Mutation

What is your definition of "beneficial"? I ask because if you're just going to define "beneficial" in such a way that no mutation could ever be beneficial, then there's no point in talking to you, right?Here's a start - biologists define "beneficial" as any mutation that allows an organism to generate more survivng progeny in a given environment. There's certainly plenty of examples of that: Are Mutations Harmful?Now, do you agree with this definition? If not, why not? And if not, why should we use your definition over the more useful biological one?

...because of mutation.Remember that mutation is random and not generally driven by environment. Natural selection selects for traits that already exist; it doesn't create mutations to select.The trait was selected for because the environment changed. You're right that the trait already existed before the environmental change; the reason it existed is because of mutation. Obviously. But the fact that it existed in the population at all was due to a mutation.

I don't think that's what he meant - I think by "dominant" he meant that the frequency of that allele in the population increases so that it's the most common. I don't think he was actually referring to genetic dominance.Insofar as he meant that evolution is a process by which some alleles increase in frequency within a population's gene pool as a result of natural selection, I think that's the view of every evolutionist, not just many or most.

If he doesn't know what genetic dominance refers to, he's not going to understand how you misunderstood him. I was just trying to facilitate understanding on both sides. I think it's safe to say that sometimes we have to make allowances for people who may not be familiar enough with the sciences to get the terms right. At which point it's the defining feature of that population, which is what he was saying.Look, the guy's a crank, I'm sure, but misrepresenting what he was saying doesn't serve anybody.

Well-developed throats, large areas of the brain devoted to language, upright posture, thin body hair, large male genitals, etc. Those are the key ways that evolution occurs, yes. Reproductive isolation is the key way that new species form. Yeah, you're slightly wrong.Mutations don't create new species by themselves. It has to be mutation occuring in a situation of reproductive isolation. An isolated subpopulation accumulates mutations that aren't shared with the main population until the subpopulation is no longer able to breed with the main population.At that point you have a new species. When did it happen? Well, that's about as hard to answer as "when did it start raining?" Speciation is the result of a process, not an event in itself. This is wrong. Most mutations have no effect on the organism. You might want to keep in mind that it's only the environment that determines whether or not a mutation is harmful, neutral, or beneficial.

Because that's the only observed mechanism for the introduction of genetic material into the gene pool of a population.The alternative is that humans have always had these genes because humans were created with them, but we've never observed a mechanism that can create an organism wholesale from scratch. No, they're quite common. You probably have between 50 and 500 (rough estimate) mutations of your very own. Obviously they're neutral ones, or else you'd notice. Then again there's the occasional human with a noticable mutation, like a lack of wisdom teeth. Sometimes that happens. But a beneficial mutation is one that allows that organism to leave more progeny than it's competitors. Therefore by definition the mutation will become more common because individuals with the mutation are outcompeting and outreproducing the individuals who lack it.Remember also that it isn't "muties vs. normals." The individuals without the mutation don't band together against the individual with it. They're competing against each other, too. All speciation happens as a result of reproductive isolation. Huh, I'm surprised you missed that; I thought I had been pretty clear about it.Evolution is when allele frequencies change within a gene pool. Speciation separates gene pools permanently (which can change allele frequencies.) Reproductive isolation interrupts gene flow, which allows speciation to occur. By selection. Beneficial mutations are mutations that are selected for. Harmful mutations are mutations that are selected against. Of course, it's not like the environment is picking and choosing, any more than the roulette wheel "chooses" where the ball lands. Selection is just the name we give to the observation that organisms adapted to their environment tend to leave more offspring than the ones that don't.For instance - what if you had a mutation that gave you thick, insulating fur? Is that a beneficial mutation or a harmful one? Kinda depends on whether you live at the North Pole or in Africa, doesn't it?

