Talk:Evolution/Archive 57

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Gene flow suggested text

Here is a start, originally based on breaking up the existing text. It will eventually matter whether variation or mechanisms comes first. Meantime, for variation,

Gene flow is the exchange of genes between populations, and between species.[1] It can therefore be a source of variation that is new to a population or to a species.
Gene flow can be caused by the movement of individuals between separate populations of organisms, as might be caused by caused by the movement of mice between inland and coastal populations, or the movement of pollen between heavy metal tolerant and heavy metal sensitive populations of grasses.
Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer. Horizontal gene transfer is the transfer of genetic material from one organism to another organism that is not its offspring; this is most common among bacteria.[2] In medicine, this contributes to the spread of antibiotic resistance, as when one bacteria acquires resistance genes it can rapidly transfer them to other species.[3] Horizontal transfer of genes from bacteria to eukaryotes such as the yeast Saccharomyces cerevisiae and the adzuki bean beetle Callosobruchus chinensis has occurred.[4][5] An example of larger-scale transfers are the eukaryotic bdelloid rotifers, which have received a range of genes from bacteria, fungi, and plants.[6] Viruses can also carry DNA between organisms, allowing transfer of genes even across biological domains.[7]
Large-scale gene transfer has also occurred between the ancestors of eukaryotic cells and bacteria, during the acquisition of chloroplasts and mitochondria. It is possible that eukaryotes themselves originated from horizontal gene transfers between bacteria and archaea [8]

For mechanisms,

The presence or absence of gene flow fundamentally changes the course of evolution. Because of the complexity of organisms, any two completely isolated populations will eventually evolve genetic incompatibilities through neutral processes, as in the Bateson-Dobzhansky-Muller model, even if both populations remain essentially identical in terms of their adaptation to the environment.
If genetic differentiation between populations develops, gene flow between populations can introduce traits or alleles which are disadvantageous in the local population, and this may lead to organism within these populations to evolve mechanisms that prevent mating with genetically distant populations, eventually resulting in the creation of new species. Thus, exchange of genetic information between individuals is fundamentally important for creating the biological concept of Species.
During the development of the modern synthesis, Sewall Wright's developed his shifting balance theory that gene flow between partially isolated populations was an important aspect of adaptive evolution.[9] However, recently there has been substantial critisism of the importance of the shifting balance theory[10].

Let's take edits from here. BTW, after some investigation (I wanted to reprint in a Trends article), there appears to be no copyright applying to Wright's 1932 paper, so if anyone wants to scan and upload either for this or many other evolutionary pages, they should feel free. Joannamasel (talk) 16:25, 2 June 2011 (UTC)

Consolidated edits. Matthew Ackerman (talk) 13:28, 3 June 2011 (UTC)
Are these edits good to go? If so, I will insert them. mezzaninelounge (talk) 15:07, 3 June 2011 (UTC)
As far as I am concerned, yes. Refs would be good for the mouse and grass examples, but they can be inserted after this is on the main page. Joannamasel (talk) 15:42, 3 June 2011 (UTC)

OK, but before I do that, I think we should removed the population genetics text from the variation section, reedit it as follows, and reinsert it as part of first paragraph of the mechanisms section.

From a Neo-Darwinian perspective, evolution is a generation-to-generation change in the frequencies of alleles within a population that shares a common gene pool.[11] According to the Hardy-Weinberg principle, the frequencies of alleles in a gene pool within a sufficiently large population will remain constant if the only forces acting on that population are the random reshuffling of alleles during the formation of the sperm or egg and the random combination of the alleles in these sex cells during fertilisation.[12] Evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms, For example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, gene flow and mutation.

Thoughts? mezzaninelounge (talk) 16:43, 3 June 2011 (UTC)

I'd like to edit the gene flow section a little more, particularly I feel that examples of HGT could be cleaned up, and I'll grab those references. Matthew Ackerman (talk) 20:18, 3 June 2011 (UTC)

Population genetics suggested text

I'm not too keen on gene pools. While they appear in introductory textbooks, their usefulness is disputed by some, like Provine and Mayr, because they neglect both linkage and population structure. Generality is lost, and on the flip side, I don't see what is gained by referring to them. And are you positive that is the right ref for that first sentence? Ironic that it was part of the old text, given the recent discussion on mutation as mechanism. I put the Ewens monograph in instead, cited twice so it should get a name so they link together. Also, I support H-W under variation for reasons I have discussed earlier, but I don't think it adds much to mechanisms of evolution as a reason for absence-of-evolution. I would cut the text down to the following even shorter lead-within-mechanisms.

From a Neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms.[13] For example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, gene flow and mutation.

But then I would retain a brief H-W section under mechanisms, as below, taken from the current article.

