Evolution Requires Reduction in Genetic Diversity

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Sorry, I've made my case that they are essentially the same in their operations and effects and that's all there is to say in the teeth of your incomprehension.

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The only thing we don't understand is why you expect us to agree with you when you are obviously wrong.

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Most discussions of genetic drift assume this sort of intrapopulation isolation is possible and occurs. It's strictly the result in that case of random selection of mates, without any particular explanation.

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No. They do not. They assume that reproductive isolation is possible but not that drift will cause it within a breeding population as you claim. If you want to assert otherwise, then give an example. Not a link to a Google search (a tactic which seems designed to obfuscate the issue) but a link to an actual mainstream discussion of genetic drift that actually supports the idea.

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BUT AFTER WRITING MOST OF THIS POST I REALIZED YOU AND PAULK MUST BE THINKING OF SOME KIND OF PHYSICAL ISOLATION SUCH AS GEOGRAPHIC ISOLATION, BUT I'M TALKING ABOUT REPRODUCTIVE ISOLATION. So I went back through the post and noted that where it seemed to be appropriate.

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That is not a realisation, it is a fantasy as is quite obvious. Asking after the cause of the isolation is not assuming a particular cause. And in the quote immediately following Percy makes it clear that he is not considering geographic isolation - he is asking about co-resident populations.

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So the upshot is that a subpopulation is being created of the favored alleles any way you look at it, the subpopulation of favored traits/alleles growing in number within the overall population, the unadapted traits/alleles diminishing in number.

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What's interesting is that this "upshot" is what I expect to happen - as I said. Agreeing with me - and omitting the point of disagreement - hardly demonstrates that I am wrong.And, as I pointed out while you can identify a subpopulation in the case of selection you can't even do that in the case of drift.

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Funny then that descriptions of genetic drift imply the development of a new subpopulation by random selection, meaning a collection of traits that sets it apart from the main population.

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The only funny thing about it is that you think that it supports your position. The fact that drift will cause reproductively isolated populations to diverge does not mean that drift will cause reproductive isolation within an interbreeding population.Again, if you disagree show us an actual discussion which says that drift is expected to produce reproductive isolation within a breeding population.

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Remember we're talking about REPRODUCTIVE ISOLATION, not geographic isolation or any other kind of isolation. Sexual selection can isolate individuals and create a subpopulation within a population. In fact the more I think about it the more it seems this must be how such an adaptive subpopulation would form.

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Again, we are not disputing that there are circumstances where you could get reproductive isolation within a breeding population. We're arguIng that that is not the normal or expected consequence of selection or drift. it needs particular circumstances, which are not going to be that common.

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PaulK brought up the subject of genetic drift and natural selection and I gave my view of it in response, I have no other reason to continue it. I haven't changed my view, I've had it for years so I'm not going to drop it beyond not pursuing it after this post unless somebody else keeps it alive.

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In fact I was responding to your claim that population genetics "doesn't do that". And if you can't see that selection and drift are the major mechanisms of change within population genetics then that is your problem. So, strictly speaking, you brought it up - I was pointing out your errors.And I have to say that I don't expect you to start caring about the truth any time soon. a pity. You aren't stupid. But you waste your intelligence by not bothering to employ it to understand what you are talking about or to produce good arguments.

What you're talking about actually has a name: sympatric speciation. The link is to the Widipedia article. If you read it you'll find that plausible mechanisms remain elusive, and that it is not a common consequence of genetic drift and natural selection (you've been arguing the opposite and are clearly wrong). According to Wikipedia:

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In multicellular eukaryotic organisms, sympatric speciation is thought to be an uncommon but plausible process by which genetic divergence (through reproductive isolation) of various populations from a single parent species and inhabiting the same geographic region leads to the creation of new species.

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If you believe this form of speciation is necessary to arguing your position then please explain how. Otherwise please drop it.

