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Author Topic:   A Creationist's view of Natural Limitation to Evolutionary Processes (2/14/05)
nator
Member (Idle past 2286 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 166 of 218 (341362)
08-19-2006 11:41 AM
Reply to: Message 157 by Faith
08-19-2006 3:02 AM


Sure bad (and in this case I mean bad to the individual in the long term, like my keratoconus) mutations can slip past the reproduction filter, but so do good and neutral mutations that can counter or modify those bad ones.
quote:
So far in this discussion there have been no examples of these, only examples of "neutral" mutations that cause disease.
As I have mentioned several times before, I have a neutral/beneficial mutation.
In a gene called "MSX1", I have a mutation which prevented my lower wisdom teeth from ever forming.
There is also a mutation which conferrs partial to full immunity to the HIV virus. It turns out that the HIV virus is quite similar to the virus that causes Bubonic Plague, and several families who were survivors of the Black Plague in Europe centuries ago happened to have a mutation that prevented the virus from doing what it did to nearly everyone else. The decendents of those Plague survivors have inherited that mutation and are now benefitting from it now that the environment has had a similar virus introduced into it.
The above example is much the same as what happens with antibiotic resistance.
Another example of a beneficial mutation is Sickle Cell Disease.
From the wiki bold added by me:
The sufferers of the illness have a reduced life span. It is believed that carriers (sickle cell trait) are relatively resistant to malaria. Since the gene is incompletely recessive, carriers have a few sickle red blood cells at all times, not enough to cause symptoms, but enough to give resistance to malaria. Because of this, heterozygotes have a higher fitness than either of the homozygotes. This is known as heterozygote advantage.
The malaria parasite has a complex life cycle and spends part of it in red blood cells. In a carrier, the presence of the malaria parasite causes the red blood cell to rupture, making the plasmodium unable to reproduce. Further, the polymerization of Hb affects the ability of the parasite to digest Hb in the first place. Therefore, in areas where malaria is a problem, people's chances of survival actually increase if they carry sickle cell anemia.
Due to the above phenomenon, the illness is still prevalent, especially among people with recent ancestry in malaria-stricken areas, such as Africa, the Mediterranean, India and the Middle East. In fact, sickle-cell anemia is the most common genetic disorder among African Americans; about 1 in every 12 is a carrier.
The evolution of sickle-cell anaemia is probably an example of Baldwinian evolution, whereby humans modify their environment and thus change the selective pressures. As humans in tropical areas in Africa and elsewhere developed agriculture and animal husbandry, they expanded the niche for Anopheles mosquitoes that could transmit the malaria parasite.
In the USA, where there is no endemic malaria, the incidence of sickle cell anaemia amongst African Americans is much lower than in West Africa and falling. Without endemic malaria from Africa, the condition is purely disadvantageous, and will tend to be bred out of the affected population. See the Price equation article for a simplified mathematical model of the genetic evolution of sickle cell anemia.
Edited by schrafinator, : No reason given.

"Science is like a blabbermouth who ruins a movie by telling you how it ends! Well I say there are some things we don't want to know! Important things!"
- Ned Flanders
"Question with boldness even the existence of God; because, if there be one, he must more approve of the homage of reason than that of blindfolded fear." - Thomas Jefferson

This message is a reply to:
 Message 157 by Faith, posted 08-19-2006 3:02 AM Faith has replied

Replies to this message:
 Message 169 by Faith, posted 08-19-2006 2:26 PM nator has replied

nator
Member (Idle past 2286 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 167 of 218 (341368)
08-19-2006 11:51 AM
Reply to: Message 164 by Percy
08-19-2006 11:10 AM


quote:
For instance, I believe german shepherds have a genetic defect that causes hip problems, but we treat the hip problems and allow the dogs to reproduce. Of course, it was humans who bred german and shepherds and all other dogs from wolves, anyway, so perhaps this is too artificial an example. But you probably get the idea.
Yes, Percy, hip displaysia is the disorder, and other breeds of dogs get it too. Collies are prone to having retinal problems and certain horse breeds are known to be prone to certain degenerative chronic foot and leg problems for the same reasons.
All of these maladies are a result of artificial selection for the whims of human aesthetics, though.