Natural selection will only cause evolution if there is enough genetic variation in a population. Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible. The Hardy-Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance. According to this principle, the frequencies of alleles (variations in a gene) in a sufficiently large population will remain constant if the only forces acting on that population are the random reshuffling of alleles during the formation of the sperm or egg, and the random combination of the alleles in these sex cells during fertilisation.[14]

More edit before insertion? Joannamasel (talk) 17:14, 3 June 2011 (UTC)

Joanna, if you would like to edit more, feel free. I didn't tinker with the references, so whatever you saw was in the original text. I just shortened the entire description. I just think that this section needs to be removed as its own standalone subsection within the variation section. We can insert it as part of the first paragraph in the variation section. The reason why I would prefer that it goes into the mechanism section is that H-W has been used as a null hypothesis to see if evolution has occurred. The violation of the assumptions of H-W are essentially the listed mechanisms in the mechanism section. I think readers might find that aspect/utility of H-W most interesting/informative. But I'm not opposed to other suggestions as well. I just don't like seeing it as a subsection of variation only because such an organization might mislead or confuse naive readers to think that population genetics is a major source of variation, which it is not. mezzaninelounge (talk) 17:25, 3 June 2011 (UTC)
BTW, I am not sure if I understood you correctly, are you suggesting we replaced the entire first paragraph under mechanisms with your suggested edits from above or do we put that before the first paragraph? If it is the latter, then we would also have to reedit the second paragraph so that it transitions from the first.
Before the current first paragraph, yes transition needs an edit.Joannamasel (talk) 17:42, 3 June 2011 (UTC)
I'm done editing. In research, H-W is not used as a null hypothesis to see if evolution has occurred, although sometimes undergraduate courses can give that false impression. The problem is that it takes only a single generation of random mating to reach H-W genotype ratios. H-W is used in research as a null hypothesis to detect assortative mating / population structure. Which makes the use of H-W as null hypothesis a little peripheral in a general article on evolution. Anyway, I agree with no longer using population genetics as a subheading, and using it in the intro part of variation instead. Joannamasel (talk) 17:39, 3 June 2011 (UTC)
Is that right (H-W not used as null hypo in research)? OK, if we put it in as the first paragraph of the variation section, then this is what it would look like:
From a Neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms.[15] For example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, gene flow and mutation. Natural selection will only cause evolution if there is enough genetic variation in a population. Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible. The Hardy-Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance. According to this principle, the frequencies of alleles (variations in a gene) in a sufficiently large population will remain constant if the only forces acting on that population are the random reshuffling of alleles during the formation of the sperm or egg, and the random combination of the alleles in these sex cells during fertilisation.[16]
An individual organism's phenotype results from both its genotype and the influence from the environment it has lived in. A substantial part of the variation in phenotypes in a population is caused by the differences between their genotypes.[17] The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will fluctuate, becoming more or less prevalent relative to other forms of that gene. Evolutionary forces act by driving these changes in allele frequency in one direction or another. Variation disappears when a new allele reaches the point of fixation — when it either disappears from the population or replaces the ancestral allele entirely.[18]
Variation comes from mutations in genetic material, migration between populations (gene flow), and the reshuffling of genes through sexual reproduction. Variation also comes from exchanges of genes between different species; for example, through horizontal gene transfer in bacteria, and hybridisation in plants.[19] Despite the constant introduction of variation through these processes, most of the genome of a species is identical in all individuals of that species.[20] However, even relatively small changes in genotype can lead to dramatic changes in phenotype: for example, chimpanzees and humans differ in only about 5% of their genomes.[21]
Is this what you had in mind? mezzaninelounge (talk) 18:11, 3 June 2011 (UTC)
I would have the first 3 sentences as intro to mechanisms, not intro to variation. I would reorder 2 paragraphs in variation. So for mechanisms we have
From a Neo-Darwinian perspective, evolution occurs when there are changes in the frequencies of alleles within a population of interbreeding organisms.[22] For example, the allele for black colour in a population of moths becoming more common. Mechanisms that can lead to changes in allele frequencies include natural selection, genetic drift, gene flow and mutation.
And for variation, where I have also removed a bit of redundancy and mechanism material to shorten it, and changed "changes" to "differences" at the end, how about
An individual organism's phenotype results from both its genotype and the influence from the environment it has lived in. A substantial part of the variation in phenotypes in a population is caused by the differences between their genotypes.[17] The modern evolutionary synthesis defines evolution as the change over time in this genetic variation. The frequency of one particular allele will become more or less prevalent relative to other forms of that gene. Variation disappears when a new allele reaches the point of fixation — when it either disappears from the population or replaces the ancestral allele entirely.[18]
Natural selection will only cause evolution if there is enough genetic variation in a population. Before the discovery of Mendelian genetics, one common hypothesis was blending inheritance. But with blending inheritance, genetic variance would be rapidly lost, making evolution by natural selection implausible. The Hardy-Weinberg principle provides the solution to how variation is maintained in a population with Mendelian inheritance. According to this principle, the frequencies of alleles (variations in a gene) in a sufficiently large population will remain constant if the only forces acting on that population are the random reshuffling of alleles during the formation of the sperm or egg, and the random combination of the alleles in these sex cells during fertilisation.[23]
Variation comes from mutations in genetic material, migration between populations (gene flow), and the reshuffling of genes through sexual reproduction. Variation also comes from exchanges of genes between different species; for example, through horizontal gene transfer in bacteria, and hybridisation in plants.[24] Despite the constant introduction of variation through these processes, most of the genome of a species is identical in all individuals of that species.[25] However, even relatively small differences in genotype can lead to dramatic differences in phenotype: for example, chimpanzees and humans differ in only about 5% of their genomes.[26]

