scrappy Posted March 22, 2009 Posted March 22, 2009 Many people regard natural selection (NS) as the engine that drives Darwinian evolution. Perhaps the metaphor is useful, maybe even helpful, but is it biologically correct? Is it even fair to say that biological evolution has an engine that drives it somewhere? Firstly, let’s define “evolution” in the Darwinian sense: It means “decent with modification,” arising from the Malthusian principle that more offspring are produced by a population than can be sustained by its habitat (or environment). Secondly, lets’ define “natural selection” in the Darwinian sense: It means an occurrence of differential reproductive success amongst the individuals of a population. That’s all it is. And for that reason I think it was a mistake to call it “selection.” Selection implies a proactive inclination, something like intent—almost a deification of “decent with modification.” Maybe that’s where all the ambiguity about Darwinian evolution got started. The word Darwin should have used instead is “elimination”—“natural elimination” (NE)—which I think takes away the suggestion of intent: A portion of a population might be crushed by falling rocks, and we might be more accurate to call it NE than NS, because rocks can eliminate but they can’t select. I don’t see NS (my NE) as the only “driver” of evolution, if the metaphor works. NS is a consequence of something else and plays almost a passive role. Yet NS is very important to many evolutionary processes, if indeed it is a “process.” (Another issue.) There are five “drivers,” if you will, of neo-Darwinian evolution, or decent with modification at the genomic level: 1. genetic mutation—digital disruptions of genetic code 2. gene flow—digit code moving laterally from one genome to another 3. Random genetic drift—bottlenecking and the founder effect 4. Sexual selection—preferential mating 5. Natural selection—differential reproductive success. This thread is proposed to clarify the meaning of NS. (I would have posted this on the "Evolution Confusion" thread, but it seemed to drag it OT.) I would welcome any comments or criticism.
CharonY Posted March 22, 2009 Posted March 22, 2009 Who ever stated that NS is the engine of evolution? Normally it is regarded as a shaping force, if anything. Also neo-Darwinism is the old theory of evolution, which refuted Lamarckian inheritance. It did not, e.g. integrate genetics into the theory, as the modern synthesis does. As such it does not make much sense to discuss Darwinism or neo-Darwinism in this context. Note: not everything with "neo" in it is new in absolute terms.
Mokele Posted March 22, 2009 Posted March 22, 2009 The word Darwin should have used instead is “elimination”—“natural elimination” (NE)—which I think takes away the suggestion of intent Two problems, one minor, one major: Minor - 'elimination' still implies agency or activity - someone doing the elimination. Major - it's wrong. While in r-selected species (high # offspring, low survival rate), elimination may occur, a large portion of differential fitness is simply differential mating success and # of offspring. 'Death' is irrelevant - while dead animals don't breed, an animal which is alive but lacks offspring has the same fitness, zero. There are five “drivers,” if you will, of neo-Darwinian evolution, or decent with modification at the genomic level: 1. genetic mutation—digital disruptions of genetic code 2. gene flow—digit code moving laterally from one genome to another 3. Random genetic drift—bottlenecking and the founder effect 4. Sexual selection—preferential mating 5. Natural selection—differential reproductive success. The influences of these factors (and others, such as founder effect) are well known.
scrappy Posted March 22, 2009 Author Posted March 22, 2009 Who ever stated that NS is the engine of evolution? Normally it is regarded as a shaping force, if anything. Also neo-Darwinism is the old theory of evolution, which refuted Lamarckian inheritance. It did not, e.g. integrate genetics into the theory, as the modern synthesis does. As such it does not make much sense to discuss Darwinism or neo-Darwinism in this context. Note: not everything with "neo" in it is new in absolute terms. Nor is everything in "the modern synthesis" modern. What do you have that's better than neo-Darwinism? Merged post follows: Consecutive posts mergedTwo problems, one minor, one major: Minor - 'elimination' still implies agency or activity - someone doing the elimination. As I said above, rocks can't select, but they can eliminate. Major - it's wrong. While in r-selected species (high # offspring, low survival rate), elimination may occur, a large portion of differential fitness is simply differential mating success and # of offspring. 'Death' is irrelevant - while dead animals don't breed, an animal which is alive but lacks offspring has the same fitness, zero. You are correct about differentiating r-selection from k-selection. My remarks apply mainly to k-selection. There are five “drivers' date='” if you will, of neo-Darwinian evolution, or decent with modification at the genomic level: 1. genetic mutation—digital disruptions of genetic code 2. gene flow—digit code moving laterally from one genome to another 3. Random genetic drift—bottlenecking and the founder effect 4. Sexual selection—preferential mating 5. Natural selection—differential reproductive success.[/quote'] The influences of these factors (and others, such as founder effect) are well known. Well, please note that the founder is covered above in #3. What others your could mention that are so "well known"?
