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Author | Topic: The End of Evolution By Means of Natural Selection | |||||||||||||||||||||||||||||||||||||||||||||||||
Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
Hello bluejay, thanks for the nice welcome.
Natural selection does not have to smite all the competitors, it just has to smite some of the competitors. I have been giving oversimplified examples trying to make my point but then you all come back with the subtleties and exceptions and so on. I'm trying to talk about a trend that I think is observable if one focuses on it. When you say NS just has to smite SOME of the competition, fine, I don't want to argue about HOW MUCH of the competition has to be smitten, I just want to focus on the fact that SOME get smitten! That NS smites! It smites the competition. That's its JOB as it were. It gets drastic only at the extremes, fine, like when a snake eats up all the nonpoisonous newts in a population and the poisonous ones then multiply. They probably still have the alleles for the nonpoisonous type among them too as this isn't yet speciation, but those alleles have been "smitten" in the sense that they can't express their phenotype, right? How, I don't know, something to do with dominance and recessiveness? If the poisonous newt continues to be selected eventually it could become a species and then the alleles for the other type will finally have disappeared, no? All I meant by getting a trait "established" was that ... OK I'm thinking of a ring species. The salamanders in California that ring a desert area. Each population has a different "look" to it than each other population, its own peculiar look that identifies it. Maybe I don't have this quite right but I assume that to get this look peculiar to its population required the blending of its own collection of alleles for various traits which occur in different frequencies among them than in the original population. The original founders of the new population would have looked like the population from which they came, but due to their smaller numbers, their different proportions of alleles, perhaps even the absence of some alleles altogether, they mixed together through generations in the new setting to produce this new phenotype, this new look, this new color pattern that distinguishes them from the first population. This is what I think of as "established" -- when the whole population has this new characteristic. They had to have time for their genetics to blend together into a new phenotype characteristic of their new population. Is this what "fixed" means? They don't HAVE to completely lose alleles for this to happen, merely have them in new frequencies, but the TREND down the series of populations IS toward the loss of alleles simply because each new population starts from a small number relative to its parent population. Edited by Faith, : No reason given. Edited by Faith, : grammar Edited by Faith, : bolding
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
PaulK:
I don't know if increased variation in mitochondrial DNA and hypervariable minisatellite loci contribute to the genetic diversity needed by the cheetah to recover or not. It isn't the normal expected source of genetic diversity so you'd have to tell me what it means.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
Phage, I still struggle to get what you are talking about, and on top of that it looks like I didn't express myself very clearly either. If I can I'll come back to your post later.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
Am I missing something here, or is the essence of Faith's problem that in her attempt to cull one allele out of the herd she is forgetting that each generation of an organism has numerous mutations? While a population might be fixing the allele for a particular trait, and thus reducing the genetic variability in that population vis a vis that one trait, there are at the same time new alleles and new traits evolving which open up the potential for variation, selection, drift, and so on, regarding completely different aspects of the fitness of individuals in the population. I'm trying to demonstrate what the selective/isolating processes that lead to speciation do -- they reduce genetic diversity which allows a new phenotype to become characteristic of a new subpopulation. Plenty of other things are also going on that may change that direction but the isolating-selecting processes always work in the direction of reducing genetic diversity. If all kinds of mutations and new traits are accumulating you aren't going to get to an actual new species while that is going on.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
The scientific evidence suggests a pattern of one tree (or bush), branching all the time, while the biblical concept of "kinds" requires a forest -- that is, each of the "kinds" is specially created and does not branch. I suspect this is the root of this entire thread. The kinds do branch, they evolve. Some creationists do have a wrong idea of fixed kinds but that's really a very old idea and it's very clear that they evolve into many different varieties. This should have been known to creationists all along too because domestic breeding is an ancient art.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
