first=Masatoshi |author-link=Masatoshi Nei |year=1984 |chapter=Genetic Polymorphism and Neomutationism |volume=53 |editor=G. S. Mani |title=Evolutionary Dynamics of Genetic Diversity |pages=214–241 |publisher=Springer |doi=10.1007/978-3-642-51588-0|series=Lecture Notes in Biomathematics |isbn=978-3-540-12903-5 }} * {{cite book |last=Nei |first=Masatoshi |author-link=Masatoshi Nei |year=1987 |title=Molecular Evolutionary Genetics |publisher=Columbia University Press |isbn=978-0-231-06321-0}} * {{cite journal |last=Nei |first=Masatoshii |author-link=Masatoshi Nei |year=2007 |title=The new mutation theory of phenotypic evolution |journal=PNAS |volume=104 |pages=12235–12242 |doi=10.1073/pnas.0703349104 |pmid=17640887 |issue=30 |pmc=1941456 |bibcode=2007PNAS..10412235N |doi-access=free }} * {{cite journal |doi=10.1093/molbev/msi242 |last=Nei |first=Masatoshi |author-link=Masatoshi Nei |year=2005 |title=Selectionism and Neutralism in Molecular Evolution |journal=Molecular Biology and Evolution |volume=22 |pages=2318–2342 |issue=12 |pmid=16120807 |pmc=1513187}} * {{cite book |last=Nei |first=Masatoshi |author-link=Masatoshi Nei|year=2013 |title=Mutation-Driven Evolution |publisher=Oxford University Press |isbn=978-0-19-966173-2}}</ref><ref>{{ cite journal |first1=David M. |last1=McCandlish |last2=Stoltzfus |first2=Arlin |name-list-style=amp |year=2014 |title=Modeling Evolution Using the Probability of Fixation: History and Implications |journal=Quarterly Review of Biology |volume=89 |issue=3 |pages=225–252 |doi=10.1086/677571 |pmid=25195318 |s2cid=19619966 }}</ref> Nei's book received thoughtful reviews; while Wright<ref name=Wright_2014>{{cite journal |last=Wright |first=S. I. |title=Mutationism 2.0: Viewing Evolution through Mutation's Lens |journal=Evolution |volume=68 |issue=4 |year=2014 |pages=1225–1227 |doi=10.1111/evo.12369|pmid=24673244 |doi-access=free }}</ref> rejected Nei's thinking as mistaken, Brookfield,<ref name=Brookfield_2014>{{cite journal |last=Brookfield |first=J. N. Y. |title=How Evolution Happens |journal=Trends in Ecology & Evolution |date=2014 |volume=29 |issue=4 |page=189 |doi=10.1016/j.tree.2013.12.005 |bibcode=2014TEcoE..29..189B }}</ref> Galtier,<ref name=Galtier_2013>{{cite journal |last=Galtier |first=N. |title=Mutation-Driven Evolution |journal=Syst Biol |date=2013 |volume=63 |pages=113–114 |doi=10.1093/sysbio/syt055|doi-access=free }}</ref> Weiss,<ref name=Weiss_2014>{{ cite journal |last=Weiss |first=Kenneth M. |title=Mutation-Driven Evolution |journal=The American Journal of Human Genetics |volume=93 |issue=6 |pages=999–1000 |doi=10.1016/j.ajhg.2013.11.001 |year=2013|pmc=3852927 }}</ref> Stoltzfus,<ref name=Stoltzfus_on_Nei2014/> and Wagner,<ref name=Wagner_2013/> although not necessarily agreeing with Nei's position, treated it as a relevant alternative view.