Mokele Posted March 22, 2009 Posted March 22, 2009 Nor is everything in "the modern synthesis" modern. What do you have that's better than neo-Darwinism? Evo-Devo is revolutionizing how we think about evolution, along with advances in the understanding of phenomena like epigenetics. There's no "super-new-synthesis" yet, but I figure in 10-20 years, we'll have advanced enough to justify a new stab at it. As I said above, rocks can't select, but they can eliminate. How? Rocks can't select *or* eliminate, all they can do is be selected or be eliminated. I think the wording is a non-issue. This is the first I've heard anyone bring it up, either in science or from creationists. If even they can figure out that natural selection doesn't imply active agency, I think it's not really that important. You are correct about differentiating r-selection from k-selection. My remarks apply mainly to k-selection. So, you want to switch a perfectly good term that applies to both for an inferior term that only applies to some? How is this a good idea? Also, your term doesn't apply well to *either*. In both r-selected and k-selected species display unequal fitness due to both death and failure to reproduce. Humans (strongly k-selected) display both pre-reproductive mortality and failure to reproduce without dying. Frogs (strongly r-selected) also display both pre-reproductive mortality and failure to reproduce without dying. So what possible use is your new term? Well, please note that the founder is covered above in #3. What others your could mention that are so "well known"? Inbreeding, hybridization, horizontal gene transfer, epigenetics, developmental effects, gene duplication.
CharonY Posted March 22, 2009 Posted March 22, 2009 Nor is everything in "the modern synthesis" modern. What do you have that's better than neo-Darwinism? You are aware that neo-Darwinism is a term coined by Romanes and did not contain essential elements as genes for instance. Some erroneously refer modern evolutionary theories as neo-darwinism, but that is incorrect. There's no "super-new-synthesis" yet, We are partially there, already. Some of the basic tenets of the modern synthesis (including species concept and organization of genomes) have been pretty much refuted by genome-based analyzes. It is true however, that to date there are only rather few tentative attempts to integrate it into a newer, sometimes strikingly referred to as postmodern, theory. Otherwise I agree completely agree with Mokele.
Mokele Posted March 22, 2009 Posted March 22, 2009 We are partially there, already. Some of the basic tenets of the modern synthesis (including species concept and organization of genomes) have been pretty much refuted by genome-based analyzes. It is true however, that to date there are only rather few tentative attempts to integrate it into a newer, sometimes strikingly referred to as postmodern, theory. Agreed; I think the 'big leap' will come when we integrate development with gene-based approaches, so we can understand the underlying evolutionary processes acting on complex phenotypic traits such as limb morphology and behavior. Plus, I'm impatient to be able to use genetic methods to cause large phenotypic changes in order to examine their consequences.