Joannamasel (talk) 18:38, 3 June 2011 (UTC)

Those look good to me. If nothing else, I think we can now insert the gene flow texts into the gene flow sections as well as modify the lead paragraphs under the mechanism and variation sections. After that, we should finish off with the mutation bits and then move on to see how this entire article can be updated. mezzaninelounge (talk) 18:46, 3 June 2011 (UTC)

Let's do it

Seems a good critical mass of editors with good proposals has reached some grounds of agreement. Why not address these issues. Graft and numerous other editors that is too long to mention have written older versions and their input is valuable. But we need to make the changes and all recruit good editors we respect who are naive about evolution. What good is a great article that novices can't understand. I'm more of cell biologist and anatomist, and study evolution because you can't escape it's influence. But I think now, more than ever, we can write something we can all be proud of. GetAgrippa (talk) 12:19, 3 June 2011 (UTC)

Agree. I really think there is just too much detail in many of the descriptions that are best left to spin-off articles. If we are to embrace and include all the news ideas in this article, then I think we must strive for concision. mezzaninelounge (talk) 12:43, 3 June 2011 (UTC)
I think Thompsma is right on center about morphology. Phenotype is exactly what Mendel and Darwin were addressing, and much of the early advances (to the present)are morpological. I remember how logical and obvious evolution became from taking comparative anatomy decades ago, then evo-devo logically follows course extending the same ideas to development. The three-spine stickle back fish supermodel examines phenotypes, genetcs, organismic interactions, and environmental influences. None by themselves is explanatory but all together tell a story. I think this is key to Thompsma's suggestions. I always liked Gould's notion of a bauplan. We need a bauplan to glue everything together. GetAgrippa (talk) 23:03, 3 June 2011 (UTC)
Agreed GetAgrippa - this is exactly what is needed. This article has gotten outta hand and stagnant. Perhaps it might be best to start a scratch page and go from there? It will be a huge amount of work and a lot of hurdles to get the editors in here to agree. However, I think this could be accomplished. If you would like to start this up - I would be willing to poke in and assist. With a lot of work - I think a much improved article could be put together.Thompsma (talk) 23:20, 3 June 2011 (UTC)
Should the draft page be made on a user's page or can it be a subsection of this talk page? e.g., Talk:Evolution:New Draft. mezzaninelounge (talk) 21:53, 13 June 2011 (UTC)

Evolution of mutation rates: delete or move?

Since many seem to think the article is too long, I looked through it for things that look too specialised and out of place. Paragraph 2 under variation - mutation stands out to me. It summarises theories regarding the evolution of mutation rates. This is fairly arcane for a general reader, and there is no scientific consensus anyway. I suggest spinning it off as a stub for a new article on Evolution of mutation rate. Alternatively, the material can probably be merged into evolvability. Either way, I support moving it off the main evolution page. What do others think? Joannamasel (talk) 21:53, 6 June 2011 (UTC)

Sounds fine to me. mezzaninelounge (talk) 22:13, 6 June 2011 (UTC)
I moved it to mutation rate. --Ettrig (talk) 16:52, 7 June 2011 (UTC)
sounds fine to me. fwiw, in compsci this is called "meta-evolution". Kevin Baastalk 19:54, 7 June 2011 (UTC)
There is an interesting article called Genetic Architecture related to genotype-phenoypte maps. It also includes evovability and also mutational robustness. I never realized the article existed. The idea of mutational robustness is interesting-phenotype persistence despite mutations so it counters evolvability. GetAgrippa (talk) 19:24, 8 June 2011 (UTC)

Intelligent Design in the see also section

I have added Intelligent Design in the see also section. This does not create system where the page gives undo weight to Intelligent Design. It is included because both topics explain the concept of how life was created and came to be the way it is today. The see also section of Intelligent Design contains links to Evolution (added by me) and Flying Spaghetti Monster. Ryan Vesey (talk) 14:53, 11 June 2011 (UTC)