Any sequence of genetic code that you didn't inherit from either of your parents. People with no wisdom teeth. There's a number of mutations, I believe, that confer degrees of resistance to various diseases, like the gene for sickle-cell anemia. Certainly not. You have somewhere between 50 and 500 mutations of your very own, and I assume you have no reason to doubt your fertility? All mutations have the potential to do is change how protiens are created, because that's all genes do - code for protiens. Not exactly - it's generally possible, given a substantial enough mutation, to predict how it might interact with the environment. For instance in an environment dominated by nylon oglimers, a mutation allowing a bacterium to digest them is likely to be beneficial indeed. Ultimately, though, you have to go by the results - does that gene spread through the gene pool, or is it eliminated? Ask somebody with impacted wisdom teeth if not having them would be beneficial. In an environment of cooked, soft food leading to smaller jaws with less room for teeth, less teeth is beneficial indeed.The problem is that, as humans, we pre-empt natural selection. We don't allow selection to occur, so ultimately it's not possible to use "beneficial" properly in regards to human mutations. Human allele frequencies change in ways that have nothing to do with natural selection or adaption to environment. Evolution is the process by which allele frequencies within a gene pool change. Speciation is the process by which gene pools sepearate into separate pools.If you're not looking at evolution from the perspective of population genetics, you're not looking at it the right way. Organisms don't evolve. Only populations do. Mutations are novel gene sequences not inherited from either parent. Evolution is a change in allele frequencies. The source of new alleles is mutation, but mutation isn't responsible for the shift in frequency - that's a function of natural selection. It is safe to say that mutation + natural selection = evolution.

Perhaps you're right. Nonetheless I think it's useful to take a step back and consider what is really meant when we say "this gene codes for such-and-such." Otherwise one is liable to conflate the complexity of a structure with the complexity of the gene controlling it, which leads to dumb questions about how much complexity mutation can be the source of, etc.

With that caveat, I agree.

Again, it depends on environment. For people whose jaws are too small to support that many teeth, not having them is beneficial.But rememeber that humans are no longer subject to the stricter forms of natural selection. The only selection occuring on most humans is sexual selection, really. I don't have the stats, myself. I know that mine were removed, so clearly it would have been to my benefit to not have themat all. You're going to have to explain this. What would prevent a mutation from being passed on? The only mutations we're concerned about are the ones that happen to the fertilized zygote (or during the formation of the gametes in the parents gonands). Since the entire organism is composed of the decendants of that cell, every cell in the organism, including the gametes (well, the ones with the chromosome in question, which would be half of them) will contain the mutant gene.Where's the problem to heredity, here? I guess I don't understand your point. You can never take away environment. You can only change environment. An animal in a scientific pen is still in an environment.What would be arbitrary would be subjective judgements about what is beneficial or detrimental. Considering mutations in relationship to the environment is the only objective measure of the eventual success of a mutation. No... but mutations in your son could represent the evolution of the human population. Your son will always be himself. He'll only change insomuch as humans change throughout their lives. That change will never represent an evolution of your son. It's the difference between your son and you that represent the evolution of the human species. Or, confer resistance to disease or give the cell the capability to use a new substance as a metabolic fuel. Or do nothing at all. Again, you seem to be generalizing - because many mutations are harmful or even fatal, you seem to think they all must be. New species of fruitfly? We do that all the time, through reproducive isolation:

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5.3 The Fruit Fly Literature

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5.3.1 Drosophila paulistorum

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Dobzhansky and Pavlovsky (1971) reported a speciation event that occurred in a laboratory culture of Drosophila paulistorum sometime between 1958 and 1963. The culture was descended from a single inseminated female that was captured in the Llanos of Colombia. In 1958 this strain produced fertile hybrids when crossed with conspecifics of different strains from Orinocan. From 1963 onward crosses with Orinocan strains produced only sterile males. Initially no assortative mating or behavioral isolation was seen between the Llanos strain and the Orinocan strains. Later on Dobzhansky produced assortative mating (Dobzhansky 1972).

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5.3.2 Disruptive Selection on Drosophila melanogaster

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Thoday and Gibson (1962) established a population of Drosophila melanogaster from four gravid females. They applied selection on this population for flies with the highest and lowest numbers of sternoplural chaetae (hairs). In each generation, eight flies with high numbers of chaetae were allowed to interbreed and eight flies with low numbers of chaetae were allowed to interbreed. Periodically they performed mate choice experiments on the two lines. They found that they had produced a high degree of positive assortative mating between the two groups. In the decade or so following this, eighteen labs attempted unsuccessfully to reproduce these results. References are given in Thoday and Gibson 1970.