scrappy Posted March 23, 2009 Author Posted March 23, 2009 Inbreeding, hybridization, horizontal gene transfer, epigenetics, developmental effects, gene duplication. 1. Inbreeding is a form of random genetic drift 2. Hybridization and horizontal gene transfer are forms of gene flow. 3. Epigenetics role in evolution is not yet resolved 4. Developmental effects can often be explained genetically* 5. Gene duplication—what is that? Meiosis? Mitosis? Mutation? *I purchased and read Mary Jane West-Eberhard's book Developmental Plasticity and Evolution to learn about evo devo. I found many, many of her assertions to be explainable using the genetics put forth by Richard Dawkins. To me, altruistic and selfish gene theories offer better explanations for her proclaimed evo-devo evolutionary events...but just to me. As such, I'm not a big fan of evo devo
Mokele Posted March 23, 2009 Posted March 23, 2009 1. Inbreeding is a form of random genetic drift No, actually, it isn't. Inbreeding will not alter the total allele frequency in a population, only make individuals more homozyous, while genetic drift will alter total allele frequency. 2. Hybridization and horizontal gene transfer are forms of gene flow. Yes and no. Gene flow typically refers to transfer between populations of the same species. Horizontal gene transfer and hybridization do move genes, but the issues of interaction of long-separated genes complicate things. 3. Epigenetics role in evolution is not yet resolved Precisely. We need to know more and incorporate it. 4. Developmental effects can often be explained genetically**I purchased and read Mary Jane West-Eberhard's book Developmental Plasticity and Evolution to learn about evo devo. I found many, many of her assertions to be explainable using the genetics put forth by Richard Dawkins. To me, altruistic and selfish gene theories offer better explanations for her proclaimed evo-devo evolutionary events...but just to me. As such, I'm not a big fan of evo devo I think you missed the point, then. Evo-devo deals with how phenotype can change as the result of changes in gene regulation, such as adding body segments or altering expression. Dawkins' 'extended phenotype' is a result of evo-devo, not an alternative. Consider, for instance, snakes. Traditional gene-based systems cannot explain them, but when you look in a developmental perspective, it's obvious that while the genes are the same, the expression has been altered to produce an incredibly long series of thoracic segments. 5. Gene duplication—what is that? Meiosis? Mitosis? Mutation? You know crossing over, where homologous chromosomes swap information? Well, it doesn't always match up perfectly, and as a result, one chromosome winds up missing genes, another with extra copies. Obviously the organism missing the gene will be at a severe disadvantage, but the organism with a duplicate gene will have a 'spare' copy, which is free to mutate into new functions. Often, the gene just degrades, but sometimes it results in a new, functional gene. Over time, you get 'gene families', all related by duplication and subsequent modifications. Hemoglobins are an excellent example of this. Occaisionally, due to errors in meiosis or mitosis, whole-genome duplication may occur, allowing every single gene to have a 'spare', including vital developmental genes. It has been suggested that events of whole genome duplication may be responsible for many of the 'leaps' in vertebrate evolution such the origin of vertebrates themselves, the origin of gnathostomes, and the incredibly complex jaws of teleosts. Mokele
scrappy Posted March 23, 2009 Author Posted March 23, 2009 No, actually, it isn't. Inbreeding will not alter the total allele frequency in a population, only make individuals more homozyous, while genetic drift will alter total allele frequency. What results from random genetic drift is inbreeding, which can alter allele frequency. There is nothing special about inbreeding that sets it outside the definition of drift. Evo-devo deals with how phenotype can change as the result of changes in gene regulation, such as adding body segments or altering expression. Dawkins' 'extended phenotype' is a result of evo-devo, not an alternative. I see it differently. I see the extended phenotype—Dawkins' argument, which I have studied to a fair degree—not as a result of evo-devo, but as an alternative explanation. Consider, for instance, snakes. Traditional gene-based systems cannot explain them, but when you look in a developmental perspective, it's obvious that while the genes are the same, the expression has been altered to produce an incredibly long series of thoracic segments. No, I don't agree. A snake's hox genes may be the same as other vertebrates, but I'm not yet ready to agree that selfish/altruistic genes "strategies" are functionless in your case of snakes. You know crossing over, where homologous chromosomes swap information? Well, it doesn't always match up perfectly, and as a result, one chromosome winds up missing genes, another with extra copies. Obviously the organism missing the gene will be at a severe disadvantage, but the organism with a duplicate gene will have a 'spare' copy, which is free to mutate into new functions. Often, the gene just degrades, but sometimes it results in a new, functional gene. Over time, you get 'gene families', all related by duplication and subsequent modifications. Hemoglobins are an excellent example of this. Occaisionally, due to errors in meiosis or mitosis, whole-genome duplication may occur, allowing every single gene to have a 'spare', including vital developmental genes. It has been suggested that events of whole genome duplication may be responsible for many of the 'leaps' in vertebrate evolution such the origin of vertebrates themselves, the origin of gnathostomes, and the incredibly complex jaws of teleosts. Yes, I, too, am fascinated with crossing over and its implications to genetic alteration and evolution. And I agree that it might affect "vital developmental genes." But does that serve well your position in this debate? You're agreeing, essentially, that developmental genes are the heart of development, which the dispels the need for evo-devo.