That is, if you want to maximize certain characteristics of your dog, what you have to do is make sure it can't breed with dogs that have different characteristics. It's a process of eliminating what you don't want. * sigh * But this process may reduce the diversity in each breed of dog but increases the number of breeds of dog, thus producing a net increase in diversity. The net result is that breeding by humans has quite visibly and obviously increased the diversity of the dog/wolf species. This isn't GENETIC diversity you're talking about. You're talking about the proliferation of varieties or breeds. Lots and lots of those, yes. But EACH of the breeds has been able to form BECAUSE it has its own reduced complement of alleles compared to the parent population. Edited by Faith, : typo
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
You must remember that your whole argument is based on assuming that the supply of new variation must be inadequate. This is a complete misreading of what I'm doing and I'm at a loss how to correct it since it keeps cropping up. I am NOT "assuming" this at all, and my argument is not "based on" it. It is an OBSERVATION that the selecting-isolating factors determine the phenotype of a new subpopulation by reducing its genetic diversity. The variation that everybody is talking about comes in at a different point in the life of the species. Oh I can't get this said in any way that you aren't going to continue to object to in the same old way so I have to find new waysto say it. The variation you keep wanting me to take into account simply does not enter into what I'm trying to get said. So go ahead and assert that I'm ignoring addition and I'll just grind my teeth again. Edited by Faith, : correct run on sentence
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
But Percy, her argument isn't even consistent with her religious views. Even if the animals on the ark were modern species rather than the "kinds" preferred by most YECs, every species would have suffered a bottleneck. And according to Faith's argument they cannot recover from that. YECs need a mechanism to generate variation even more than evolution does to explain why we don't see evidence of that bottleneck. This point was brought up in the original discussion so Faith has no excuse for ignoring it. I don't really think in terms of recovery, because bottleneck is just one way I see new species forming. I realize that at the level of genetic depletion we see in some species today, in this fallen world it's a hazardous condition to be in but I don't even think about the cheetah as some sort of deficient animal. I think of it as an elegant creature unfortunately born into a fallen world. The overhunted seals are thriving in great numbers despite their genetic depletion. Genetic depletion is a problem in this fallen world as it would not have been in the original created world, but even here animals in that state can sometimes do just fine. The process of genetic reduction is a way for wonderful new varieties to emerge, it's a very creative process, it is only unfortuantely deleterious in this death-ridden world. I assume enormous genetic diversity in the passengers on the ark, that has since played out in the many splittings and variations and speciations we see today. There would be no end to them if death had never entered the world. =========================================I hope I will be forgiven for bringing any of my Bible-based beliefs onto a science thread, but clearly I'm simply responding to others who have brought up the subject and it may clarify some issues people have with my argument here. If anyone wants to pursue the topics raised it should be on another thread. Edited by Faith, : to add last paragraph Edited by Faith, : No reason given.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
This isn't the way it works. For Darwin's 15 different tanager species there were not 15 different alleles for the shape of beaks, one for each species. Bird beaks are controlled by the expression of the Bmp4 gene. All the different beak shapes are the result of different timing and spatial controls on the expression of the Bmp4 gene. Expression of the Bmp4 gene is under the control of regulator genes with names like Shh and Fgf8. In other words, beak shape is under the control of more than one gene and more than one type of gene, and bird gene pools of any species possess a great deal of variation. This is why beak expression is so plastic under the influence of changing environmental pressures. So natural selection doesn't enter into it with the finches? Or they aren't true species and could revert at any time?
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
My understanding of speciation is that, just as with domestic selection, the selected trait is isolated from other alleles for that trait so that it can disperse through the new population down the generations and thus come to characterize the new species. If the alleles for different kinds of beaks were not eliminated you would not have this new species. * sighs again * In the case that you bring up, the action of evolution may well have diminished the variation within species, but it also produced more species. Thus increasing genetic diversity. Dear dear Dr. A. Yes I got annoyed at some way you expressed something and I apologize. I am now finally getting to your posts and it seems to me you are missing my point. My focus iIS on the individual evolving population, not the whole gene pool. I'm interested in how a subpopulation gets characterized by one single beak type -- because this is evolution is it not? -- and on the model of domestic selection I figured it could only occur if other beak types were eliminated from the population's own gene pool. Now Percy tells me beaks don't get selected like that but I'm sure there are plenty of other examples where what I'm describing is closer to what happens.