=== Contemporary approaches ===
Reviewing the history of macroevolutionary theories, the American evolutionary biologist [[Douglas J. Futuyma]] notes that since 1970, two very different alternatives to Darwinian gradualism have been proposed, both by [[Stephen Jay Gould]]: mutationism, and [[punctuated equilibria]].<ref name=Futuyma/><ref name="Gould1987">{{cite book |last1=Gould |first1=Stephen J. |title=Self-Organizing Systems |chapter=Is a New and General Theory of Evolution Emerging? |author-link=Stephen Jay Gould |year=1987 |pages=113–130 |doi=10.1007/978-1-4613-0883-6_7 |isbn=978-1-4612-8227-3 }}</ref> Gould's macromutation theory gave a nod to his predecessor with an envisaged "Goldschmidt break" between evolution within a species and speciation. His advocacy of Goldschmidt was attacked with "highly unflattering comments"<ref name=Futuyma/> by [[Brian Charlesworth]]<ref>{{cite journal |last=Charlesworth |first=B. |year=1982 |title=Hopeful monsters cannot fly |journal=Paleobiology |volume=8 |issue=4 |pages=469–474 |jstor=2400725 |doi=10.1017/s0094837300007223|s2cid=163847899 }}</ref> and [[Alan Templeton]].<ref>{{cite journal |last=Templeton |first=A. |year=1982 |title=Why read Goldschmidt? |journal=Paleobiology |volume=8 |issue=4 |pages=474–481 |jstor=2400726 |doi=10.1017/s0094837300007235|s2cid=163866832 }}</ref> Futuyma concludes, following other biologists reviewing the field such as K.Sterelny<ref>{{cite journal |last=Sterelny |first=K. |year=2000 |title=Development, evolution, and adaptation |journal=Philosophy of Science |volume=67 |pages=S369–S387 |jstor=188681 |doi=10.1086/392832|s2cid=85008221 }}</ref> and A. Minelli,<ref>Minelli, A. (2010) "Evolutionary developmental biology does not offer a significant challenge to the neo-Darwinian paradigm". In: Ayala, F. J.; Arp, R. (eds) ''Contemporary debates in philosophy of biology''. Wiley, Chichester, pp 213–226</ref> that essentially all the claims of evolution driven by large mutations could be explained within the Darwinian evolutionary synthesis.<ref name=Futuyma>{{cite book |last1=Futuyma |first1=Douglas J. |author-link1=Douglas J. Futuyma |work=Macroevolution |editor1-last=Serrelli |editor1-first=E. |editor2-last=Gontier |editor2-first=N. |title=Can Modern Evolutionary Theory Explain Macroevolution? |date=2015 |publisher=Springer |pages=29–85 |isbn=978-3-319-15044-4 |url=https://www.springer.com/cda/content/document/cda_downloaddocument/9783319150444-c2.pdf?SGWID=0-0-45-1494358-p177219674 |access-date=2017-09-05 |archive-date=2020-02-23 |archive-url=https://web.archive.org/web/20200223084543/https://www.springer.com/cda/content/document/cda_downloaddocument/9783319150444-c2.pdf?SGWID=0-0-45-1494358-p177219674 }}</ref> [[James A. Shapiro]]'s claim that molecular genetics undermines Darwinism has been described as mutationism and an extreme view by the zoologist Andy Gardner.<ref>{{cite journal |last1=Gardner |first1=Andy |title=Darwinism, not mutationism, explains the design of organisms |journal=Progress in Biophysics and Molecular Biology |date=2012 |volume=111 |issue=2–3 |pages=97–98 |doi=10.1016/j.pbiomolbio.2012.08.012 |pmid=23000353 |s2cid=28316833 |url=https://pdfs.semanticscholar.org/2b70/42923d241a575f08d79dd7f596eca8202c7d.pdf |archive-url=https://web.archive.org/web/20170829121605/https://pdfs.semanticscholar.org/2b70/42923d241a575f08d79dd7f596eca8202c7d.pdf |archive-date=2017-08-29 }}</ref>
