Talk:Evolution/Archive 39

message: I propose that there be a "Robustness" section before even genetic drift as a mechanism of evolution.  "Robustness" subsumes the concepts of redundancy and overlapping function, homeostasis, developmental homeostasis, canalization and niche reduction.  Robustness enables evolvability.
*"All living things are remarkably complex, yet their DNA is unstable, undergoing countless random mutations over generations. Despite this instability, most animals do not grow two heads or die, plants continue to thrive, and bacteria continue to divide. Robustness and Evolvability in Living Systems tackles this perplexing paradox. The book explores why genetic changes do not cause organisms to fail catastrophically and how evolution shapes organisms' robustness."
*"That physiological homeostasis is essentially the fundamental adaptation was recognized even before the term was coined, for, as Claude Bernard (quoted from Haldane,1932) stated three-quarters of a century ago, 'all the vital mechan­sms, varied as they are, have only one object, that of preserving constant the conditions of life in the internal environment'."
*"Homeostatic devices that stabilize an individual's reproductive performance have high selective value; the population benefits from having a heterogeneous genetic composition even beneath an apparently uniform phenotype. Thus Lerner emphasized the very great importance in evolution of "buffered and balanced genotypes, integrated genepools, and coadaptation.""
*"In a rapidly fluctuating environment, organisms evolve the flexibility to cope with variation within an individual lifetime; in moderately variable environments, populations evolve the ability to evolve rapidly; and in fairly constant environments, populations evolve robustness against the adverse effects of mutation." "When environmental fluctuations are rare, populations may experience extended epochs of directional selection and thus have sufficient time to achieve genetic robustness for any given state. Immediately following an environmental shift, however, such populations may pass through transitional periods of within-individual or between-generation plasticity before completely losing the previously favored phenotype in favor of a currently favored phenotype. This evolutionary transformation—from a trait that is acquired through phenotypic plasticity to a genetically determined version of the same trait—is known as the Baldwin Effect"
*"Many amphibian and reptile taxa experience dramatic shifts in their environment through development, essentially having to function in different niches. For instance, the komodo dragon (Varanus komodoensis) begins life as an arboreal predator of small insects, progressively moves onto larger insects, small vertebrates and eggs, then larger vertebrates and eventually fills a terrestrial large predator/scavenger niche (Auffenberg, 1981). Mutations providing a potential fitness advantage at any point along this continuum may be deleterious somewhere else during growth. This effect is less in mammals and birds because they typically feed their young until they can occupy the adult niche." "Compared with other vertebrates, mammals and birds are also notable for an increased emphasis on homeostasis, particularly endothermy (Ruben, 1995), so stabilising internal biochemical and physiological conditions. Both effects, reducing the range of niches during development and stabilising internal conditions, should enhance morphological evolvability.  Indeed, while mammals and birds have diversified into widely different niches and morphologies from their ancestors that shared the planet with dinosaurs 65 million years ago, amphibians, turtles, lepidosaurs (snakes and lizards) and crocodilians typically have not (Benton, 1993). " 
*"A mechanism for `evolvability'? We have provided what is, to our knowledge, the ®rst evidence for an explicit molecular mechanism that assists the process of evolutionary change in response to the environment. We suggest that in nature, transient decreases in Hsp90 levels resulting from its titration by stress-damaged proteins could uncover morphological variants for selection to act upon....Evolutionary models must encompass a dichotomy of stasis and change. Evolution exploits genetic differences between individuals in order to remodel developmental programs, yet development is generally robust to individual genetic differences and environmental perturbations. Theoretical models describe how developmental homeostasis is developed and why it is maintained, as well as how it could be disrupted so that evolutionary change can occur"
The robustness mechanism that I think I had not appreciated before was niche reduction.  The most exemplary of this is parental care.  Think of all the mutations which are developmentally deleterious, yet can be tolerated because of parental care, and are advantageous to the adult.  Think of all the mutations that made the human baby this slow, defenseless, sniveling, noisey predator attracting, relatively instinctless, large brained, empty headed little beast.  Yet parental care allows that helpless large brain to develop into the most robust adaptation that evolution has yet devised.  This was done through niche reduction.  Mutations don't have to be developmentally stable in any niche other than that formed by the womb and parental care.
Robustness to mutation, and to the breaking of seemingly irreducable complexity appear to be the concepts that the ID adherants aren't familiar with, and which answers most of the issues they raise. --Africangenesis 12:09, 15 May 2007 (UTC)
replies: text: Interesting sources, this might fit best as a paragraph in the mutation section. Robustness does not change the allele frequency of populations, so it can't be classed as a mechanism of evolution. While "evolvability" would fit well with the discussion of the variation of bacterial mutation rates in response to stress. TimVickers 16:59, 15 May 2007 (UTC)
replies: text: I am not sure of the significance of this distinction, but I think it is clear that robustness, while technically not creating new alleles, is the key mechanism which allows their numbers to increase, e.g., "the population benefits from having a heterogeneous genetic composition even beneath an apparently uniform phenotype"  Inherent in a lot of ID rhetoric is this idea that the well adapted organism is somehow perfect, so that any mutation must somehow be a deleterious deviation from that perfection.  Robustness, not only protects fitness while harbouring a storehouse of alleles, but also protects evolution from ID perfectionist arguments.  The enhanced evolvability enabled by robustness, may be evolution's most robust achievement.  To paraphrase Jurrasic Park, "life has found a way".--Africangenesis 17:21, 16 May 2007 (UTC)

