Talk:Mutationism

message: I have updated the claim by Singer and Ames that a high G+C content could be selectively
advantageous with a new reference to Palmeira et al. (2006) Jean R. Lobry 20:05, 3 January 2007 (UTC)
thread_title:  UV and GC content 

message: I can't find an answer to this question, and thought I would post it here: How do chromosome numbers change?  Say a population of a given species, all of which share the same chromosome number, is isolated from the main population.  Time goes by.  Now the chromosome numbers are different in the two populations.  Does that happen?  If so, how?  By what mechanisms?  --Serge 23:48, 6 December 2005 (UTC)
thread_title:  Question: chromosome change? 

message: I removed the following sentence: 
It was also demonstrated that levels of mutation necessary to cause significant evolution were not present in the environment and would cause sterility; e.g., in fruit flies. 
This sentence does not make sense and does not make reference to any recognizable 
facts.  It refers to "levels of mutation . . . present in the environment", but mutation 
is not present in the environment, it is a process within organisms.  By referring 
to sterility and fruit flies, the statement makes it sound like it is based on 
some specific experimental result.  If so, what is the result?  What is the 
reference?  
:Yes. You irradiate fruit flies to produce mutations.  It's quicker than waiting for them to happen naturally.  You give them too much juice and they can't get it on.  As for a reference, it's really at the level of common knowledge, but you might try to find something by Thomas Hunt Morgan, probably early 1930s. — Dunc|☺ 17:30, 19 May 2006 (UTC)
replies: text: I agree with Dabs (who should sign his name using ~~~~). This part is ambiguous. It shouldn't be removed, but at least clearly explained. -PhDP 02:48, 20 May 2006 (UTC)
replies: text:  It makes perfect sense.  The frequency of mutations required to cause significant evolution is far more than an organism can sustain, as demonstrated by the fact that if you artificially increase the frequency of mutations to that level, you get sterility.  Now improve the wording, find a reference if you feel you need to, but don't remove it because you can't understand it. — Dunc|☺ 10:17, 20 May 2006 (UTC)
replies: text:  To make sense here, this argument would have to relate to mutationism, i.e., the view of De Vries and (in a later form) Bateson, Punnett, Morgan, etc.  The argument seems to have three parts: 1) there is some level of mutation L "required to cause significant evolution"; 2) when the level of mutation is increased beyond L, sterility results; and 3) this somehow contradicts mutationism without contradicting other theories that erly on mutation.  You have only addressed #2 (incompletely).  How have you determined the level of mutation "required to cause significant evolution"?  How does it relate to mutationism?  De Vries found *actual cases* in Oenothera in which distinctive true-breeding forms arise in a single step that he called "mutation".  De Vries's theory of evolution invoked this process and subsequent selection (i.e., De Vries was a radical species-selectionist: he doubted that within-species variation and selection could account for adaptation and diversity).  Doesn't that vitiate the argument that the mutation rate is too low in nature?  Later mutationists, such as Punnett and Morgan, did not accept De Vries's view, and invoked "gene mutations" as opposed to the kinds of chromosomal rearrangements common in Oenothera.  However, in neither case is there a requirement for a high rate of parallel mutations to cause a mass conversion of the population from one form to another.  This argument does not belong here, but perhaps in the entry on Ernst Mayr or Straw Man.  --Dabs 12:48, 22 May 2006 (UTC)
thread_title:  Removal of claimed "nonsense" 