Cases of [[mutation bias]] are cited by mutationism advocates of the [[extended evolutionary synthesis]] who have argued that mutation bias is an entirely novel evolutionary principle. This viewpoint has been criticized by Erik Svensson.<ref>{{cite book |chapter-url=https://link.springer.com/chapter/10.1007/978-3-031-22028-9_11 |doi=10.1007/978-3-031-22028-9_11 |chapter=The Structure of Evolutionary Theory: Beyond Neo-Darwinism, Neo-Lamarckism and Biased Historical Narratives About the Modern Synthesis |title=Evolutionary Biology: Contemporary and Historical Reflections Upon Core Theory |series=Evolutionary Biology – New Perspectives on Its Development |date=2023 |last1=Svensson |first1=Erik I. |volume=6 |pages=173–217 |isbn=978-3-031-22027-2 }}</ref> A 2019 review by Svensson and David Berger concluded that "we find little support for mutation bias as an independent force in adaptive evolution, although it can interact with selection under conditions of small population size and when standing genetic variation is limited, entirely consistent with standard evolutionary theory."<ref>{{cite journal |last1=Svensson |first1=Erik I. |last2=Berger |first2=David |title=The Role of Mutation Bias in Adaptive Evolution |journal=Trends in Ecology & Evolution |date=1 May 2019 |volume=34 |issue=5 |pages=422–434 |doi=10.1016/j.tree.2019.01.015|pmid=31003616 |bibcode=2019TEcoE..34..422S |s2cid=125066709 }}</ref> In contrast to Svensson and Berger a 2023 review by Arlin Stoltzfus and colleagues concluded that there is strong empirical evidence and theoretical arguments that mutation bias has predictable effects on genetic changes fixed in adaptation.<ref>{{cite journal|author=Cano AV, Gitschlag BL, Rozhoňová H, Stoltzfus A, McCandlish DM, Payne JL|year=2023|title=Mutation bias and the predictability of evolution|journal=Philos Trans R Soc Lond B Biol Sci|url=|volume=378|issue=1877|article-number=20220055|doi=10.1098/rstb.2022.0055|pmid=37004719|doi-access=free|pmc=10067271 }}</ref>
==Historiography==
Biologists at the start of the 20th century broadly agreed that evolution occurred, but felt that the mechanisms suggested by Darwin, including natural selection, would be ineffective. Large mutations looked likely to drive evolution quickly, and avoided the difficulty which had rightly worried Darwin, namely that blending inheritance would average out any small favourable changes.{{efn|Mendelian inheritance, with discrete alleles, solves Darwin's problem, as blending does not occur.{{sfn|Bowler|1989|p=210}}}}{{sfn|Larson|2004|p=121}} Further, large saltatory mutation, able to create species in a single step, offered a ready explanation of why the fossil record should contain large discontinuities and times of rapid change.{{sfn|Larson|2004|pp=127–129, 157–167}}
These discoveries were often framed by supporters of the mid-20th century [[Modern synthesis (20th century)|modern synthesis]], such as [[Julian Huxley]] and [[Ernst Mayr]], as a controversy between the early geneticists—the "Mendelians"—including Bateson, Johannsen, de Vries, Morgan, and Punnett, who advocated Mendelism and mutation, and were understood as opponents of Darwin's original gradualist view, and the biometricians such as Pearson and Weldon, who opposed Mendelism and were more faithful to Darwin. In this version, little progress was made during the [[eclipse of Darwinism]], and the debate between mutationist geneticists such as de Vries and biometricians such as Pearson ended with the victory of the modern synthesis between about 1918 and 1950.{{sfn|Provine|2001|pp=56–107}}<ref name=Stoltzfus_2006>{{cite journal |last=Stoltzfus |first=Arlin |year=2006 |title= Mutationism and the Dual Causation of Evolutionary Change|journal=Evol Dev |volume=8 |pages=304–317 |doi= 10.1111/j.1525-142X.2006.00101.x |pmid=16686641 |issue=3|s2cid=10469049 |url=https://philpapers.org/rec/STOMAT-4 }}</ref> According to this account, the new [[population genetics]] of the 1940s demonstrated the explanatory power of natural selection, while mutationism, alongside [[Alternatives to Darwinism|other non-Darwinian approaches]] such as [[orthogenesis]] and [[structuralism (biology)|structuralism]], was essentially abandoned.<ref>{{cite book |author-link=Ernst Mayr |last=Mayr |first=Ernst |year=2007 |title=What Makes Biology Unique?: Considerations on the Autonomy of a Scientific Discipline |publisher=Cambridge University Press |isbn=978-0-521-84114-6}}</ref> This view became dominant in the second half of the 20th century, and was accepted by both biologists and historians.{{sfn|Smocovitis|1996|pages=1–65}}