Mokele Posted March 23, 2009 Posted March 23, 2009 What results from random genetic drift is inbreeding, which can alter allele frequency. There is nothing special about inbreeding that sets it outside the definition of drift. Wrong. I suggest this book. It explains the difference between the two using Hardy-Weinberg equations, and they are *very* different. Drift is random sampling error between generations, while inbreeding is a type of assortative mating which increases individual and population-wide homozygosity. Both can be expressed in purely mathematical terms, and the results are not equivalent. I see it differently. I see the extended phenotype—Dawkins' argument, which I have studied to a fair degree—not as a result of evo-devo, but as an alternative explanation. They are the same. Dawkins himself, and any reputable biologist, will tell you that genes become phenotype via development, and that alterations to developmental genes or their expression can have far greater impacts than altering the gene for fur color. No, I don't agree. A snake's hox genes may be the same as other vertebrates, but I'm not yet ready to agree that selfish/altruistic genes "strategies" are functionless in your case of snakes. What do selfish/altruistic genes have to do with it? My point is that the genes didn't change, only their expression, pointing out the role non-gene hereditary elements (such as regulatory regions) and development in evolution. And we actually know this - we've sequenced the relevant HOX genes and mapped their expression in the snake embryo. Yes, I, too, am fascinated with crossing over and its implications to genetic alteration and evolution. And I agree that it might affect "vital developmental genes." But does that serve well your position in this debate? You're agreeing, essentially, that developmental genes are the heart of development, which the dispels the need for evo-devo. No, I'm merely arguing that your position, in the initial post, is insufficient and inaccurate. Evo-devo is one reason. Fecundity differences are a second. Gene duplication is a third. And developmental genes *are* important, but so are non-coding gene regulatory regions that control their expression. Seriously, you will not find any biologist *anywhere* who disputes the importance of gene regulation. And evo-devo is *about* developmental genes and their expression. That's like saying my assertion that wheels are cool translates to an opposition to cars. Look, I appreciate your enthusiasm for the subject, but you *really* need to catch up on recent development. The book I linked to is very current and very understandable, and should help you realize just what we're talking about.
scrappy Posted March 23, 2009 Author Posted March 23, 2009 Wrong. I suggest this book. It explains the difference between the two using Hardy-Weinberg equations, and they are *very* different. Drift is random sampling error between generations, while inbreeding is a type of assortative mating which increases individual and population-wide homozygosity. Both can be expressed in purely mathematical terms, and the results are not equivalent. But aren’t the basic principles of drift served in both cases? Dawkins himself, and any reputable biologist, will tell you that genes become phenotype via development, and that alterations to developmental genes or their expression can have far greater impacts than altering the gene for fur color. Dawkins will tell you that genes do not become phenotypes, instead they code for phenotypes. Dawkins makes a good case for the fact that genes are not stereochemical with their proteins, but instead they require transcription and translation by RNA operators. As such, Dawkins, Hamilton, et al. would discourage the image of a gene as an analog “blueprint” of a protein, but instead it is a digital code for it. I could debate you on the precise meaning of drift, including its mathematical formulations, and on the other functional categories of “drivers” (I prefer “agencies”) of evolution. We could go on about evo-devo, too, and I’m sure I’d learn something from you. But it’s not on topic here. Perhaps you’d like to start a thread on it. Let’s stick to the meaning of “natural selection.” Why do you think fecundity is not one sex’s expression of NS? It’s only different because it can’t be applied to males (in k-selection scenario). Look, I appreciate your enthusiasm for the subject, but you *really* need to catch up on recent development. The book I linked to is very current and very understandable, and should help you realize just what we're talking about. I'm sure you can teach me something. I have read a lot of books on evolution, and I have read some of Futuyma, too. What impresses me most is that many authors still disagree on even such an important matter as the precise difference between microevolution and macroevolution. But let's stick to NS on this thread.
