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Author Topic:   Evolution Requires Reduction in Genetic Diversity
Taq
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Message 42 of 1034 (691791)
02-25-2013 12:44 PM
Reply to: Message 30 by Faith
02-25-2013 3:49 AM


Re: The effect of the flood bottleneck
Sure you may have mutation-created alleles in the new mix (if anything other than damage actually occurs by mutation, which again of course I don't believe), but even if you do they are still going to have to either become part of the new phenotype while the gene pool as a whole loses genetic diversity, or they will themselves have been eliminated in the population split.
Mutation doesn't stop after a selection event. It is going non-stop in every single generation. Each time a new individual is born in the population you get an increase in the genetic diversity of the population because that individual will be born with a genome sequence that has never existed before in the entire history of that lineage.
You might as well be arguing that rivers should run dry in a year's time because rivers only flow downhill, they can't flow uphill to replenish the water flowing downhill. Just as rain replenishes the water needed to flow downhill. so too does mutation produce the new genetic diversity that flows through selection.

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 43 of 1034 (691792)
02-25-2013 12:47 PM
Reply to: Message 36 by Faith
02-25-2013 9:19 AM


Re: Evolution requires increases and decreases in Genetic Diversity
The alleles that bring about the different beak, if isolated and selected to characterize a new subpopulation ...
Prior to that point, you had an increase in the genetic and phenotypic variation within the species.
You do not get new features characterizing a whole population or "species" or "subspecies" without eliminating all the competitors.
So at one time you had the A allele. A mutation produces the B allele. The B allele becomes more common to the point that 50% of the population has allele A and 50% has allele B. So you started with just allelel A, and then you had A and B. That is an increase in genetic diversity.

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Taq
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Message 44 of 1034 (691795)
02-25-2013 12:58 PM
Reply to: Message 34 by Faith
02-25-2013 8:41 AM


Re: mutations
When I'm talking about the reduction of genetic diversity I'm talking about the situation where "evolution" is actively occurring, where a reduced number is reproductively isolated and inbreeds for some number of generations to produce its own characteristics as a population.
New mutations occur in reproductively isolated and inbreeding populations as well.
When you get out to "speciation" or the actual loss of ability to interbreed with former populations THEN you can talk genetic impoverishment and that IS the natural ultimate ending point of these processes if they continue that far.
New mutations will occur in each of these new species which will increase the total genetic diversity of the clade given that these mutations will not be lineage specific due to different selective pressures.

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Taq
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Posts: 10195
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Member Rating: 3.2


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Message 52 of 1034 (691807)
02-25-2013 1:29 PM
Reply to: Message 47 by Faith
02-25-2013 1:09 PM


Re: mutations
So what?
This means that genetic diversity starts to increase after a strong selection event.

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


Message 53 of 1034 (691809)
02-25-2013 1:36 PM
Reply to: Message 45 by Faith
02-25-2013 1:06 PM


Re: Ring Species -- Greenish Warbler -- and Genetic Diversity
I'm talking about how diversity is REDUCED (sometimes eliminated but ALWAYS reduced) by the fact that alleles that don't contribute to the new phenotype simply are not present in that gene pool or the phenotype would not develop.
How do you get a new phenotype other than through an increase in genetic diversity? How do you get competition between alleles without the production of new alleles which is an increase in genetic diversity?
If we start with 100% allele A and later end up with 50% allele A and 50% allele B, would you count this as an increase in genetic diversity?

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 Message 57 by Faith, posted 02-25-2013 2:20 PM Taq has replied

  
Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


Message 56 of 1034 (691812)
02-25-2013 2:01 PM
Reply to: Message 55 by Faith
02-25-2013 1:56 PM


Re: Ring Species -- Greenish Warbler -- and Genetic Diversity
The idea is that the other beak is in the gene pool but less and less expressed as the chosen beak dominates
If it can be shown that the other beak comes about due to a new mutation, would you count this as an increase in genetic diversity?

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


Message 60 of 1034 (691817)
02-25-2013 2:31 PM
Reply to: Message 58 by Faith
02-25-2013 2:23 PM


Re: Ring Species -- Greenish Warbler -- and Genetic Diversity
If it does, it's replacing another allele for beak type anyway you know, and surely all the possible beak types are already present in the gene pool so this "increase in diversity" is redundant and as I keep pointing out, once it gets selected the genetic diversity starts getting reduced anyway so it really amounts to nothing new in the end.
Once it appears, the genetic diversity has increased, has it not?
It would seem to me that you have competing mechanisms: one that increases genetic diversity and one that decreases genetic diversity.

