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Author | Topic: The End of Evolution By Means of Natural Selection | |||||||||||||||||||||||
Faith  Suspended Member (Idle past 1472 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 1472 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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Dr Adequate Member (Idle past 312 days) Posts: 16113 Joined: |
I assume enormous genetic diversity in the passengers on the ark ... You do? The animals went in two by two, hurrah, hurrah. Do you suppose that the two wolves contained within themselves sufficient genetic diversity to produce every breed of dog --- so that when they bred, sexual recombination might have at once produced a litter consisting of a greyhound, a chihuahua, a bulldog, a poodle, a Pomerian, and an Old English Sheepdog?
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Faith  Suspended Member (Idle past 1472 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 1472 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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PaulK Member Posts: 17827 Joined: Member Rating: 2.3 |
Bottlenecks and reduced genetic diversity are a major part of this topic. So that fact that your beliefs include major bottlenecks in many species, a belief contradicted by the existing genetic diversity - and if your arguments only make this problem worse for you it seems to be clearly relevant. Even if it merely highlights a major inconsistency in your own beliefs, it shows that you have not clearly thought things through since the previous thread, even though the issue was one that had been raised. And if you have not managed that then I suggest that a little less certainty on your own part might be appropriate. Other Bible-based beliefs can be discussed elsewhere.
quote: Neither the severe bottleneck in the cheetah's past, nor the bottlenecks that would afflict the species in the Ark - if the story were true - are examples of speciation. And, as I pointed out, the typical YEC view involves multiple speciation events after the Flood to produce a wide array of modern species from a single "kind". We do not find evidence of the many severe recent bottlenecks implied by the Flood story - and both your ideas and the common YEC idea of ancestral "kinds" occupying the Ark only make the situation worse. Unless you abandon the Flood story altogether you need to explain why genetic diversity is far HIGHER than it should be in every species that should be affected.
quote: You cannot have "enoromous genetic diversity" in a single pair. You can only have a maximum of 4 alleles for each gene. That is quite basic genetics.
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Percy Member Posts: 22502 From: New Hampshire Joined: Member Rating: 4.9 |
Hi Faith,
Discussion has moved on from what people wrote two days ago. If you truly want clarity to emerge then my advice is to respond to all the relevant points made, not to all the messages posted. Switching your responses back and forth between current and old posts is fragmenting your thread and causing it to lose continuity. Tanypteryx in Message 93 and Dr Adequate in Message 96 both posted excellent explanations just last night that were right on target for where the discussion was at that time. The best thing you could do is respond to them. Stop worrying about responding to everybody. As Emerson said, "A foolish consistency is the hobgoblin of little minds." --Percy
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Dr Adequate Member (Idle past 312 days) Posts: 16113 Joined: |
It is an OBSERVATION that the selecting-isolating factors determine the phenotype of a new subpopulation by reducing its genetic diversity. Sure, when a subpopulation is formed, for example by a flock of birds getting blown to a vacant island, this produces a genetic bottleneck.
The variation that everybody is talking about comes in at a different point in the life of the species. Yes. So? It's as though you explained to us that parachuting must be fatal because just after someone jumps out of a plane, they accelerate to a breakneck speed. We point out that after you pull the ripcord, the parachute opens, slowing you down. "Ah," you reply, "but that comes at a later stage of parachuting. Why does everyone want to talk about what happens after the parachute opens, when I've made it clear that my focus is on what happens before the parachute opens?" Well, because what happens afterwards vitiates your argument. You don't get to pick and choose one aspect of the process to look at and ignore the rest, if you wish to offer a critique of the whole process. Edited by Dr Adequate, : No reason given.
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Percy Member Posts: 22502 From: New Hampshire Joined: Member Rating: 4.9 |
Faith writes: 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. 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. --Percy
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Faith  Suspended Member (Idle past 1472 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 1472 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 1472 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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Percy Member Posts: 22502 From: New Hampshire Joined: Member Rating: 4.9 |
Hi Faith,
There were no insults in my Message 112, just advice. I'm sure I'm not alone in finding the discontinuity unpleasant and a barrier to clarity. I again suggest you focus on the current discussion by responding to Message 93 and Message 96. --Percy
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Percy Member Posts: 22502 From: New Hampshire Joined: Member Rating: 4.9 |
Hi Faith,
As long as you understand that two individuals represent the least variation possible in a sexual species then there's no need to respond. But it does raise the question that if you believe that giraffes today have many fewer alleles now than giraffes thousands of years ago, and if you also believe that reducing variation is how speciation happens, then how could giraffes today with their greatly reduced genomes be the same species as giraffes then? --Percy
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PaulK Member Posts: 17827 Joined: Member Rating: 2.3 |
quote: Since your argument asserts that evolution will end, and since it will not end if diversity is replenished I cannot see why you call it a "complete misreading". Even if we assume that your "OBSERVATION" is completely and entirely true it cannot stand alone as an argument against evolution.
quote: Here's how you could say it so that everybody will get the point. "I was wrong. Evolution will not end. The supply of new variation means that evolution can continue indefinitely."
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