Mokele Posted March 23, 2009 Posted March 23, 2009 But aren’t the basic principles of drift served in both cases? No, drift is sampling error, and alters the overall allele frequency in the population. Inbreeding, on the other hand, keeps the same allele frequency, but just alters the distribution so that more individuals than expected are homozygous (that's actually how we measure inbreeding - percent of expected heterozygosity). Why do you think fecundity is not one sex’s expression of NS? It’s only different because it can’t be applied to males (in k-selection scenario). No, I *do* think fecundity is part of natural selection. My objection was that your term, 'natural elimination' focuses exclusively on mortality and ignores fecundity differences.
scrappy Posted March 23, 2009 Author Posted March 23, 2009 No, drift is sampling error, and alters the overall allele frequency in the population. Inbreeding, on the other hand, keeps the same allele frequency, but just alters the distribution so that more individuals than expected are homozygous (that's actually how we measure inbreeding - percent of expected heterozygosity). Not bad. I'll have to study on it. No, I *do* think fecundity is part of natural selection. My objection was that your term, 'natural elimination' focuses exclusively on mortality and ignores fecundity differences. Perhaps. Mokele, a question: Do you thing NS "happens" (i.e., the implementation of that agency) at the phenotype level or the genotype level? or is it a chicken-or-egg issue? Here's what M. J. West-Eberhard says about it in her book Developmental Plasicity and Evolution (2003,p. 3): "Here I put the flexible phenotype first, as the product and the object of selection, and examine the consequences for the genetic theory of evolution." Is that statement consistent with your opinions on the matter?
Mokele Posted March 24, 2009 Posted March 24, 2009 Mokele, a question: Do you thing NS "happens" (i.e., the implementation of that agency) at the phenotype level or the genotype level? Phenotype, definitely. Selection can act on non-genetic phenotype, such as learned behavior, resulting in a failure to change gene frequency. Plus, well, a cheetah doesn't catch a gazelle based on PCR results - it catches it based on speed. Genotype + environment = phenotype. Phenotype is selected upon, resulting in changes in population genetic structure.
scrappy Posted March 24, 2009 Author Posted March 24, 2009 Phenotype, definitely. Selection can act on non-genetic phenotype, such as learned behavior, resulting in a failure to change gene frequency. Plus, well, a cheetah doesn't catch a gazelle based on PCR results - it catches it based on speed. Genotype + environment = phenotype. Phenotype is selected upon, resulting in changes in population genetic structure. I appreciate your answer. I know it is an arguable position. But if Dawkins and Hamilton hadn't gotten to me so convincingly I might capitulate. Here's my trouble this concept: Genotypes are not additively complicit with the environment to produce the phenotypes. All genes and genotypes can do is survive as best they can from one generation to the next. And their survival is assured when (in k-selection) reproductive success of the host individuals is accomplish. Phenotypes (most of them) don't move as analogs across that fertilization boundary—only their genotypes (digital codes) cross that boundary. I see NS operating precisely at that boundary, because that boundary is where differential reproductive success amongst individuals of a population is decided. Therefore, I think NS operates on the code and not on the analog. On learning as evo-devo: Leaning is a gene-limited operation, I think. To me, it's not merely a phenotypical, analog thing. You need good genes to learn well; the phenotypes that permit learning are predisposed by the limits of their genotypes.
