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#191
12-08-2006, 05:54 PM
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Re: What prevents evolution?
[ QUOTE ]
In order for A1 and A2 to be mutually infertile (the sense of "speciation" used here), either or both of them must become infertile with A. [/ QUOTE ] This is simply incorrect. Imagine a system in which an egg can combine with a sperm using either of two proteins, P1 and P2, which must match in the egg and sperm. Members of population A have both proteins. This is entirely reasonable, as such a system would confer redundancy to the process. Now population A1 loses the protein P1 to mutation, and population A2 loses the protein P2. Both A1 and A2 can reproduce with A, but not with each other. [ QUOTE ] If you say the propagation of such mutations within the isolated group will preserve its homogeneity, that's fine. However, if a mutation carries with it a tendency to reduce fertility without otherwise improving adaptation (and there's little reason to assume otherwise), merely duplicating the basis of that tendency in a potential reproductive partner does not necessarily correct the problem. In other words, two wrongs don't make a right. [/ QUOTE ] You are making the same error here. The mutations of interest here don't flat out 'reduce fertility'. They reduce fertility WITH RESPECT TO A CREATURE WITH ANOTHER GENOTYPE. As per the detailed mechanism in my earlier post, there will always be a selection for interfertility in a given population. It is the physical separation of A and A1 which allows the mechanisms of fertility to change WITH RESPECT TO EACH OTHER, but NOT within a population group. Language makes an excellent analog for reproductive differentiation. Both English and German share a common linguistic root. No modern english or German speaker is capable of understanding this progenitor language, and neither can they understand each other. That doesn't mean I can't understand an english speaker. Reproduction is not a one way street...it is like communication. Both sexes need to use the same protocol. 
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#192
12-08-2006, 06:42 PM
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Re: What prevents evolution?
[ QUOTE ]
We are not talking about these mutations reducing fertility on its own or as a whole. Mutations cause infertility between the groups because of the effects these changes have on gene alignment etc. [/ QUOTE ] The result is what matters. The specific mechanisms, not nearly as much. [ QUOTE ] Their genomes become incompatible with each other. [/ QUOTE ] Exactly. [ QUOTE ] You can have mutations in a group that increase fertility within that population yet reduce the fertility with the other group. In fact, you would expect this to happen. [/ QUOTE ] Without a specific mechanism stopping it, the opposite is also true. The problem of the intra-species exception is unresolved. You have not accounted for the discrepancy between the respective tendencies within and without species toward reproductive incompatibility. If you think you have done so and I have missed it, perhaps you can reiterate in a concise form.
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#193
12-08-2006, 06:54 PM
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Re: What prevents evolution?
[ QUOTE ]
Without a specific mechanism stopping it, the opposite is also true. The problem of the intra-species exception is unresolved. You have not accounted for the discrepancy between the respective tendencies within and without species toward reproductive incompatibility. If you think you have done so and I have missed it, perhaps you can reiterate in a concise form. [/ QUOTE ] The mechanism that stops it is the need to reproduce with members of one's population, and ONLY that population. Individuals in a population all change; those changes that are compatible with each other are reproduced. That is, it MATTERS that I can mate with somebody who lives next to me. It DOESN'T matter if I can mate with someone in india. Was my prior example unclear? Or are you just focusing on the statements that you find to be most ambiguous?
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#194
12-08-2006, 06:54 PM
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Re: What prevents evolution?
[ QUOTE ]
The result is what matters. The specific mechanisms, not nearly as much. [/ QUOTE ] Um, the result is that they are fertile within the populations but infertile between them. Also, why are you dismissing the mechanism? It's clear that your confusion comes form not understanding the mechanism. [ QUOTE ] [ QUOTE ] Their genomes become incompatible with each other. [/ QUOTE ] Exactly. [/ QUOTE ] Great! We agree! [ QUOTE ] Without a specific mechanism stopping it, the opposite is also true. [/ QUOTE ] Huh? I'm not sure what you are saying here, but if you are saying what I think you are saying then we already explained that they are drifting as a unit so the opposite is not true. [ QUOTE ] You have not accounted for the discrepancy between the respective tendencies within and without species toward reproductive incompatibility. If you think you have done so and I have missed it, perhaps you can reiterate in a concise form. [/ QUOTE ] That's a funny way to ask me to be more concise. What discrepancy are you talking about? In simple terms, please.