I'm deleting it again, because ID is of only marginal significance to the topic of this article. Obviously, you never even took the time to read this article because it has NOTHING whatsoever to do with "how life was created". Sorry, you addition does indeed violate WP:DUE WP:POV. Dominus Vobisdu (talk) 14:58, 11 June 2011 (UTC)
(EC):I disagree with the inclusion as the two topics are not actually related. Evolution is a scientific explanation for the changes in living organisms after the appearance of life on Earth. ID is a mess of politico-religious nonsense attempting to describe how life on Earth began, which is a completely different subject. The two only appear related because ID was developed in the USA as an attempt to end-run around the U.S. Constitution and teach religion in public schools. There is no rational reason to conflate the two here. Doc Tropics 15:03, 11 June 2011 (UTC)
Would creationism be a more applicable term? Ryan Vesey (talk) 15:08, 11 June 2011 (UTC)
No, it wouldn't. For the exact same reasons that ID is not applicable. This is a science article. Religious topics are only of marginal significance here, as explained in the text of the article. ID, creationism and Creation Science are religious views without anything of scientific merit to say on the topic of evolution. Mentioning them in this section would violate WP:DUE and WP:NPOV. Dominus Vobisdu (talk) 15:26, 11 June 2011 (UTC)
Whatever Ryan Vesey (talk) 15:27, 11 June 2011 (UTC)
And your response is telling, isn't it? OrangeMarlin Talk• Contributions 16:52, 11 June 2011 (UTC)
And your response is useful, isn't it? Ryan Vesey (talk) 16:57, 11 June 2011 (UTC)
My above response of "whatever" was, in essence, a shorter way of stating that I realize that the page, as it exists right now, is what will remain. Rather than continue to argue for my personal beliefs, I am backing away from the discussion. Other editor can please consider this discussion closed. Ryan Vesey (talk) 17:11, 11 June 2011 (UTC)

I notice that both intelligent design and creationism are included in the social and cultural responses section; does this solve the problem? Abtract (talk) 16:16, 11 June 2011 (UTC)

With some reluctance, but out of a respect for logic, I guess I have to point out that intelligent design is by its own account supposed to explain patterns in nature which look "designed", so not only the origin or initiation of life, but also the origin of the diversity of species. Part of the problem here is that compared to normal biology, if we take ID seriously it basically equates the origin of diversity with the origin of life, thus ignoring an important distinction which biology needs to make, and which we on WP need to make. (Yes I know, sometimes it allows for "micro evolution" but this does not remove the problem.) Anyway, coming to practical advice, I think there are reasons to mention ID as a kind of adjunct to creationism, and these relate to a movement or movements opposed to the concept of evolution (and I'd say say science). That there is such opposition to evolution is mentioned, and should be mentioned, because it is notable. But discussing it at length seems problematic, partly simply because this article is already very long, and secondly because pop culture can no doubt invent an almost infinite number of variations on the basic theme of not being comfortable with the theory of evolution, and we can't fill this article with too much about them all.--Andrew Lancaster (talk) 16:40, 11 June 2011 (UTC)
So just to make it clear, yes, I think Abtract has the solution.--Andrew Lancaster (talk) 16:41, 11 June 2011 (UTC)
Recent debate on this: []

PART X IS THERE A PLACE FOR INTELLIGENT DESIGN IN THE PHILOSOPHY OF BIOLOGY?

  • 19 There Is a Place for Intelligent Design in the Philosophy of Biology: Intelligent Design in (Philosophy of) Biology: Some Legitimate Roles. by Del Ratzsch
  • 20 There Is No Place for Intelligent Design in the Philosophy of Biology: Intelligent Design Is Not Science Francisco. by J. Ayala 364
The first author has an interesting point: "The question then may not be, “Is there a place for intelligent design in biology?” but, rather, “Exactly what and how essential is that place?”" In terms of the SETI program looking at cosmic phenomena - scientists should remain agnostic and there are some interesting thoughts that could go into this, but let's all be honest here. If there was an honest discourse on intelligent design in scientific terms - there wouldn't be any problem with this as an idea worthy of consideration. However, we all know that it is a ruse - creationism masquerading as science. It is hardly worth mention, definitely not worth a see also link, and I agree with Andrew Lancaster. Once again, however, this article needs to be gutted and re-written. In my opinion it does not deserve featured article status. The length of the article is not a problem - the content is. If the presentation wasn't so prescriptive it could better serve to counteract the intelligent design movement. In many respects the content of this article does a great disservice to the science because it is so narrowly focused on genes as the ultimate case for evolution while ignoring the tomes of science that have described evolution otherwise.Thompsma (talk) 21:07, 13 June 2011 (UTC)
While the philosophical discussion supplied is indeed interesting it is important to remember Intelligent Design was specifically fabricated for one purpose...

Shorten the history section?

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