message: AFAIK saltationism is opposed to gradualism (not "phyletic gradualism", which opposes punctuated equilibrium, both almost unrelated). Meaning that it allows for or affirms a greater role for mutations causing a more drastic phenotypic difference, as opposed evolution being restricted to gradual variation, the sort of mundane additive variation that accounts for the bulk of ordinary variation in living populations. For concrete but hypothetical examples, in the ancestors of whales, mutations that abort completely or much more dramatically the size of the hind legs/"fins", rather than the ordinary minute variation in size; for eyeless animals, mutations that simply abort the development of the eye (or even one eye, as may be the case with the Mexican tetra), versus genes for progressively more minute but normal eyes, over generations, until they finally reach phenotypic nonexistence. "Freaks", as opposed to "normals". And that is regardless of the "size" or whatever genetic aspect of the mutation at the DNA level -- DNA wasn't even known then. And even "mutationism" doesn't refer to "size" of mutations at the genetic level, but is rather about mutation as a "driving force" alongside selection, rather than just providing the "raw material". That is, if some mutations are recurring enough, they will add to the genetic frequencies of such recurring alleles, at least against neutral variation, and possibly even against some negative selection (maladaptive alleles aren't always completely eliminated, and can even be maintained or increase in frequency if they provide some compensatory advantage, such as sickle cell anemia versus malaria), with the end result possibly coupling alleles of other genes to cope with a recurring maladaptive variation. I can't provide references for such definitions right now, but if I'm not mistaken, this series of articles at the Sandwalk blog will corroborate at least the mutationism "versus" selectionism aspect, mutation as a driver of genetic frequencies.  — Preceding unsigned comment added by 189.18.92.181 (talk) 19:56, 25 June 2017 (UTC)
replies: text:  Hm, this (and the previous thread, which makes a similar point) will need careful attention. I see from the Sandwalk blog by Stoltzfus that "Apropos, the following quotation from Ernst Mayr never fails to make me [Arlin Stoltzfus] laugh: 'The genetic work of the last four decades has refuted mutationism (saltationism) so thoroughly that it is not necessary to repeat once more all the genetic evidence against it.' (Mayr, 1960)". This shows that I was following a tradition which at least included Mayr in equating mutationism and saltationism, so I did have a RS available if I'd wanted it. Obviously, genetics didn't exist before 1900, though the idea of a sudden freak was available long before that, and knowledge of DNA and its coding wasn't available until 1953, long after the early mutationists. Mayr, I now appreciate, had an axe to grind, and Stoltzfus is I think right in arguing that Mayr (and Huxley, and others) was pushing a story that favoured his side (politics with a small p). There is clearly some kind of continuity between saltationism and mutationism, but the story is richer than Mayr would have it. I'll read some more and hope to improve the article stepwise rather than, um, in sudden jumps. I agree with Dabs that one change I made, namely to treat the topic evenly and historically with names, actions, dates and citations is beneficial, not least because it acts to counter what Stoltzfus calls "myths", and what I'd call political story-pushing, or selling a party line. This will take time so please bear with me. All help appreciated. Chiswick Chap (talk) 07:29, 22 August 2017 (UTC)
replies: text: Erm, mutationism is definitely not saltationism. There's kind-of a relationship, insofar as saltationism relies on extreme mutants (Goldschmidt's "hopeful monsters"), but mutationism is not primarily concerned with macromutations. So, to my mind, the opening sentence is entirely off-base. My reading is that mutationism suggests that, instead of particular mutations being favoured by differential organism survival and prospering (i.e. selection), what actually happens is that mutations become dominant in a population via their somehow elevated (and there's the rub) frequency of occurrence. And this does not have anything to do with saltationism. Admittedly, it's difficult to think of mutationism as anything other than absurd given that different organisms will inevitably have different survival and reproduction rates (i.e. selection). Anyway, I feel a rethink is needed here. --PLUMBAGO 13:46, 22 August 2017 (UTC)
replies: text:  That's already agreed. I have reverted the redirect of Saltationism so the articles are again separate, and removed purely saltationist material from here. However, macromutationism (enormous sudden jumps) is certainly saltationist, and much early saltationist thinking anticipates mutationism, that mutations can drive evolution. So overlap between the two articles is necessary. When mutationism means that mutations create variation, drive evolution, or simply make it possible, on the other hand, that's not at all saltationist. Mutationism was certainly not absurd in 1909, and the experimental work of the early Mendelian / Mutationist geneticists was valuable. Chiswick Chap (talk) 13:56, 22 August 2017 (UTC)
replies: text: Good. I can see it's already changed quite a bit since I wrote before (of which, the opening sentence is completely different, so my statement above on this might have been confusing). I would agree, incidentally, about the less-absurdness of mutationism at the start of the 20th century - I was thinking of now, when it's actually difficult to articulate mutationism without it sounding rather odd. Cheers, and thanks for the good (and clearly ongoing) work on the article. --PLUMBAGO 15:41, 22 August 2017 (UTC)
thread_title:  Possibly incorrect conflation of concepts, saltationism and mutationism