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5.3.3 Selection on Courtship Behavior in Drosophila melanogaster

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Crossley (1974) was able to produce changes in mating behavior in two mutant strains of D. melanogaster. Four treatments were used. In each treatment, 55 virgin males and 55 virgin females of both ebony body mutant flies and vestigial wing mutant flies (220 flies total) were put into a jar and allowed to mate for 20 hours. The females were collected and each was put into a separate vial. The phenotypes of the offspring were recorded. Wild type offspring were hybrids between the mutants. In two of the four treatments, mating was carried out in the light. In one of these treatments all hybrid offspring were destroyed. This was repeated for 40 generations. Mating was carried out in the dark in the other two treatments. Again, in one of these all hybrids were destroyed. This was repeated for 49 generations. Crossley ran mate choice tests and observed mating behavior. Positive assortative mating was found in the treatment which had mated in the light and had been subject to strong selection against hybridization. The basis of this was changes in the courtship behaviors of both sexes. Similar experiments, without observation of mating behavior, were performed by Knight, et al. (1956).

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From Observed Instances of SpeciationRemember, it's not the process of mutation alone that gives rise to new species. It's mutations accruing in a situation where gene flow is interrupted (reproductive isolation.) Here's one, from the same link:

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5.9.1 Coloniality in Chlorella vulgaris

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Boraas (1983) reported the induction of multicellularity in a strain of Chlorella pyrenoidosa (since reclassified as C. vulgaris) by predation. He was growing the unicellular green alga in the first stage of a two stage continuous culture system as for food for a flagellate predator, Ochromonas sp., that was growing in the second stage. Due to the failure of a pump, flagellates washed back into the first stage. Within five days a colonial form of the Chlorella appeared. It rapidly came to dominate the culture. The colony size ranged from 4 cells to 32 cells. Eventually it stabilized at 8 cells. This colonial form has persisted in culture for about a decade. The new form has been keyed out using a number of algal taxonomic keys. They key out now as being in the genus Coelosphaerium, which is in a different family from Chlorella.

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Only if you assume that all mutations are negative. For some reason we don't seem able to disabuse you of this notion, no matter how many examples of benefical mutations we show you. Why is that?

Well, of course. But the environment changed, and now we no longer need extra teeth to replace the adult teeth we were expected to lose.Mutations are benefical ultimately only in regards to environment.

Then they weren't, by definition, beneficial. I don't entirely understand how you came to the conclusion that most beneficial mutations are still fatal.The question is, did the mutation allow the organism to leave more viable offspring than the competition (that is, every other conspecific)? If the answer is "yes", the mutation was beneficial, and evolution occurs. Wings don't evolve from nubs, particularly in vertebrates. In vertebrates they evolve from arms. Show me a vertebrate with both arms and wings.I don't know how they evolve in insects, but I could probably find out from one of the books my wife has. How much time do you think it would take, then? Call me strict but I think that's an erroneous use of "beneficial". If it didn't help the organism, then there's no way to say that the mutation was beneficial. Obviously, accidents happen. Not all death is selection - sometimes you get hit by a rock or something.

But that only happens when the organism dies before leaving offspring. So you'll excuse me if I took what you said to mean that even benefical mutations mostly kill the organism, which doesn't make any sense.What did you mean by "lost", otherwise? Where do you think they go?

I actually didn't know that.Interesting. But with so many mutations happening per organism - hundreds, usually - a two percent fixation rate is still a lot. For instance, that's two of your own mutations being fixed in the population.

I think evolution has no problem with "irreducable complexity."Consider that the stone arch, the foundation of cathedral design, is irreducabl complex - remove any one stone and the arch collapses.Yet, arches are constructed one piece at a time. Reflect on how this is done and you will see that irreducably complex systems pose no particular challege to evolution.