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#195
12-08-2006, 07:19 PM
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Re: What prevents evolution?
[ QUOTE ]
[ QUOTE ] In order for A1 and A2 to be mutually infertile (the sense of "speciation" used here), either or both of them must become infertile with A. [/ QUOTE ] This is simply incorrect. Imagine a system in which an egg can combine with a sperm using either of two proteins, P1 and P2, which must match in the egg and sperm. Members of population A have both proteins. This is entirely reasonable, as such a system would confer redundancy to the process. Now population A1 loses the protein P1 to mutation, and population A2 loses the protein P2. Both A1 and A2 can reproduce with A, but not with each other. [/ QUOTE ] That's fair. I suppose I'll have to address A1 versus A2 after all. My mistake, Sephus. [ QUOTE ] [ QUOTE ] If you say the propagation of such mutations within the isolated group will preserve its homogeneity, that's fine. However, if a mutation carries with it a tendency to reduce fertility without otherwise improving adaptation (and there's little reason to assume otherwise), merely duplicating the basis of that tendency in a potential reproductive partner does not necessarily correct the problem. In other words, two wrongs don't make a right. [/ QUOTE ] You are making the same error here. The mutations of interest here don't flat out 'reduce fertility'. [/ QUOTE ] You are the one making the error. It doesn't matter whether this or that PARTICULAR mutation, be it adaptive or otherwise, increases or decreases fertility. The point is that SOME genetic change has to occur somewhere to make offspring A1 diverge in reproductive compatibility with parent A, while the same or similar mutations are somehow not effecting the internal fertility of A1. The emphasis is not on the change A1 undergoes with respect to A, but on the change that does not occur within A1. [ QUOTE ] They reduce fertility WITH RESPECT TO A CREATURE WITH ANOTHER GENOTYPE. As per the detailed mechanism in my earlier post, there will always be a selection for interfertility in a given population. It is the physical separation of A and A1 which allows the mechanisms of fertility to change WITH RESPECT TO EACH OTHER, but NOT within a population group. [/ QUOTE ] That's more of the same omission. See my previous comment. [ QUOTE ] Language makes an excellent analog for reproductive differentiation. Both English and German share a common linguistic root. No modern english or German speaker is capable of understanding this progenitor language, and neither can they understand each other. That doesn't mean I can't understand an english speaker. Reproduction is not a one way street...it is like communication. Both sexes need to use the same protocol. [/ QUOTE ] Languages change due significantly to intelligent design.
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#196
12-08-2006, 07:32 PM
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Re: What prevents evolution?
[ QUOTE ]
[ QUOTE ] Without a specific mechanism stopping it, the opposite is also true. The problem of the intra-species exception is unresolved. You have not accounted for the discrepancy between the respective tendencies within and without species toward reproductive incompatibility. If you think you have done so and I have missed it, perhaps you can reiterate in a concise form. [/ QUOTE ] The mechanism that stops it is the need to reproduce with members of one's population, and ONLY that population. [/ QUOTE ] How do you figure this "need" could prevent mutations of the sort I'm referring to? [ QUOTE ] Individuals in a population all change; those changes that are compatible with each other are reproduced. [/ QUOTE ] Meanwhile, mutations detrimental to fertility accumulate more or less homogeneously within the prospective new species concurrent with its divergence from the original group. [ QUOTE ] Was my prior example unclear? Or are you just focusing on the statements that you find to be most ambiguous? [/ QUOTE ] Your prior examples appear to address what you thought I was going to say rather than what I said.
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#197
12-08-2006, 07:36 PM
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Re: What prevents evolution?
[ QUOTE ]
How do you figure this "need" could prevent mutations of the sort I'm referring to? [/ QUOTE ] C'mon. It doesn't prevent the mutations. [ QUOTE ] Meanwhile, mutations detrimental to fertility accumulate more or less homogeneously within the prospective new species concurrent with its divergence from the original group. [/ QUOTE ] No. Adaptively neutral mutations accumulate homogeneously. Mutations detrimental to fertility are selected against.
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#198
12-08-2006, 07:38 PM
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Re: What prevents evolution?
