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Author Topic:   Evolution Requires Reduction in Genetic Diversity
herebedragons
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Posts: 1298
From: Michigan
Joined: 11-22-2009
Member Rating: 4.7


(1)
Message 976 of 1034 (760238)
06-18-2015 11:39 PM
Reply to: Message 969 by PaulK
06-17-2015 5:16 PM


Re: Back to HBD's Chart: Trying New Wording
As a consequence selection is positive when the allele is rare and negative when it is common. (It requires some thought but it does work out)

I think this describes frequency dependent selection, not heterozygote advantage. I have been trying to figure out how that would work, but I'm not sure what you had in mind.

For heterozygote advantage the allele frequency is dependent on the fitness of the homozygotes. If the relative fitness of both homozygotes is equal, the frequency of each allele will be 0.50. If the fitness of one homozygote is higher than the other, the allele frequency will be skewed toward the allele in the more favored homozygote.

Another point regarding heterozygote advantage is that the selection pressure against each of the homozygotes (and therefore the relative fitness) comes from different environmental factors. So in the case of sickel cell, the wild-type homozygote is only disfavored in the presence of malaria pressure, so in the absence of malaria there is no fitness disadvantage and there will be selection against the sickel cell allele. Another example is warfarin resistance in rats. Susceptible rats (SS) will be killed by warfarin but homozygote resistant (RR) are vitamin K deficient. So, heterzygotes (SR) have an advantage over either homozygotes. However, in the absence of warfarin or if a sufficient supply of vitamin K can be obtained, the advantage is negated.

Anyway, negative frequency dependent selection (when fitness increases as a genotype gets rarer) is another way, in addition to heterozygote advantage) that diversity can be maintained or even increased.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 969 by PaulK, posted 06-17-2015 5:16 PM PaulK has responded

Replies to this message:
 Message 977 by PaulK, posted 06-19-2015 3:26 AM herebedragons has responded

  
PaulK
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Posts: 12565
Joined: 01-10-2003
Member Rating: 2.3


Message 977 of 1034 (760241)
06-19-2015 3:26 AM
Reply to: Message 976 by herebedragons
06-18-2015 11:39 PM


Re: Back to HBD's Chart: Trying New Wording
Perhaps I have misunderstood the terminology, but it seems to me that heterozygote advantage must describe a case where the heterozygote has an advantage over both homozygotes, which is exactly the situation with sickle-cell in malarial regions. If that is not correct I think the term needs to be carefully explained when introduced because it is not obvious. As I have said, an advantage to the heterozygote over both homozygotes will have the consequence of what you called frequency-dependent selection although I would think that a more general term.

I have thought a little more on the matter and it does seem that in this case diversity measured by the proportion of heterozygotes would increase, although diversity measured by the number of different alleles would not. Although this could also be said for selection in general, it is more marked in cases like this.

Edited by PaulK, : No reason given.


This message is a reply to:
 Message 976 by herebedragons, posted 06-18-2015 11:39 PM herebedragons has responded

Replies to this message:
 Message 978 by herebedragons, posted 06-19-2015 7:35 AM PaulK has responded

    
herebedragons
Member
Posts: 1298
From: Michigan
Joined: 11-22-2009
Member Rating: 4.7


Message 978 of 1034 (760252)
06-19-2015 7:35 AM
Reply to: Message 977 by PaulK
06-19-2015 3:26 AM


Re: Back to HBD's Chart: Trying New Wording
Perhaps I have misunderstood the terminology, but it seems to me that heterozygote advantage must describe a case where the heterozygote has an advantage over both homozygotes, which is exactly the situation with sickle-cell in malarial regions. If that is not correct I think the term needs to be carefully explained when introduced because it is not obvious.

Sorry, you got the description of heterozygote advantage right and sickel-cell is an example. I was commenting only on the part I quoted...

PaulK writes:

As a consequence selection is positive when the allele is rare and negative when it is common. (It requires some thought but it does work out)

which doesn't fit heterozygote advantage

I have thought a little more on the matter and it does seem that in this case diversity measured by the proportion of heterozygotes would increase, although diversity measured by the number of different alleles would not.