Mokele Posted March 24, 2009 Posted March 24, 2009 Here's my trouble this concept: Genotypes are not additively complicit with the environment to produce the phenotypes. All genes and genotypes can do is survive as best they can from one generation to the next. And their survival is assured when (in k-selection) reproductive success of the host individuals is accomplish. Phenotypes (most of them) don't move as analogs across that fertilization boundary—only their genotypes (digital codes) cross that boundary. I see NS operating precisely at that boundary, because that boundary is where differential reproductive success amongst individuals of a population is decided. The problem is you're confusing the tallying of scores with the race itself. What determines which animal gets to reproduce and which doesn't? It's not genes - nature doesn't peer into the genetic code and decide who gets eaten. It's phenotype - who is faster, stronger, better at hiding, produces more eggs, etc. Learning is a poor example, admitedly, so I'll try a different one. Snapping turtles lay a LOT of eggs, buried in a hole, and let ambient nest-site temperatures deal with incubation. We know that hatchling turtles from the same parents raised in cool nests not only are slower moving than their hot-nest kin, but that these differences persist over at least 6 months, possibly more (possibly the entire lifespan of the turtles). This is a particular problem because the baby turtles are subjected to heavy predation, and snappers have minimal belly shells that offer little protection (they also cannot withdraw their heads). So, here you have a situation where environment affects phenotype, and thus selection, independent of genotype. All baby turtles are equally impeded by a cool nest, and the mother cannot control nest temperature (it's influenced very strongly by weather, even in optimal sites). If genotype was the level of selection, cold and warm babies with 'fast' genotypes should be selected equally, but they aren't. Phenotype (speed) determines who lives and who dies, regardless of the genotype. A fast-genotype baby from a cold nest will be slower and is more likely to be eaten than a slow-genotype baby from a warm nest. Another excellent example is from reticulated pythons. The males are a "mere" 14 feet long, but the females can exceed 27 feet in length, weighing hundreds of pounds, all for one reason - bigger snakes lay more eggs (egg size is mostly fixed). But size is determined by food availability, and even a baby snake with genes to make it a good hunter will not grow as large without sufficient food, to the point of outright stunting - a baby retic can grow from 2 feet (hatching) to 12 feet in a year if it gets all the food it can process, but will remain stunted at 2 feet indefinitely (and in permanent sexual immaturity) with 'survival rations'. Their genotype is important, but the availability of prey is even moreso. Yes, genotype builds phenotype, along with some environmental factors, and selection results in changes in gene frequency, but it's the performance capabilities of phenotypes which are acted on by natural selection.
scrappy Posted March 24, 2009 Author Posted March 24, 2009 The problem is you're confusing the tallying of scores with the race itself. Or I could say the problem is that tallying the score is what NS actually is, while the race is what happens before there is any scoring. What determines which animal gets to reproduce and which doesn't? It's not genes - nature doesn't peer into the genetic code and decide who gets eaten. It's phenotype - who is faster, stronger, better at hiding, produces more eggs, etc. Not at the moment when NS is measurable: i.e., that moment when there is an occurrence of differential reproductive success amongst individuals of a population. That moment (in k-selected pops.) is fertilization. And, at that moment, the phenotypes are all but non-existent. So, here you have a situation where environment affects phenotype, and thus selection, independent of genotype. No. That is not what NS is. NS is an occurrence of differential reproductive success amongst individuals of a population. You’re talking about physical events that affect allele distribution; I’ll agree to that. But NS is not precisely active in the context you offered, because you couldn’t observe NS until the you saw which alleles (genotypes) made the jump successfully at the moment of fertilization. I don’t think predation, for example, is selective, per se, but the consequences of it, as measure by an occurrence of differential reproductive success amongst individuals of a population would fit the definition of NS. And that would require genotypes to carry the load, because the phenotypes are mostly unexpressed. Yes, genotype builds phenotype, along with some environmental factors, and selection results in changes in gene frequency, but it's the performance capabilities of phenotypes which are acted on by natural selection. No. That is not what NS is. NS is an occurrence of differential reproductive success amongst individuals of a population. I think we may have a bit of a chicken-or-egg argument here.
Mokele Posted March 24, 2009 Posted March 24, 2009 Natural selection is not a result, it's a process. If you define NS as "an occurrence of differential reproductive success amongst individuals of a population", you've defined drift and founder effect as natural selection, since both result in differential reproductive success. Differential reproductive success can happen as a result of natural selection, but natural selection itself *is* the process of organisms living and dying and breeding, all of which acts on phenotype. Consider the race again, with cars, specifically. Each car is built from a set of blueprints, but the winner is not determined from examining the blueprints, but rather on the speed of the resulting car. It's the winning car's blueprints that are used to make the next generation of racecars, but the actual determinant of who won was based on the performance of constructed cars. A construction error or deviation from plans due to resource shortages may doom a good blueprint. That's my problem with this "all genes all the time" crap - it ignores the fact that genes build organisms, and that the performance of the organism is what determines how many offspring it has or whether it survives.