text: Well, I'm just trying to think about where to put this in the article. I think it would go best in "Mutation" as it impacts the effects of mutations. It can't go in the "Evolutionary mechanisms" section as this only deals with processes that change allele frequencies. I suppose robustness and evolveability could be seen as outcomes of evolution, but we have many examples of adaptations already. TimVickers 17:40, 16 May 2007 (UTC)
replies: text: I'm thinking on it too.  One thought I've had is the introduction, which currently is very sterile.  Life and this characteristic robustness it has, is not even mentioned.  Since this article has been noted as specific to the biological form, I think it would be entirely appropriate to mention life.--Africangenesis 18:05, 16 May 2007 (UTC)
thread_title:  Robustness 

message: I just reverted Adam's deletion of "theory of."  Look, there is always a close conntextion between theory and fact.  Moreover, we all agree evolution is sometimes clearly a fact and sometimes clearly a theory.  Adam thinks it is not clear what a theory is.  Well, let's make it clear.  And also let's be consistent.  When we are talking about evolution as a fact (finches, hawthorne flies) let's just use the word "evolution."  But it would only muddy the waters if we always and only used the word evolution alone.  When we are talking about models of evolution and mechanisms of evolution we should be clear we are talking about the (or a ) theory of evolution.  Darwin's arguments about evolution by natural selection is a theory, it really is.  And it is a great theory!  But whether you think it is a great theory or not, let's not hide that fact that it is a theory. Slrubenstein   |  Talk 16:03, 15 May 2007 (UTC)
replies: text: The only accurate rephrasing for the sentence would be something like "put forth a model explaining evolution", but that would be less intelligible, simple, and accessible to readers, plus it would introduce confusing inconsistency: why is "theory" used everywhere else in the article, but not here? The implication is that "evolution" doesn't mean "evolutionary theory" here, when in fact it is supposed to. This is similar to the problem that arose when we tried to use "characteristic" in the first few sentences of the article, but "trait" for the rest of the page: it made the article more complicated by confusing readers about why we were jumping back and forth between terminology. -Silence 16:29, 15 May 2007 (UTC)
replies: text: Is it possible our defensiveness against using "Theory of Evolution" may be that certain individuals have used that descriptive as a pejorative against the reality of Evolution?  The fact is that outside of our friends on the Creationist side, we would use Theory of Evolution to describe it.  Orangemarlin 01:50, 16 May 2007 (UTC)
replies: text: I fully agree. Of course, we must take into account the reality of the situation: we're writing for laypeople, not scientists, and consequently we should, realistically, expect a lot of our readers to not know the scientific meaning of "theory". However, that doesn't mean we shouldn't use the word "theory"; it means we should be careful in how we use the word so as to make its meaning as clear and consistent as possible, and that we should link to its article so people can read up about it and clear up their misconceptions. -Silence 02:06, 16 May 2007 (UTC)
replies: text: I recall a few months ago we had to stand firm against renaming this article to "Theory of Evolution."  As long as certain individuals have hijacked the word "theory" so that in laymen terms it appears that there's little science or thought behind this theory, we need to reaffirm that Evolution, as theories go, is about as close to a fact as you can get without having a time lapse camera that filmed the earth for 2 billion years give or take a billion.  Orangemarlin 23:13, 16 May 2007 (UTC)
thread_title:  My revert 