It will push allele frequency to an equilibrium point that is dependent on the relative fitness of the homozygotes rather than Hardy-Weinberg, so it could increase allelic diversity until that equilibrium is reached.

I am sure this could be modeled mathematically but I would have to look it up (I will if anyone is interested)

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 977 by PaulK, posted 06-19-2015 3:26 AM PaulK has responded

Replies to this message:
 Message 979 by PaulK, posted 06-19-2015 11:23 AM herebedragons has responded

  
PaulK
Member
Posts: 12565
Joined: 01-10-2003
Member Rating: 2.3


Message 979 of 1034 (760272)
06-19-2015 11:23 AM
Reply to: Message 978 by herebedragons
06-19-2015 7:35 AM


Re: Back to HBD's Chart: Trying New Wording
quote:

which doesn't fit heterozygote advantage

For cases like sickle-cell where selection maintains a balance between alleles it must be the case. Maybe there are cases where it isn't true, and it may depend on relative fitnesses but I'm pretty sure that it is for sickle-cell.


This message is a reply to:
 Message 978 by herebedragons, posted 06-19-2015 7:35 AM herebedragons has responded

Replies to this message:
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NoNukes
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Posts: 9439
From: Central NC USA
Joined: 08-13-2010
Member Rating: 2.8


Message 980 of 1034 (760311)
06-20-2015 3:05 AM
Reply to: Message 974 by herebedragons
06-18-2015 10:47 PM


Re: Back to HBD's Chart: Trying New Wording
SELECTION: My first take:
Selection replaces one trait with another or its allele with another, so it subtracts diversity from B

Most of the time this is how selection works.

Perhaps I am looking at a wording problem that you find insignificant, but selection does not replace anything. Selection is operates on traits already present and favors animals with trait over animals with variations not including the trait. It does tend to subtract diversity other than in those special cases you discuss.

But replacing traits? No, that requires selection in combination with mutation or other forces. Maybe 'displace' would be a better verb.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

History will have to record that the greatest tragedy of this period of social transition was not the strident clamor of the bad people, but the appalling silence of the good people. Martin Luther King

If there are no stupid questions, then what kind of questions do stupid people ask? Do they get smart just in time to ask questions? Scott Adams


This message is a reply to:
 Message 974 by herebedragons, posted 06-18-2015 10:47 PM herebedragons has responded

Replies to this message:
 Message 981 by Faith, posted 06-20-2015 7:50 AM NoNukes has responded
 Message 982 by Admin, posted 06-20-2015 7:53 AM NoNukes has acknowledged this reply
 Message 983 by herebedragons, posted 06-20-2015 9:54 AM NoNukes has acknowledged this reply

    
Faith
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Posts: 24418
Joined: 10-06-2001
Member Rating: 1.0


Message 981 of 1034 (760312)
06-20-2015 7:50 AM
Reply to: Message 980 by NoNukes
06-20-2015 3:05 AM


Re: Back to HBD's Chart: Trying New Wording
HBD got it right: alleles for two traits already available, one replaces the other. Trust you to misread me as usual.
This message is a reply to:
 Message 980 by NoNukes, posted 06-20-2015 3:05 AM NoNukes has responded

Replies to this message:
 Message 984 by NoNukes, posted 06-20-2015 10:23 AM Faith has not yet responded

    
Admin
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Posts: 12433
From: EvC Forum
Joined: 06-14-2002
Member Rating: 2.1


Message 982 of 1034 (760313)
06-20-2015 7:53 AM
Reply to: Message 980 by NoNukes
06-20-2015 3:05 AM


Moderator Clarification
As you say, it may be a wording issue. I think that when HBD says "Selection replaces one trait with another..." that he means changing things like beak size or fur color or melanic coloration by drawing upon variation already present in the genome.

--Percy
EvC Forum Director

This message is a reply to:
 Message 980 by NoNukes, posted 06-20-2015 3:05 AM NoNukes has acknowledged this reply

    
herebedragons
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Posts: 1298
From: Michigan
Joined: 11-22-2009
Member Rating: 4.7


(3)
Message 983 of 1034 (760328)
06-20-2015 9:54 AM
Reply to: Message 980 by NoNukes
06-20-2015 3:05 AM


Adaptive landscapes and selection (also for Faith)
Perhaps I am looking at a wording problem that you find insignificant, but selection does not replace anything.