scrappy Posted March 24, 2009 Author Posted March 24, 2009 Natural selection is not a result, it's a process. A falling rock is not NS, but it might lead to differential success amongst individuals of a ppulation, which is NS. If you define NS as "an occurrence of differential reproductive success amongst individuals of a population", you've defined drift and founder effect as natural selection, since both result in differential reproductive success. 1. The founder effect is, in fact, drift. 2. Drift is not selective, and therefore it is not NS. Differential reproductive success can happen as a result of natural selection, but natural selection itself *is* the process of organisms living and dying and breeding, all of which acts on phenotype. No. Diferential reproductive success... is NS. Consider the race again, with cars, specifically. Each car is built from a set of blueprints, but the winner is not determined from examining the blueprints, but rather on the speed of the resulting car. It's the winning car's blueprints that are used to make the next generation of racecars, but the actual determinant of who won was based on the performance of constructed cars. A construction error or deviation from plans due to resource shortages may doom a good blueprint. Bad analogy, because genotypes are not "blueprints" of their phenotypes. Genotypes look nothing like their phenotypes. Genotype are only code for their phenotypes. That's my problem with this "all genes all the time" crap - it ignores the fact that genes build organisms, and that the performance of the organism is what determines how many offspring it has or whether it survives. Crap? Genes don't "build" organisms. Genes only code for phenotypes. The ribosomes, if anything, build the organism.
Mokele Posted March 25, 2009 Posted March 25, 2009 A falling rock is not NS, but it might lead to differential success amongst individuals of a ppulation, which is NS. Really? So the fact that *everyone* else defines NS as a process, not a result, doesn't phase you at all? From now on, I'm going to call genes flugles. Because I can. 2. Drift is not selective, and therefore it is not NS. It is according to your definition. No. Diferential reproductive success... is NS. So drift and founder effect? I'm not just being pedantic - the problem with defining NS as a result is that there are other mechanisms that lead to the same result. What's walking? Is walking the place you wind up, or the process by which you got there? Bad analogy, because genotypes are not "blueprints" of their phenotypes. Genotypes look nothing like their phenotypes. Genotype are only code for their phenotypes. Genes don't "build" organisms. Genes only code for phenotypes. The ribosomes, if anything, build the organism. ::bangs head against wall:: And where do ribosomes come from? Do they get left in the cytoplasm overnight by the ribosome fairy if the cell has been good and not become cancerous? What determines what the ribosomes do? Do you think all genes are always produced all the time? What do they produce? When? Look, it's blatantly clear you don't actually understand what you're talking about. I suggest you take some time to familiarize yourself with the subject in more detail before continuing.
scrappy Posted March 25, 2009 Author Posted March 25, 2009 A falling rock is not NS' date=' but it might lead to differential success amongst individuals of a population, which [i']is[/i'] NS. Really? So the fact that *everyone* else defines NS as a process, not a result, doesn't phase you at all? "Everyone"? Please prove your assertion. From now on, I'm going to call genes flugles. Because I can. You can call random genetic drift the same thing as natural selection, too, and you’ll look just as ridiculous. 2. Drift is not selective' date=' and therefore it is not NS.[/quote']It is according to your definition. You’ve got a lot work to do to catch up on cause-effect relationships of evolution. No. Diferential reproductive success... is NS. So [is?] drift and founder effect? I'm not just being pedantic - the problem with defining NS as a result is that there are other mechanisms that lead to the same result. What's walking? Is walking the place you wind up' date=' or the process by which you got there?[/quote'] If you continue to confuse drift with NS I don’t know how to help you and move on with this discussion. Bad analogy' date=' because genotypes are not "blueprints" of their phenotypes. Genotypes look nothing like their phenotypes. Genotype are only code for their phenotypes. Genes don't "build" organisms. Genes only code for phenotypes. The ribosomes, if anything, build the organism.[/quote'] ::bangs head against wall:: And where do ribosomes come from? Do they get left in the cytoplasm overnight by the ribosome fairy if the cell has been good and not become cancerous? What determines what the ribosomes do? Do you think all genes are always produced all the time? What do they produce? When? I’ll leave you to your “cytoplasm fairies.” If you still think genes are “blueprints” of proteins then I don’t know where you’ve been in the last few years. Maybe with the evo-devo fairies? Look, it's blatantly clear you don't actually understand what you're talking about. I suggest you take some time to familiarize yourself with the subject in more detail before continuing. My, oh, my! Aren’t we a bit insecure here. And you’re a moderator, too. Telling!