message: I've addeds an image to the Variation section. I think it's useful, you may disagree. Adam Cuerden talk 00:51, 17 May 2007 (UTC)
replies: text: I do disagree. This is a science article. -Silence 01:01, 17 May 2007 (UTC)
replies: text: Aye, but I couldn't find a good photographic depiction of variation at the species level, and that sketch seemed to illustrate it well. Adam Cuerden talk 04:01, 17 May 2007 (UTC)
replies: text: If you can't find a good photographic depiction, then why add an image at all? The drawings are ridiculous, practically caricatures, and of no scientific value: they don't help people understand anything about evolution, beyond the (obvious) basic fact that not everyone looks exactly the same! Besides, ideally we should choose a non-human species, because everyone already knows that all people look different; what they may not realize is that all non-human species demonstrate (sometimes subtle) phenotypic variation as well. But I think the best image would be something that helps hammer home one of the many very difficult concepts that we discuss in "variation": we only have a limited amount of space to insert images, and every single one of them should help optimize readers' understanding of evolution. A diagram comparing phenotype and genotype, or clearly and non-technically showing how allele frequency varies, for example, would be more valuable than some silly picture showing something as trivial as the fact that not all humans have the same faces! -Silence 04:36, 17 May 2007 (UTC)

text: I agree with silence here, the graphic is an awful representation of variation. David D. (Talk) 17:50, 17 May 2007 (UTC)
thread_title:  Variation 

message: This isn't exactly a huge dispute, but it's about a description of natural selection, so if anyone wanted to weigh in at Talk:Intelligent_design#Reversion, I'd appreciate it. I fear my views on it are abundantly clear over there, but I am willing to shut up if enough people disagree. =) Adam Cuerden talk 00:54, 17 May 2007 (UTC)
thread_title:  Intelligent design mini-dispute 

message: I haven't looked at the article in a while and I came back and it looks great! Congrats to all you who helped fix it up!Meson man 23:29, 17 May 2007 (UTC)
replies: text: We're hoping to get it through the FA process soon, but I've been saying "any day now" for a few weeks! TimVickers 23:59, 17 May 2007 (UTC)

text: Any help is appreciated. Any contributions to the article - copy editing, clarifying, addressing points in the peer-review - are useful. The most valuable editors are those who are positive contributors and actually add something to the text. TimVickers 04:02, 18 May 2007 (UTC)
thread_title:  CONGRATS 

message: I changed the thumbnail in the illustration for natural selection by placing the word dark instead of light. Meson man 04:13, 18 May 2007 (UTC)
thread_title:  minor edit 

message: As this page has reached the staggering size of 285kb, I've changed the archive bot setting to 3 days and compacted some of the older and inactive discussions. Yesterday we had 22 edits on the article and 133 edits on the talk page. TimVickers 15:35, 18 May 2007 (UTC)
replies: text: Where did you set that to 3 days, I'd like to set it back.--Africangenesis 16:58, 18 May 2007 (UTC)
replies: text: In the past we have also manually archived certain sections of the talkpage on an as-needed basis. Any section which is no longer active, or which is actively counter-productive (ie, Creationist nonsense) can be considered for premature manual archiving. Doc  Tropics 17:22, 18 May 2007 (UTC)
replies: text: I've changed it to 9 days. 285kb is not large, if a reader thinks it is, they must be avoiding any pages with pictures also, unlikely on today's internet.  I've got context up there that that I want it to be easy for others to refer to during future work, and I don't want to have to pad it to keep it around.  The compaction also is a problem as it interferes with word searches on the page, without any benefit in reducing the size of the load.--Africangenesis 17:26, 18 May 2007 (UTC)

text: Should I do a straw poll on if we need the compaction? ;) TimVickers 17:28, 18 May 2007 (UTC)
thread_title:  Compaction