[ QUOTE ]
[ QUOTE ] [ QUOTE ] In order for A1 and A2 to be mutually infertile (the sense of "speciation" used here), either or both of them must become infertile with A. [/ QUOTE ] This is simply incorrect. Imagine a system in which an egg can combine with a sperm using either of two proteins, P1 and P2, which must match in the egg and sperm. Members of population A have both proteins. This is entirely reasonable, as such a system would confer redundancy to the process. Now population A1 loses the protein P1 to mutation, and population A2 loses the protein P2. Both A1 and A2 can reproduce with A, but not with each other. [/ QUOTE ] That's fair. I suppose I'll have to address A1 versus A2 after all. My mistake, Sephus. [ QUOTE ] [ QUOTE ] If you say the propagation of such mutations within the isolated group will preserve its homogeneity, that's fine. However, if a mutation carries with it a tendency to reduce fertility without otherwise improving adaptation (and there's little reason to assume otherwise), merely duplicating the basis of that tendency in a potential reproductive partner does not necessarily correct the problem. In other words, two wrongs don't make a right. [/ QUOTE ] You are making the same error here. The mutations of interest here don't flat out 'reduce fertility'. [/ QUOTE ] You are the one making the error. It doesn't matter whether this or that PARTICULAR mutation, be it adaptive or otherwise, increases or decreases fertility. The point is that SOME genetic change has to occur somewhere to make offspring A1 diverge in reproductive compatibility with parent A, while the same or similar mutations are somehow not effecting the internal fertility of A1. The emphasis is not on the change A1 undergoes with respect to A, but on the change that does not occur within A1. [ QUOTE ] They reduce fertility WITH RESPECT TO A CREATURE WITH ANOTHER GENOTYPE. As per the detailed mechanism in my earlier post, there will always be a selection for interfertility in a given population. It is the physical separation of A and A1 which allows the mechanisms of fertility to change WITH RESPECT TO EACH OTHER, but NOT within a population group. [/ QUOTE ] That's more of the same omission. See my previous comment. [ QUOTE ] Language makes an excellent analog for reproductive differentiation. Both English and German share a common linguistic root. No modern english or German speaker is capable of understanding this progenitor language, and neither can they understand each other. That doesn't mean I can't understand an english speaker. Reproduction is not a one way street...it is like communication. Both sexes need to use the same protocol. [/ QUOTE ] Languages change due significantly to intelligent design. [/ QUOTE ] But the changes that happen within A1 are distributed among the members of A1. So there isn't any problem. You agree that they are distributed right?
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#199
12-08-2006, 08:18 PM
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Re: What prevents evolution?
[ QUOTE ]
[ QUOTE ] You have not accounted for the discrepancy between the respective tendencies within and without species toward reproductive incompatibility. If you think you have done so and I have missed it, perhaps you can reiterate in a concise form. [/ QUOTE ] That's a funny way to ask me to be more concise. What discrepancy are you talking about? In simple terms, please. [/ QUOTE ] Funny? Whatever amuses you. The discrepancy is between two drifts: 1) between parent A and offspring A1 and 2) internal to A1. What do you suppose causes it (this discrepancy)? The fact that mutations tending to decrease reproductive compatibility with A propagate throughout A1 in its isolation doesn't get you anywhere. Such mutations wouldn't necessarily correlate any better with other members of A1. Also, the same reproductive defect in both prospective mates does not cancel itself out. From your next post: [ QUOTE ] Mutations detrimental to fertility are selected against. [/ QUOTE ] Yes, by extinction. (I still can't help thinking you're being deliberately obtuse.) Vhawk01, [ QUOTE ] But the changes that happen within A1 are distributed among the members of A1. So there isn't any problem. You agree that they are distributed right? [/ QUOTE ] The changes are distributed and cause an increasing accumulation of incompatibly that must, all else being equal, eventually lead to the extinction of A1. There exists no observed feedback mechanism to maintain the internal fertility of an isolated group against succumbing to the same drift that differentiates it from the progenitor. Selection is much less efficient a process than extinction, considering which side of the equation random change is on.
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#200
12-08-2006, 08:37 PM
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Re: What prevents evolution?
You keep saying 'incompatibility' like there is some trait, incompatibility (In) the increase of which makes you more likely to go extinct. This is definitely wrong. Humans have BOATLOADS of In, since we can't mate with any other species save one (probably). Its just a term used to descrbie relative incompatibility between different groups. So, having a whole lot of In doesn't hurt you at all.
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