The interesting thing about what you're doing is that you appear to be committing the fallacy known as "moving the goalposts" inside your head, but without ever doing so explicitly. In your line of argument, as soon as radiative adaptation starts happening, you move the goalposts and it becomes two separate examples of evolution, both of which are conservative. I have no idea what you are talking about. I suppose I'm simply not doing a good enough job of making myself clear but believe me what I've been saying from the beginning is what I'm still trying to say. I'm also trying to learn from people's objections which I hope might improve my terminology and refine my argument but otherwise, no, same argument.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
If you want to talk about what I believe about the ark please start another thread. I promised Percy I would not talk about Biblical subjects on a science thread.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
It seems to be generally overlooked that for evolution to occur, alleles must be eliminated, thus reducing genetic diversity. Not overlooked, simply not true. Evolution can very readily occur without any alleles being eliminated. Yes, I do keep forgetting the example of a selected allele working its way through a population generation by generation, and in that case you get the new trait without the loss of genetic diversity. Usually I'm thinking of the cases where a subpopulation of reduced numbers is created, which does eliminate alleles, does create a new population with its own identifying characteristics, and can lead to speciation.
But I realize this has to be demonstrated. Having said this you then go on to do nothing of the sort. The fact that genetic drift and selection can both lead to the fixation of an allele within a population in no way means that they must or that this forms an 'inexorable' trend. I'm thinking of the situation of reproductive isolation of a smaller number from a larger population, which is a main way new varieties develop, and even speciation. The process by which an allele becomes fixated seems to demonstrate the case I have in mind; it doesn't matter if it doesn't always happen that way, when it does it demonstrates what I'm trying to talk about -- if an allele DOES become fixated it happens according to the processes I'm describing does it not? Ring species keep coming to mind because they continue to form whole populations with strikingly unique characteristics by migration of small numbers from larger populations, a trend that has to involve progressively reducing genetic diversity from population to population as the new unique populations develop.
You have no evidence, you have no demonstration, all you have is your totally uninformed assumption about what happens, one that is plainly contradicted by the evidence. OK, if you say so.
There is no way to get a trait established in a population if alleles in competition with the allele for that trait are not eliminated. Not true, to be 'established' a trait just needs a sufficient frequency that it will not be readily eliminated from the population by the vicisitudes of genetic drift. Other alleles absolutely do not have to be eliminated for this to happen, although obviously their relative frequencies will change somewhat. I'm trying to talk about a trait that comes to represent an entire population, not just a trait that gets itself established as a variation within a population. I'm trying to talk about the evolution of whole populations, down to speciation.
I've always liked the cheetah example because it is a case of a wonderfully selected animal that demonstrates extreme genetic reduction, to the point of fixed loci for many traits. As others have pointed out that is just flat out fantasy, cheetahs aren't an example of extreme genetic reduction due to being 'wonderfully selected' but due to a severe population bottleneck back in their evolutionary history. A bottleneck IS extreme genetic reduction. Which brought out a really great animal.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
Dr Adequate raised a very relevant question about your claim that two individuals of a species possess a great deal of variation. The reality is that variation in a sexual species can not get any less than two individuals. One non-pregnant individual doesn't count since in a sexual species that means the species is effectively extinct. I'm not a uniformitarian. I believe things were very different 4500 years ago genetically speaking. And even MORE different before the Flood. When I'm talking about today's situation I don't bring that up. He brought it up. It's based on the Bible. It doesn't belong here. Edited by Faith, : No reason given.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
I don't KNOW what people wrote two days ago. I don't have your perspicacity in knowing what's relevant and what isn't. And you can spare the insults if you want this thread to continue at all. Of course maybe you don't.
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Faith  Suspended Member (Idle past 1474 days) Posts: 35298 From: Nevada, USA Joined: |
Can we please agree on a few things. Or not. Simple stuff.
1) In domestic breeding -- let's stick to dogs -- do you agree that you get and maintain a breed by being sure you breed it with its own type? 2) Do you agree that this is to protect the breed's particular allele complement from contamination from alleles of other dog types? 3) Do you agree that any dog breed possesses a very limited genetic diversity with respect to the total dog population? 4) Do you agree that it is its limited genetic diversity that is the basis for the characteristics of the breed itself and that if there is any increase in the genetic diversity the breed will lose its character at least to some extent? 5) Do you agree that Darwin based his natural selection on domestic selection? 6) Do you agree that natural selection is the "engine of evolution?" 7) Do you agree that the end goal of evolution is speciation or is evolution simply any change at all whether it ever leads to speciation or not? Edited by Faith, : added two questions Edited by Faith, : to add numbers for future reference if needed
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