Yea, I struggled a little with the wording but decided not to make an issue of it at this time. I didn't think she had meant replace as in "substitutes" but rather as in "becomes more prevalent," so I just ignored it. The important thing at this time was just making the chart clear.

Selection is operates on traits already present and favors animals with trait over animals with variations not including the trait.

Right. In reality, selection acts on variation within a population and shifts the mean of that variation to a different optimum. Strong selection (especially when coupled with drift) can push a trait or an allele to fixation, but it is typically beneficial to the population to maintain some variation. Since environmental conditions and therefore selection pressures are rarely static, maintaining variation allows the population to respond to changing selection pressures. In addition, traits that are controlled by a single locus are more likely to go to fixation because of selection than polygenic (influenced by multiple genes) traits. Since the majority of traits are plolygenic, fixation of a trait is difficult.

If you are familiar with the concept of an adaptive landscape (or fitness landscape), I think they are great for helping to visualize the concept of selection. The thing that an be confusing is that it can be easy to look at them as representing spacial relationships, but they don't. These "maps" have nothing to do with how close individuals are to one another but how combinations of alleles or traits are favored by selection and how those combinations change over time.

Below is a dynamic landscape where the optimum of a trait is shifting back and forth.

The X and Y axis can be the combination of alleles or some measure of a trait. The Z axis is fitness with up being increased fitness. This could represent the peppered moths whose color morphs shift back and forth depending on environmental conditions. Notice how the variation never goes away, it just shifts to a new mean when there is a new optimum.

The adaptive landscape below shows a situation where there are multiple fitness peaks and the population evolves up only one of those peaks.

Notice a smaller population begins to climb the peak on the left but disappears? This could be due to genetic drift but gene flow is probably involved as well. As one subset of the population climbs higher up on the fitness peak, it's combination of alleles are more fit and would be "replacing" or more appropriately, displacing alleles at those lower fitness levels by interbreeding.

I wish I could stop the .gif image at a specific spot so you can see exactly the point I am talking about, but watch the image as the population splits into two groups - one on the left and one on the right. (Again, this is not a spatial representation - it can be hard to keep that in mind). Now if an individual high up on the right hand peak mates with an individual in the group on the left, a portion of the offspring will have this more fit combination of alleles and so will become part of the group on the right. In this way, the combination of alleles or traits in the group on the left is being displaced.

Theoretically, the groups could climb the different peaks and so would be differentiated (sympatric speciation), but as long as there is gene flow between those groups it is unlikely because of the situation I described above.

These adaptive landscape .gifs also visually show selection acting to reduce variation WITHIN the population. You can especially see it in the dynamic model when selection is released, the variation in the population increases until it begins moving up the adaptive peak.

HBD

--------------
Author of .gif fitness landscape maps: "Visualization of a population evolving in a dynamic fitness landscape" by Randy Olson and Bjørn Østman - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons -


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 980 by NoNukes, posted 06-20-2015 3:05 AM NoNukes has acknowledged this reply

  
NoNukes
Member
Posts: 9439
From: Central NC USA
Joined: 08-13-2010
Member Rating: 2.8


Message 984 of 1034 (760329)
06-20-2015 10:23 AM
Reply to: Message 981 by Faith
06-20-2015 7:50 AM


Re: Back to HBD's Chart: Trying New Wording
HBD got it right: alleles for two traits already available, one replaces the other. Trust you to misread me as usual.

As I wrote, 'replace' seems to be a bad way to express the selection because it does not indicate why the result of selection can be to reduce diversity. Literally replacing one trait with another would simply preserve diversity. In the population undergoing selection, we may have multiple traits existing and selection tends to increase the appearance of one of the traits at the expense of one or more others. Replace, in my view does not get anywhere close to expressing that. Displace seems to work better or would any wording expressing a trade off.

More to the point, what is your problem, Faith? I thought your wording was off, so I asked a question. Here is the beginning of HBD's post:

HBD writes:

Yea, I struggled a little with the wording but decided not to make an issue of it at this time.

I understand that you have a problem in particular with my making corrections to what you are saying, but you probably should just get over that.

Edited by NoNukes, : No reason given.


Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846)

History will have to record that the greatest tragedy of this period of social transition was not the strident clamor of the bad people, but the appalling silence of the good people. Martin Luther King

If there are no stupid questions, then what kind of questions do stupid people ask? Do they get smart just in time to ask questions? Scott Adams


This message is a reply to:
 Message 981 by Faith, posted 06-20-2015 7:50 AM Faith has not yet responded

    
herebedragons
Member
Posts: 1298
From: Michigan
Joined: 11-22-2009
Member Rating: 4.7


Message 985 of 1034 (760717)
06-24-2015 11:59 PM
Reply to: Message 944 by Faith
06-16-2015 8:32 AM


Re: Back to HBD's Chart: Drift
How does this show up in actuality. That is, can you recognize drift just by looking at a population, of, say, a herd animal? And what would you see?

Drift shows up as random fluctuations in allele frequency. In order to see the effects of drift, you would need to look at several generations. Since most traits are polygenic (that is, controlled by more than one gene and having a continuous distribution), it would be difficult to “see” changing allele frequencies over a few generations without doing genetic samples. You could easily see the effect with an annual flower in which flower color is controlled by a single gene. What you would see is a fluctuating number of colored flowers - one year there would be more blue flowers than white; the next year white would be more prevalent, ect.

I've had the general picture in mind of a subpopulation forming within a population but apparently this isn't correct?

Well, in theory a subpopulation could form within a larger parental population, but how often that actually happens is debatable. Moreover, drift would probably not be the factor involved; rather it would be selection and mutation.

The concept of "sampling error" has never made any sense to me although I've encountered it many times in reading about drift. I don't know what to picture.

The easiest way to picture sampling error is flipping a coin. A coin could land either heads or tails so there is a 50% chance that it will land on heads. If we flip it 10 times in a row we would expect that it would land on heads 5 times and tails 5 times. However, there is in fact only a 25% chance that if you flip a coin 10 times you will get 5 heads. There is actually a 21% chance that you will get either 4 or 6 heads. This would be a 10% error from the expected value. If you flip the coin 100 times, there is only an 8% chance that you will get 50 heads and only a 1% chance that you will get only 40 or 60 heads (10% error).

The effect of this sampling error on organisms is that the offspring of a generation vary in allele frequency from the expected frequencies. The effect is more pronounced in small populations than in large populations.

Below are binominal distributions for n=10, n=100 and n=1000.

Notice that as sample size increases the probability of having exactly 50% success rate (heads) decreases from ~25% (n=10) to ~8% (n=100) to ~2.5% (n=1000). Also the range of error decreases from 20% (n=10) to 10% (n=100) to 5% (n=1000).

What is another source? How much occurs at the gamete level?

Another source of drift can be when individuals are removed from a population by serendipitous events such as natural disasters. Imagine a population of birds on an island when a hurricane strikes and kills half of them. Chances are that allele frequency after the event will be different from the frequencies before. This is a type of drift, yes, and often what the common perception of drift is. However, it is not really where the majority of drift comes from.

Some gametes fail to fuse with another gamete (for example, think of how many sperm are produced in mammals with only 1 or 2 that fertilize the egg) and of those that do form zygotes, only a small proportion may survive. Think about a fish that may lay thousands of eggs but most of them are eaten when they are still fry. This "sampling" is likely to result in a different allele frequency than that of the parent population.
And yet this is normal, it's how the reproductive system works, so why is there this apparently to-be-expected "error?"

How could there not be this sampling error considering how the reproductive system works?

Here is an image of experimental populations of Tribolium (flour beetles) that shows the result of drift.

If the beetle is homozygous for the wild-type allele (b+), it is black. If it homozygous for the mutant allele (b), it is red. The heterozygotes are brown and can be easily identified.

Populations were founded with 10, 20, 50 and 100 heterozygote individuals (5, 10, 25 and 50 breeding pairs) and each generation was maintained at that population level by randomly selecting the next generation. Each population size had 12 replicate populations and 240 individuals from each generation were rated as bb, bb+ or b+b+. The frequency of the wild-type allele (b+) for each population and each generation are plotted on the chart.