This message is a reply to:
 Message 164 by Percy, posted 08-19-2006 11:10 AM Percy has not replied

Faith 
Suspended Member (Idle past 1561 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 168 of 218 (341394)
08-19-2006 1:42 PM
Reply to: Message 164 by Percy
08-19-2006 11:10 AM


Far from ignoring the point, this IS the point. Since the defective genes are passed on we have a state of increasing genetic disease in the population.
Only if there's no selection is there a situation of increasing genetic defects in a population, which may be the precise case for homo sapiens. If that's your point, then I agree with you. One of the dangers the human race poses for its own survival is that our ability to develop medical treatments for genetic diseases allows people with genetic defects, who in earlier times would have died young, to produce offspring.
Definitely, and this has to be sorted out from defects which are simply passed on "in the wild" because they are not selected out because they do not affect reproduction, which is the situation I think is being discussed here. However, it may need to be rethought in the case of diabetes, which Ramoss brought up in Message 148. The gene may be passed on, in fact it seems to be associated with fewer miscarriages according to him, but if this gene must pair with a similar gene in order to produce the disease, childhood diabetes, which is fatal without the medical intervention we now take for granted, then all we have is proliferating genes in the population and not the disease itself. BUT this very situation increases the chances of the combination that produces the disease.
And what is a "gene for diabetes" anyway? I have trouble thinking of a normal function, a gene, in terms of producing a disease. Is a "gene for diabetes" a gene mutated from a gene that regulates blood sugar in a beneficial way perhaps, or something like that? Isn't there some way to describe it in terms of a genetic defect, or is it simply that the way it sprawls there along the DNA chain it looks and acts for all the world like any other gene so you can't make such a distinction?
One extremem example that comes to mind is cystic fibrosis. Individuals with this genetic defect used to die young, but modern medicine now allows many to live into their 40's. Because cystic fibrosis is an extreme example where every victim is intimately familiar with the consequences of the disease, victims probably rarely pass this gene on. They either choose not to have children, or they use genetic screening to check for the presence of two defective copies of the CFTR gene before birth and terminate the pregnancy.
For the sake of this discussion it would be good to confine it to mutations that produce diseases that don't in themselves prevent reproduction.
Are all genetic diseases a matter of the combining of two of the same defective genes?
But other less severe genetic defects, like color blindness, are probably passed on all the time. In modern societies the survival cost of color blindness is minimal, but in prehistoric times it was probably much more important. For instance, those with color blindness often have much greater difficulty seeing in the dark.
But it seems to me we can define this as a defect whether or not it interferes with survival.
Actually, there are some questions raised about genetic transmission in this case, though as a side issue. Color blindness is predominantly passed on through males, but I inherited a very mild case of it -- undetectable except on very refined tests -- apparently from my father who had severe red-green color blindness (he distinguished the red signal light from the green one by degree of brightness and position above or below on the pole). I have trouble distinguishing a light pastel shade of yellow-green from the same light shade of orange or peach. I identify them easily in contrast with a stronger color, but they both blur to beige in each other's company. But how does a mild case of anything, or a degree of anything, get passed on? You'd think that you either have two genes for something, which would then be overt rather than nearly undetectable, or you don't have the disease at all. I'm sure there's an answer to this, I just don't happen to have run across it.
Visual acuity and focussing ability also has a genetic component. Darwin observed in Patagonia that the natives all had far better vision than the Europeans. In a civilization without eyeglasses, the genetic ability to produce good eyesight would be well maintained.
Well, maybe, but how would you know for sure that this is a case of natural selection? That would imply that any who were born less visually acute would fail to reproduce because of lack of that acuity, doesn't it? Is this visual acuity the case for all native tribes everywhere? It may just be that the progenitors of the Patagonians happened to have good genes for vision, "selected" purely circumstantially by migration rather than adaptability. (My colorblind father, by the way, also had the most amazing long-distance vision. Could see things miles away, miles down a stretch of endless Nevada highway for instance).
So I think you have a good point for homo sapiens, but we're increasing the defects in our gene pool through articial rather than natural means, usually medically related means. We even do the same thing for our pets. For instance, I believe german shepherds have a genetic defect that causes hip problems, but we treat the hip problems and allow the dogs to reproduce. Of course, it was humans who bred german and shepherds and all other dogs from wolves, anyway, so perhaps this is too artificial an example. But you probably get the idea.
Yes, but we should be trying to avoid these examples for the sake of this discussion and focus only on defects that are passed on without medical intervention.
In the wild, medical means of alleviating the effects of genetic defects are not available, and genetic defects are filtered out, meaning the affected individuals do not survive to produce, or if they do, they produce fewer offspring than unaffected individuals.