They are only "essentially the same" if you ignore the differences. (where have I seen this before ... ?) All evolution is "active" whether it is "clearly happening" or not. Evolution to maintain stassis is a very active form of evolution to maintain the level of fitness in a stable environment that has developed over many generations. Gene flow is also evidence of active evolution.Every time there are offspring there is evolution actively adding mutations to the population genome.Every time there is mating there is evolution actively selecting the phenotypes that are successful surviving to breed, actively modifying the phenome of the population to fit the ecology.When you say that the effects of natural selection, population splits and genetic drift are the same you are just plain wrong.Natural selection actively sorts the population for phenotypes that survive to breed successfully in every generation.Population splits may divide the population evenly or not evenly, it may result in some differences in allele frequencies and it may not. The split may occur because some phenotypes have evolved a trait beneficial in a different ecology that they can now use, but the parent population is not well suited for (black pocket mice), but that is a form of natural selection taking advantage of opportunities.Genetic drift occurs to breeding populations, and it happens when traits are eliminated from the population with no selection of the individuals for fitness to the ecology. It can even eliminate beneficial traits. Except when it doesn't, as you have often been told. The new adaptations that do occur would be due to mutation and selection in a different ecology with different selection pressure. Except the evidence shows that you are wrong. A change in beak size was (gosh) actually observed by Peter and Rosemary Grant in response to climate change on one island -- it got dryer, seeds got harder, beaks became bigger, it got wetter, seeds got softer, beaks became smaller.So I suppose you will argue that the beak size change came first and that this caused the climate changes to accommodate the new beaks?In some cases pre-adaptation can occur, such as the black pocket mice, when individuals benefit from a new trait that allows them to survive and breed in a new ecology, but is by no means the normal path of evolution.It is pointless discussing your fantasy further because it is based on false perceptions like these. Fix the errors first then we can look at the rest.You can't pretend that the situations of a founding event apply to all breeding population with nothing but your biased\underinformed imagination. It isn't a new paradigm fighting for acceptance because you don't have evidence for it and ignore evidence contrary to it.Enjoy.Edited by RAZD, : clrtyEdited by RAZD, : mo

It's not speciation until it leads to speciation and that has not been part of my argument. And I'm very familiar with that Wikipedia article. I think it's about time to leave. We'll see.

The effects, as I clearly described them, are the same in all three cases.'Bye.

You said it would lead to a subpopulation that was reproductively isolated from the parent population though co-located with it. Inability of a subpopulation to interbreed with the parent population is part of the definition of speciation for sexual species, so you're still trying to redefine speciation. I've already ruled against inventing new definitions for existing terminology.Responding to your next message: This is a bald declaration without any support, while the rebuttals clearly explained why you were wrong. I asked you to stop threatening to leave, yet you have kept doing it, though veiling it somewhat. The reason you shouldn't do this is because it brings discussion to a halt, and then you don't leave, causing a fitful and disconnected restart of the discussion. I will shortly be suspending your right to post in this thread.

Let me fix that for you: As has been clearly documented ... Take your time off to review the evidence and the facts around it.Enjoy

These are the kind of arguments you might expect when belief dominates evidence.That's why, with hard core creationists, it is a waste of time explaining evidence, scientific method, theory and all the rest. It is water off the duck's back. It just has no effect. RADZ has explained a number of things in great detail, all of which did no good, except hopefully helped educate some lurkers.Hard core creationists, on the other hand, will ignore, obfuscate, twist, misrepresent and otherwise abuse the evidence so that it conforms to their beliefs, and then claim that they are doing science. "We use the same facts, just different interpretations" and "Its just a theory" are two of the nonsense phrases we sometimes hear.What a waste of my time, that could have been spent on more productive things, like dusting my dental floss collection.

Indeed. But a simple test of the claim is that if the three systems are "essentially the same" then why are there three systems defined and described instead of one.Enjoy

There you go, using evidence again.You know that's not going to work. Surely you've learned that by now!

Yep thet evi-dunce is the work of the devil Ya can't fool a TVUE believer Don't call me Shirley

I was wrong. Bad stuff deletedEdited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.Edited by NoNukes, : No reason given.

Isn't this the more normal case? Species really are not homogeneous, so at any time there are always variants. A change in ecology can produce new natural selection winners and losers. Doesn't that explain at least some of the correlation between birds with big beaks and the appearance of tough nuts to crack?

The key to pre-adaptation is that it occurs before the ecological change that makes it beneficial -- black mice, black pepper moths, etc -- so that selection just shifts the frequencies of alleles in the populations towards the beneficial traits and away from the least beneficial traits.Post-adaptation would be the additional changes that continue the adaptation process beyond what was available in the initial population.Do the largest beaks in the population survive and breed more than other sizes, and then does the following generations have even larger beaks that improve survival and breeding -- does the trait distribution move outside the original distribution.Again we can look at Pelycodus:

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Evolution of Pelycodus
an early Eocene Primate from Big Horn Basin, Wyoming

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The chart documents the evolution of the Eocene lemur-like primate Pelycodus into Notharctus. The horizontal scale is an index of molar tooth size. Each horizontal bar gives the mean (vertical bar), two standard deviations (thick horizontal bar) and range (thin horizontal bar) for the indicated number of skulls from a series of fossil deposits. The index increase from 1.0 to 1.4 is an approximate doubling in size. The inset photograph shows a reconstruction of Notharctus venticolis, the species in the upper right of the series. [diagram after Gingerich]

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Each layer shows the population distribution of sizes and the trend is for larger and larger individuals until with P.Jarrovii ALL the individuals are larger than the original P.ralstoni individuals ... this adaptation is the rule imho, although you could argue that each layer had members that were pre-adapted to be selected for their larger size, that is really just the natural selection of the available variations, and it is the long term trend that is the overall evolution.In my opinion.Enjoy.