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 Message 58 by Faith, posted 02-25-2013 2:23 PM Faith has replied

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 63 of 1034 (691821)
02-25-2013 2:40 PM
Reply to: Message 57 by Faith
02-25-2013 2:20 PM


Re: Ring Species -- Greenish Warbler -- and Genetic Diversity
The gene pool contains all the alleles for all the variations, no increase is needed.
Of course, since that is the definition of gene pool. What you are ignoring is that each generation adds new mutations to the gene pool, mutations that didn't exist in the previous generations.
If you want to think they were created by mutations, I'll tolerate that idea up to a point, but it would be silly to think a brand new mutation is always going to be selected as the basis of a new phenotype when the gene pool is full of alleles for all kinds of variations anyway.
It is equally silly to think that no mutation can lead to a change in phenotype. The genetic differences between humans and chimps explain the morphological and physiological differences between humans and chimps. Quite obviously, mutations can change phenotype.
When a new smaller population splits off the idea is that it contains a different mix of alleles than the mother population had and those that dominate in the new will be different than those in the old and that's what brings about a new phenotype.
It also contains population specific mutations that accumulate after the two populations separate. This is an increase in genetic diversity.
The alleles already exist, Taq, whether they were created by mutation or built in at the beginning.
The alleles did not exist prior to the mutation.
Why are you guys always assuming you need new ones?
Go to my thread on antibiotic resistance and I will show you. We have also discussed the evidence for the mutations leading to the dark fur allele in pocket mice.
If you're right and mutation is the source of alleles, then I guess you'll get some new ones but there's no guarantee the newer mutations will be selected anyway, why should they be?
If the mutation leads to a beneficial adaptation, why shouldn't it be selected for? For example, a mutation that produces darker fur that offers superior camouflage in dark lava fields.
Sure. But I have no doubt there are already Bs and Cs and all the rest in the gene pool to begin with.
What is your evidence for this?

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 65 of 1034 (691823)
02-25-2013 2:44 PM
Reply to: Message 62 by Faith
02-25-2013 2:39 PM


Re: The effect of the flood bottleneck
The variation is BUILT IN to the genome it does not need to be ADDED.
Then why did mutations have to occur in the mc1r gene in pocket mice in order to get mice with dark fur?
Just a moment...
They clearly show evidence that the dark allele was not part of the ancestral gene pool, and that the mutations appeared after the dark lava fields appeared. This is based both on selection pressures on the dark allele and on sequence variation of the m1cr alleles. You had an ancestral gene pool without the dark allele. You then had volacanic eruptions producing fields of dark lava. You then had the appearance of mutations that produced dark fur. These mutations were then selected for in populations living on the black lava.
Edited by Taq, : No reason given.

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 Message 71 by Faith, posted 02-25-2013 3:11 PM Taq has replied

  
Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


(1)
Message 70 of 1034 (691829)
02-25-2013 2:58 PM
Reply to: Message 67 by Dr Adequate
02-25-2013 2:50 PM


Re: The effect of the flood bottleneck
This conflicts with our actual observations; for example observations of clonal lines of haploid species.
Not to mention the observations of diploid species like humans. On the disease side, we see children with genetic diseases that are caused by mutations. These diseases were not found in either parent.
Even more, scientists have sequenced the entire genomes of families to measure the actual rate of mutation in humans.
http://www.nature.com/...f/ng.862.pdf%3FWT.ec_id%3DNG-201107
And, as you mention, studies in haploid species does shed light on the issue which is why I would like to see Faith participate in this thread:
EvC Forum: Application of the Scientific Method: Antibiotic Resistance

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


Message 74 of 1034 (691834)
02-25-2013 3:24 PM
Reply to: Message 72 by Faith
02-25-2013 3:15 PM


Re: The effect of the flood bottleneck
But surely you know we have no problem with mutations causing DISEASES, Taq.
Mutations that cause disease are still an increase in genetic diversity.
It's the idea that they ever do anything beneficial that's at issue.
That issue has already been settled. The pocket mouse example is just one of many.

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 78 of 1034 (691840)
02-25-2013 3:36 PM
Reply to: Message 71 by Faith
02-25-2013 3:11 PM