Sayonara Posted March 25, 2009 Posted March 25, 2009 My, oh, my! Aren’t we a bit insecure here. And you’re a moderator, too. Telling! You can have it from an administrator if you prefer: Look, it's blatantly clear you don't actually understand what you're talking about. I suggest you take some time to familiarize yourself with the subject in more detail before continuing.
lucaspa Posted April 15, 2009 Posted April 15, 2009 Firstly, let’s define “evolution” in the Darwinian sense: It means “decent with modification,” arising from the Malthusian principle that more offspring are produced by a population than can be sustained by its habitat (or environment). With all respect, you are confusing different parts of evolution. Yes, evolution is "descent with modification". One method of modification is natural selection. Part of what makes natural selection wor is the more offspring are produced by a population than can be supported by the environment. So you have attached a part of natural selection as part of the definition of evolution. Secondly, lets’ define “natural selection” in the Darwinian sense: It means an occurrence of differential reproductive success amongst the individuals of a population. That’s all it is. No, it's not. Here's where people need to read Darwin. If you are going to "define natural selection in the Darwinian sense", then you must use Darwin's definition of natural selection! So, let's put up Darwin's definition: "If, during the long course of ages and under varying conditions of life, organic beings vary at all in the several parts of their organization, and I think this cannot be disputed; if there be, owing to the high geometric powers of increase of each species, at some age, season, or year, a severe struggle for life, and this certainly cannot be disputed; then, considering the infinite complexity of the relations of all organic beings to each other and to their conditions of existence, causing an infinite diversity in structure, constitution, and habits, to be advantageous to them, I think it would be a most extraordinary fact if no variation ever had occurred useful to each beings welfare, in the same way as so many variations have occured useful to man. But if variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will will tend to produce offspring similarly characterized. This principle of preservation, I have called, for the sake of brevity, Natural Selection." [Origin, p 127 6th ed.] Now we can easily see that differential reproductive success is secondary. It's a result of natural selection. The primary focus of natural selection is the production of designs in living organisms. Natural selection is an unintelligent process for producing designs. Darwin deliberately used "selection" because "natural selection" was the artificial selection used by human breeders happening in nature. But you can see that Darwin emphasized preservation, not "elimination". The variations eliminated are not important, what is important are the variations preserved. A portion of a population might be crushed by falling rocks, and we might be more accurate to call it NE than NS, because rocks can eliminate but they can’t select. This is different. This is called "nonselective mortality". Being crushed by a rock does nothing to preserve the individual in the struggle for existence. Having quick reflexes to avoid the rocks in an area prone to frequent earthquakes is a trait that would be selected. There are five “drivers,” if you will, of neo-Darwinian evolution, or decent with modification at the genomic level: 1. genetic mutation—digital disruptions of genetic code 2. gene flow—digit code moving laterally from one genome to another 3. Random genetic drift—bottlenecking and the founder effect 4. Sexual selection—preferential mating 5. Natural selection—differential reproductive success. Congratulations on re-inventing the wheel! Have you ever heard of Hardy-Weinberg? That principle, based in Mendelian genetics, states that the frequency of an allele in a large population will remain the same from generation to generation unless affected by outside influences. What you did was list the 5 things that will disturb a Hardy-Weinberg equilibrium. BUT, the only one of those that will produce the designs we see in plants and animals is natural selection. Instead of trying to confuse yourself and others, I suggest you just do a bit of elemental reading about evolution. I suggest Evolutionary Biology by Douglas Futuyma. BTW, gene flow is not "digit code moving laterally from one genome to another" but rather individuals from outside the population mating with individuals within the population. "digit code moving laterally from one genome to another" is "lateral gene transfer" in microorganisms.
Recommended Posts