Notice for the population with n=10, that 6 populations fixed the b+ allele (went to 100%) and 1 population fixed for the b allele (went to 0%). But for the n=100 no populations fix for either allele. Notice also that allele frequencies bounce around, especially in the smaller populations. Also notice the trend in increase of the wild-type allele. This appears to be due to selection or a disadvantage to the mutant allele.

I hope that helps to better explain how drift works.

Also, if you haven't already, check out Message 983 about selection.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 944 by Faith, posted 06-16-2015 8:32 AM Faith has responded

Replies to this message:
 Message 986 by Faith, posted 06-25-2015 7:42 AM herebedragons has responded

  
Faith
Member
Posts: 24418
Joined: 10-06-2001
Member Rating: 1.0


Message 986 of 1034 (760732)
06-25-2015 7:42 AM
Reply to: Message 985 by herebedragons
06-24-2015 11:59 PM


Re: Back to HBD's Chart: Drift
You've put up a lot of information to digest but for a while I'm not going to have the time for it. And most of it looks to be peripheral at best to the argument I've been pursuing. The Fitness Map is just going to drive me crazy though.
This message is a reply to:
 Message 985 by herebedragons, posted 06-24-2015 11:59 PM herebedragons has responded

Replies to this message:
 Message 987 by herebedragons, posted 06-25-2015 8:23 AM Faith has not yet responded
 Message 990 by herebedragons, posted 09-25-2015 1:15 PM Faith has not yet responded
 Message 991 by RAZD, posted 09-25-2015 2:03 PM Faith has not yet responded
 Message 992 by RAZD, posted 09-26-2015 11:16 AM Faith has not yet responded

    
herebedragons
Member
Posts: 1298
From: Michigan
Joined: 11-22-2009
Member Rating: 4.7


Message 987 of 1034 (760741)
06-25-2015 8:23 AM
Reply to: Message 986 by Faith
06-25-2015 7:42 AM


Re: Back to HBD's Chart: Drift
You've put up a lot of information to digest but for a while I'm not going to have the time for it.

Understandable. As you can see, I am not able to post consistently either.

most of it looks to be peripheral at best to the argument I've been pursuing.

It is peripheral in that it is background information. The argument you have been pursuing looks nothing like what we see when we study the genetic diversity of natural populations. But there is just no simple answer to your argument without explaining how we actually study diversity and what the results of those studies imply. One of the creationist claims is that we are all working with the same data, just interpreting it differently. But we are NOT working with the same data here - not at all. I am trying to explain what the data is that we work with; which tells a completely different story than the one you are arguing.

So, do we all work with the same data and just interpret it different... or are creationists happy to only consider a tiny piece of the information available and draw conclusions from just that?

The Fitness Map is just going to drive me crazy though.

Why? Because it looks like it represents spacial distribution? That's understandable. Think of it as a genetic diversity map. Each individual on the map represents a particular genotype, a particular combination of alleles or traits. The landscape is how that genotype (or phenotype) interacts with the environment. The individuals higher up on the landscape will bear more offspring than those lower on the landscape because of this interaction between genotype (phenotype) and environment.

Also remember that these models are computer simulations. They are meant to be illustrations of a concept, not representations of some specific data.

I hope to be able to discuss some ways we actually measure diversity and how we analyze and use that data. To analyze total genetic diversity of a population (that is the total number of alleles at all loci) is impractical at best and essentially impossible with our current capabilities. So understanding how we actually measure and analyze diversity is important to this discussion. This background information is important to understanding how and why we make certain predictions about diversity and the signals we are looking for when we analyze it.

Taking our time is not a problem.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 986 by Faith, posted 06-25-2015 7:42 AM Faith has not yet responded

  
herebedragons
Member
Posts: 1298
From: Michigan
Joined: 11-22-2009
Member Rating: 4.7


Message 988 of 1034 (760745)
06-25-2015 8:44 AM
Reply to: Message 979 by PaulK
06-19-2015 11:23 AM


Re: Back to HBD's Chart: Trying New Wording
For cases like sickle-cell where selection maintains a balance between alleles it must be the case. Maybe there are cases where it isn't true, and it may depend on relative finesses but I'm pretty sure that it is for sickle-cell.