A more recent view, advocated by the historians Arlin Stoltzfus and Kele Cable, is that Bateson, de Vries, Morgan and Punnett had by 1918 formed a synthesis of Mendelism and mutationism. The understanding achieved by these geneticists spanned the action of natural selection on [[allele]]s (alternative forms of a gene), the [[Hardy–Weinberg equilibrium]], the evolution of continuously-varying traits (like height), and the probability that a new mutation will [[Fixation (population genetics)|become fixed]]. In this view, the early geneticists accepted natural selection alongside mutation, but rejected Darwin's non-Mendelian ideas about variation and heredity, and the synthesis began soon after 1900.<ref name=Stoltzfus_2006/><ref name=Stoltzfus>{{cite journal |last1=Stoltzfus |first1=Arlin |last2=Cable |first2=Kele |title=Mendelian-Mutationism: The Forgotten Evolutionary Synthesis |journal=Journal of the History of Biology |date=2014 |volume=47 |issue=4 |pages=501–546 |doi=10.1007/s10739-014-9383-2 |pmid=24811736 |s2cid=23263558 |url=https://link.springer.com/content/pdf/10.1007%2Fs10739-014-9383-2.pdf|doi-access=free }}</ref> The traditional claim that Mendelians rejected the idea of continuous variation outright is simply false; as early as 1902, Bateson and [[Edith Rebecca Saunders|Edith Saunders]] wrote that "If there were even so few as, say, four or five pairs of possible allelomorphs, the various [[homozygous|homo-]] and [[heterozygous|hetero-zygous]] combinations might, on seriation, give so near an approach to a continuous curve, that the purity of the elements would be unsuspected".<ref name="BatesonSaunders1902">{{cite journal |last1=Bateson |first1=William |author1-link=William Bateson |last2=Saunders |first2=E. R. |author2-link=Edith Rebecca Saunders |title=Experimental Studies in the Physiology of Heredity |journal=Royal Society. Reports to the Evolution Committee |date=1902 |url=http://post.queensu.ca/~forsdyke/bateson1.htm#Bateson%20&%20Saunders%20(1902) |access-date=2017-08-23 |archive-date=2020-04-23 |archive-url=https://web.archive.org/web/20200423144636/http://post.queensu.ca/~forsdyke/bateson1.htm#Bateson%20&%20Saunders%20(1902) }}</ref>
Historians have interpreted the history of mutationism in different ways.{{sfn|Provine|2001|pp=56–107}}<ref name=Stoltzfus_Cable_2014>{{cite journal |last1=Stoltzfus |first1=A. |last2=Cable |first2=K. |year=2014 |title=Mendelian-Mutationism: The Forgotten Evolutionary Synthesis |journal=Journal of the History of Biology |volume=47 |issue=4 |pages=501–546 |doi=10.1007/s10739-014-9383-2|pmid=24811736 |doi-access=free }}</ref><ref name=Roll-Hansen_1989/>{{sfn|Gayon|1988|pages=289 and passim}} The classical view is that mutationism, opposed to Darwin's gradualism, was an obvious error; the decades-long delay in synthesizing genetics and Darwinism is an "inexplicable embarrassment";<ref name=Hull_1985>{{ cite book |first=D. L. |last=Hull |year=1985 |chapter=Darwinism as an historical entity: A historiographic proposal |editor-first=D. |editor-last=Kohn |title=The Darwinian Heritage |chapter-url=https://archive.org/details/darwinianheritag00davi |chapter-url-access=registration |publisher=Princeton University Press |isbn=978-0-691-63365-7 |pages=[https://archive.org/details/darwinianheritag00davi/page/773 773–812]}}</ref> genetics led logically to the modern synthesis and mutationism was one of several anti-Darwinian "blind alleys" separate from the main line leading from Darwin to the present.{{sfn|Bowler|1989|pp=276–281}} A revisionist view is that mutationists accepted both mutation and selection, with broadly the same roles they have today, and early on accepted and indeed offered a correct explanation for continuous variation based on multiple genes, paving the way for gradual evolution. At the time of the Darwin centennial in Cambridge in 1909, mutationism and [[Lamarckism]] were contrasted with natural selection as [[Alternatives to Darwinism|competing ideas]]; 50 years later, at the 1959 University of Chicago centennial of the publication of ''[[On the Origin of Species]]'', mutationism was no longer seriously considered.<ref name=Tax60>{{ cite book |editor1=Tax, S. |editor2=Callender, C. |year=1960 |title=Evolution After Darwin: The University of Chicago Centennial |url=https://archive.org/details/evolutionafterd003taxs |url-access=registration |publisher=University of Chicago Press, Chicago}}</ref>{{sfn|Smocovitis|1996|pages=1–65}}