Re: The effect of the flood bottleneck
What IS the evidence for that? I cant read the whole article right now but skimmed the first part and don't see how it's so certain that a mutation was involved.
1. Selection pressure. They surveyed many regions across the desert spanning Arizona and New Mexico. This survey included two black lava fields (one in Arizona and one in New Mexico) separated by 750 km, the areas immediatly around each lava field, and the desert between the two lava fields. What they found is that in between the lava fields there were no black mice. Even more, there were no alleles associated with dark fur even though light fur is the recessive allele (it only takes one dark allele to have dark fur). On the lava fields, the vast majority of mice had dark fur, and the dark allele was very, very common. In the areas directly around the dark lava fields there was a mixture of the two phenotypes. Right away, one thing is very appararent. There is extremely strong negative selection against the dark allele in the light colored desert that separates the two lava fields. If the dark allele had emerged in the light colored desert it would have disappeared in just a few generations. The only way that the allele could survive is if the mice carrying the mutation moved into the black lava fields.
2. Variation of the alleles. From the paper, "Finally, the pattern of nucleotide variation observed among Mc1r alleles from the Pinacate site suggests the recent action of positive selection. Thirteen polymorphic sites are variable among the light haplotypes, whereas only one site is variable among the dark haplotypes (Table 1). " This means that the dark allele had gone through a much more recent selection event than the light allele. Therefore, the dark allele emerged after the light allele.
3. Age of the lava fields. As was demonstrated above, you need black lava fields in order to have the dark allele. So how old are the lava fields? Very recent, geologically speaking. They are around 1 million years old, much younger than the desert landscape that the ancestral populations adapted to. As shown by both the nucleotide variation and selection pressures, the recent appearance of the lava fields is just one more piece of evidence showing that the dark allele arose through recent mutations in a population that did not have dark fur.
Again this sounds awfully teleological.
That is what the thread on antibiotic resistance is all about. I would love to see your participation in that thread:
EvC Forum: Application of the Scientific Method: Antibiotic Resistance
which would also be the case if the dark allele were a regularly occurring but recessive variation.
It is dominant, and it is immediately selected out of populations that live on the original, light colored desert that existed for eons before the black lava fields appeared.
You know this absolutely for sure?
As sure as anything can be.

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 82 of 1034 (691844)
02-25-2013 3:41 PM
Reply to: Message 79 by Faith
02-25-2013 3:37 PM


Re: Ring Species -- Greenish Warbler -- and Genetic Diversity
Yes but you keep trying to make this equal to the effect of the reduction through the selection and isolation processes and I don't think it is by a long shot.
Why don't you think it is equal?
Isn't rain equal to the rate at which water flows down a river? Can I claim that all rivers should dry up in a single year because rain doesn't exist? Afterall, once rain lands it flows downhill too so you can't get an increase in river water. They should all dry up.
You think at that point you're going to get further beneficial mutations that just increase the diversity again but as a matter of fact it hasn't happened with the cheetah, and what they worry about is that they're only going to get deleterious mutations anyway.
It hasn't? And you know this how? Have you been sequencing the genomes of every cheetah born and testing those observed mutations for beneficial effects?

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 85 of 1034 (691853)
02-25-2013 5:55 PM
Reply to: Message 84 by Faith
02-25-2013 5:44 PM


Re: Mutations Don't Add Anything That Could Rescue the ToE
It is hard to figure out how to get this said, but perhaps I'll eventually have a better way. I keep trying to show that whenever you have the creation of a new phenotype or breed you have the opposite of what evolution would need in order to be true, you have a situation with a built in ultimate ending point.
How so?
I've said that mutation only makes changes in the allele and that's part of it, since you'll never get beyond the boundary of the Kind or "baramin," beyond microevolution, with mere alleles for existing traits within the species that is evolving. All you'll get is variations on the traits that are built into the genome for that species. That is never going to lead to macro-evolution.
You have said that, but you have never brought forth evidence to back that claim. Now would be the time for that evidence.
And I've also said that mutation is only a source of alleles and it doesn't matter what the source is because once the selecting and isolating processes get to work on them to bring out a new phenotype you get the reduction in genetic diversity that always occurs in the formation of new phenotypes, and at the extreme there is no further evolution that is possible.
Why can't you have additional mutations after a selection process that keeps evolution moving? Why can't you have thousands of alleles all being selected for in parallel within a population while also having mutation continually producing more alleles that are passed through selection?
What is stopping the continual accumulation of mutations leading to a continual change in morphology and physiology?
Now I do think just these two observations . . .
They weren't observations. They were empty assertions backed by zero evidence.
and you are still going to end up with the reduced genetic diversity in the end that spells FINIS to the ToE.
Until the next generation is born with mutations that increase genetic diversity.

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Taq
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Posts: 10195
Joined: 03-06-2009
Member Rating: 3.2


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Message 86 of 1034 (691854)
02-25-2013 6:15 PM


Humans and Chimps
To get this into the real world, perhaps you can give us some criteria to use when looking at real life genetic data.
I think we both agree that humans are different from chimps because the DNA sequence of our genomes is different. You would also contend that humans and chimps are in different baramins. I think you would also contend that the genetic variation between genomes of different chimps is within a baramin.
So I would like to know why the genetic differences between humans and chimps could not be produced by mutations, but the genetic differences between chimps could be produced by mutations. Can you explain why the process of mutation can do one, but not the other?
Edited by Taq, : No reason given.

  
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