I realized what the wording was that I took issue with. It was that selection was dependent on whether the allele was "rare" or "common" which isn't quite right. Here is my description of heterozygote advantage again for clarity:

HBD writes:

For heterozygote advantage the allele frequency is dependent on the fitness of the homozygotes. If the relative fitness of both homozygotes is equal, the frequency of each allele will be 0.50. If the fitness of one homozygote is higher than the other, the allele frequency will be skewed toward the allele in the more favored homozygote.

Another point regarding heterozygote advantage is that the selection pressure against each of the homozygotes (and therefore the relative fitness) comes from different environmental factors. So in the case of sickel cell, the wild-type homozygote is only disfavored in the presence of malaria pressure, so in the absence of malaria there is no fitness disadvantage and there will be selection against the sickel cell allele. Another example is warfarin resistance in rats. Susceptible rats (SS) will be killed by warfarin but homozygote resistant (RR) are vitamin K deficient. So, heterzygotes (SR) have an advantage over either homozygotes. However, in the absence of warfarin or if a sufficient supply of vitamin K can be obtained, the advantage is negated.

So in the case where the fitness of both homozygotes is equal and the equilibrium frequency is 0.50, if the frequency of one allele falls to 0.49 (the other would be 0.51), selection would work to push the frequency back to 0.50. Which I guess you could describe as "rare" or "rarer," but I don't think it accurately describes the situation.

Maybe Faith is right and I am a "pedantic nitpicker," but hey, that's what we scientists do .

But I didn't comment so much as to say you were wrong, but to give a better and more complete description of how heterozygotic advantage works and why.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 979 by PaulK, posted 06-19-2015 11:23 AM PaulK has not yet responded

  
RAZD
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Posts: 18257
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 3.3


(1)
Message 989 of 1034 (769811)
09-25-2015 9:02 AM
Reply to: Message 954 by Faith
06-16-2015 10:33 AM


revived thread
I'm reviving this thread because a lot of what Faith is saying on the Evolution. We Have The Fossils. We Win. thread is just a duplication of what is here, and I'm going to say a bunch of things here to refer to rather than clog that thread up.

So the question to you would be: do you think humans have reached the end of the road if they have made these varieties but have not made a new species?

The end of the road isn't reached until all genetic possibilities have been exhausted. Human beings have a lot of genetic diversity left as far as I can see.

And obviously we are nowhere near the end of the road when species keep appearing.

Genetic drift doesn't care about how a species looks, survives or mates, etc.

It is SO unnecessary and confusing and a waste of time to say such things.

Sorry, but it is necessary to continually point out when terms are misused or misunderstood.

Those that survive are the parents of the next generation. What alleles they have would not confer an advantage to survive another eruption.

That is in many ways quite similar to the population splits I've been talking about, being a random selection of alleles without any regard to fitness, except all the genetic stuff survives rather than dying as in drift.

You still sound confused. Or is it just poorly worded: all the "genetic stuff" dies?

I would not say "favoring" as that implies some intrinsic value to the survivors compared to the victims that doesn't exist.

The word "random" is supposed to take care of that implication. Could say "selection" again but that has the same implication. I can't think of a word for the phenomenon that wouldn't have that implication.

Isn't that what I said? I understand the process, what is apparently needed as a more neutral term and I can't come up with one.

Random distribution.

... Why wouldn't the new allele frequencies created by the initial formation of the band of migrants be enough to explain it?

Same old alleles different frequencies, still not enough to be that different from the parent population to account for the world wide variation seen.

I'm absolutely certain it is, just as you all think not, and there really isn't any proof one way or the other. You imagine mutations making the big differences, where's the evidence?

A different distribution of alleles is sufficient to form a different variety but not a new species that is genetically incompatible -- the evidence is that they were compatible in the parent population.

You have to have new alleles not in the parent population for genetic incompatibility to occur.

Changes would be due to mutations and genetic drift, so that things like skin color and eye color and hair color and hair curliness\straightness etc would vary from one population to the other.

All that is built into the human genome, new traits emerging when new allele frequencies favor it.

Except that it isn't. You can't get blue eyes in a population that does not have blue eye alleles by dividing that population into smaller populations. But I can get blue eyes in a population that does not have blue eye alleles by mutation.

These mutations, while not necessarily selected do still mean that the mutations can be tracked from population to population, and from that analysis determine the general paths of migration of the exploratory populations.