==See also== * [[History of evolutionary thought]] * [[Rapid modes of evolution]]
==Notes== {{notelist}}
==References== {{Reflist|30em}}
==Sources== * {{cite journal |last=Allen |first=Garland E. |title=Thomas Hunt Morgan and the problem of natural selection |journal=Journal of the History of Biology |date=1968 |volume=1 |issue=1 |pages=113–139 |doi=10.1007/BF00149778 |s2cid=84932356}} * Bateman, Richard M.; DiMichele, William A. (2002). ''Generating and Filtering Major Phenotypic Novelties, NeoGoldschmidtian Saltation Revisited''. In Cronk, Q. C. B.; Bateman R. M.; Hawkins J. A. eds. ''Developmental Genetics and Plant Evolution''. London: Taylor and Francis. pp. 109–159. <!--* {{cite book |last=Bowler |first=Peter J. |author-link=Peter J. Bowler |title=The Eclipse of Darwinism: anti-Darwinian evolutionary theories in the decades around 1900 |publisher=Johns Hopkins University Press |year=1983 |isbn=978-0-8018-4391-4 }}--> * {{cite book |last=Bowler |first=Peter J. |author-link=Peter J. Bowler |title=Evolution:The History of an Idea |publisher=University of California Press |year=2003 |orig-date=1983 |edition=New |isbn=978-0-520-23693-6 |url-access=registration |url=https://archive.org/details/evolutionhistory0000bowl_n7y8 }} * {{cite book |last=Bowler |first=Peter J. |author-link=Peter J. Bowler |title=Evolution:The History of an Idea |publisher=University of California Press |year=1989 |orig-date=1983 |edition=Revised |isbn=978-0-520-06386-0 |url-access=registration |url=https://archive.org/details/evolutionhistory0000bowl }} * [[William Bateson|Bateson, William]]. (1894). [https://archive.org/stream/materialsforstud00bate#page/n5/mode/2up ''Materials for the Study of Variation: Treated with Especial Regard to Discontinuity in the Origin of Species'']. Macmillan. * {{cite book |last=Endersby |first=Jim |title=A Guinea Pig's History of Biology |publisher=Harvard University Press|year=2007 |isbn=978-0-674-02713-8 }} * {{cite book |last=Gayon |first=J. |title=Darwinism's Struggle for Survival: Heredity and the Hypothesis of Natural Selection |year=1988 |publisher=Cambridge University Press }} * {{cite book |last=Larson |first=Edward J. |author-link=Edward J. Larson |title=Evolution: The Remarkable History of a Scientific Theory |url=https://books.google.com/books?id=xzLRvxlJhzkC |year=2004 |publisher=Random House |isbn=978-1-58836-538-5 }} * {{cite book |last=Provine |first=W. B. |year=2001 |title=The Origins of Theoretical Population Genetics, with a new afterword |publisher=University of Chicago Press, Chicago }} * {{cite book |last=Ruse |first=Michael |author-link=Michael Ruse |date=1996 |title=Monad to Man: the Concept of Progress in Evolutionary Biology |url=https://archive.org/details/monadtomanconcep0000ruse |url-access=registration |publisher=Harvard University Press |isbn=978-0-674-03248-4 }} * {{cite book |last=Smocovitis |first=Vassiliki Betty |year=1996 |title=Unifying Biology: The Evolutionary Synthesis and Evolutionary Biology |journal=Journal of the History of Biology |volume=25 |issue=1 |pages=1–65 |location=Princeton, New Jersey |publisher=Princeton University Press |doi=10.1007/bf01947504 |pmid=11623198 |isbn=978-0-691-03343-3 |s2cid=189833728 |lccn=96005605 |oclc=34411399 }}
{{Evolution}}
[[Category:Mutationism|Mutationism]] [[Category:Biology theories]] [[Category:Extended evolutionary synthesis]] [[Category:Evolutionary biology]] [[Category:Molecular evolution]] [[Category:Mutation]]