What's being tracked is built-in allelic possibilities, called mutations from the ToE belief in mutations.

Not up to looking at a link right now. (The Human Journey: Migration Routes )

If they were built-in then the distribution analysis would not work.

What evidence? The evidence is that mutations accomplish very little of use to any organism. ... There is NO evidence that mutations are the source of healthy alleles, some flukes where their errors manage to do something useful, but very rare flukes.

The black pocket mice for example - being black by mutation they could then take advantage of the lava beds where black was beneficial compared to tan.

That's the only example anyone can come up with. ...

Show me the evidence! WHAT you HAVE evidence? Anyone could come up with THAT, but it's ONLY ONE!

I mean really, Faith. One piece of evidence is enough to show that it has happened. Biologists don't expect to find evidence like this often, but they do expect mutations to occur because we know they occur. More often than is necessary.

... Raises some questions about how mutations manage to show up for the occasion.

What occasion? Mice living beside volcanic rock for thousands of years before a mutation occurs that allows some mice to survive within the lava fields is an "occasion"??? Really? No, it is a random mutation that occurs and the mice with the mutation were able to take advantage of an ecology the parent population could not use.

On the other hand, if the allele were "built-in" to the genome then there is no reason to wait for it to occur, mice would move into the lava fields and presto chango the trait would "emerge" ...

Which doesn't explain why two different populations have two different mutations.

Yes your "hypothesis" has been refuted.


..... enough for now. As anyone can see it is the same argument being pushed on the other thread, and it would be better to discuss it here.

Enjoy


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This message is a reply to:
 Message 954 by Faith, posted 06-16-2015 10:33 AM Faith has not yet responded

  
herebedragons
Member
Posts: 1298
From: Michigan
Joined: 11-22-2009
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(1)
Message 990 of 1034 (769842)
09-25-2015 1:15 PM
Reply to: Message 986 by Faith
06-25-2015 7:42 AM


Moving discussion from Fossil thread
Message 154

HBD writes:

While major structural changes may be impossible for "tape-reader genetics," they are not so for the intricate, mega-networks of real genetics.

Faith writes:

Show me that ANY structural changes occur in normal genetics.

Essentially you have framed this request so that it cannot be answered satisfactorily. First of all, what is "normal" genetics? I am pretty sure our understandings of "normal" genetics are quite different. By "normal" genetics do you mean the kind that leads to "genetic depletion?" Cause I don't think that is normal. And I am pretty sure the kinds of things we look at genetically when trying to unravel issues like this will not seem "normal" to you. Heck, we could barely get past the basics of selection, drift, mutation and migration; how could we move into the deeper water of developmental genetics?

Secondly, I am pretty sure that what you have in mind for "structural change" is beyond the scope of what we observe in the course of "normal" genetic studies. Most of the examples we have from experimental studies are relatively minor compared to what we see in the fossil record, and I imagine to you it will be a matter of "it's still a fish; a bacterium; a plant, etc..." I fell like you are expecting the proverbial dog turning into a cat right before our very eyes; and that just doesn't happen. However, we have documented flies that have developed legs where their eyes should be, which I would say is a major structural change, but somehow I don't think that is what you have in mind either.

What the examples we do have show is how these kind of changes can arise. They show how turning on and off different switches can affect development and how those effects can lead to significant structural changes. But by all means we have not unraveled but a small, small portion of the secrets of developmental biology. There is much work to be done, but we do have enough evidence to suggest that the kind of changes we see in the fossil record are not only possible but are also probable.

I will try to post a couple examples this weekend, but I doubt you will be all that impressed.

HBD


Whoever calls me ignorant shares my own opinion. Sorrowfully and tacitly I recognize my ignorance, when I consider how much I lack of what my mind in its craving for knowledge is sighing for... I console myself with the consideration that this belongs to our common nature. - Francesco Petrarca

"Nothing is easier than to persuade people who want to be persuaded and already believe." - another Petrarca gem.

Ignorance is a most formidable opponent rivaled only by arrogance; but when the two join forces, one is all but invincible.


This message is a reply to:
 Message 986 by Faith, posted 06-25-2015 7:42 AM Faith has not yet responded

  
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