Fewer offspring might be relevant here. The examples that have so far come up are Ramoss' example of diabetes and DrJones' example of keratoconus which he says in Message 154 slowly leads to blindness.
And what I am saying is that this means that evolution is really impossible, since not only does speciation lead to decreased genetic variability, but the passing on of diseases in the population leads to overall lack of vigor that all by itself tends to extinction rather than to anything that could produce a healthy species as evolution implies must happen.
You say that evolution is impossible, and I grant that your misunderstanding of evolution is impossible. This is representative of too deep a misunderstanding to take the time to correct.
There is no misunderstanding. I learned the rap about reproduction and selection and survivability etc. back in high school. I am simply pondering some implications of genetic diseases in the last few posts.
I know that's a copout, I'm criticizing without providing the proper counterpoint, but I am pressed for time right now. Please give me a pass on this for now and I'll try to come back to it later.
OK but it's more than a copout, it's "poisoning the well," that is, making sure that you establish firmly in the reader's mind that Faith doesn't know what she's talking about although you haven't proved it.
So far in this discussion there have been no examples of these, only examples of "neutral" mutations that cause disease.
I don't think we should let any formal definitions of "neutral mutations" get in the way of understanding. Whatever those definitions might be, I think your approach makes more sense. Describing as neutral a genetic defect that adversely affects the ability of an organism to produce offspring does not make any sense to us laypeople.
But I wasn't talking about inability to produce offspring. I was talking about the proliferation of disease in the population, or general weakness of one sort or another that would NOT affect ability to reproduce -- apart from medical intervention. I think it very likely that overall the entire human population has generally far less strength of various kinds than was the case a few millennia ago.
Dr. Jones described his keratoconus as a "neutral" mutation. I think there must be many examples of this sort of thing but so far only a couple have come up. Schraf added her example after your post. Simply carrying a defective gene doesn't interfere with reproduction or quality of life in most cases apparently, but if it combines with another of same the effect may be lethal to the offspring, or maybe it won't be, merely cause some awful condition that kills the person slowly after reproductive age, or just produces pain and suffering over a long life.
Evolution seems to assume that genetic defects just happen to crop up from time to time at a probably predictable rate -- always and forever, on the uniformitarian principle -- but that we can count on the various selection processes to weed them out. Seems to me that as long as some don't interfere with reproduction that over time they would increase in the population and make for a rather sickly bunch even if they could survive because of compensating strengths or an accommodating environment. Ultimately such a trend WOULD tend to extinction though, which is simply an extreme selection process after all.
I'm addressing a supposed "neutral" mutation, two of them, both causing disease. The supposed "good" mutations are pretty much a wishful fantasy so far.
Haven't examples of good mutations been provided for you in the past? Anyway, one common type of good mutation is caused by gene duplication. Let's say there's a gene that provides a beneficial protein, say a protein involved in muscle endurance. Now there's a mutation that duplicates this gene, and so muscle cells suddenly start producing twice as much of this muscle endurance protein. That's an example of a beneficial mutation.
I have had trouble following some discussions of supposed good mutations, but in this case you are offering, why is it you can only offer a hypothetical? Why do you have to give a "Let's say..." instead of a known fact? The defective genes and their diseases are facts. Diabetes is a fact. Keratoconus is a fact. (Actually, I just looked it up, and contrary to what DrJones said, the wiki article says it does not lead to blindness.) Cystic fibrosis is a fact. These genetic diseases all are facts, not hypotheses. I've seen long lists of them. Maybe I should look up such a list. {edit: Done: List of genetic diseases and lots of discussion.}
Anyway, I need a factual example of a "good" mutation along the same lines -- and to know why it's considered to be a "mutation" too, rather than just a normal genetic option. And please, no bacteria, only sexually reproducing examples.
Any particular gene can experience many different types of mutation, from simple nucleotide replacement to complete inversion to complete removal. While most potential genetic mutations are either harmful or neutral, some mutations are improvements, and the probability that these mutations will happen is not zero. Hence, given time they are inevitable, and to the extent that they provide an advantage they will propagate throughout a population.
Again, this is merely hypothetical. But as you asked, I will grant you time to come up with some factual examples. AND again, please, a consideration of what makes these "mutations" rather than normal genetic options that show up in the normal course of reproduction.
Edited by Faith, : No reason given.

This message is a reply to:
 Message 164 by Percy, posted 08-19-2006 11:10 AM Percy has replied

Replies to this message:
 Message 170 by crashfrog, posted 08-19-2006 2:27 PM Faith has replied
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 Message 181 by nator, posted 08-19-2006 6:47 PM Faith has replied
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Faith 
Suspended Member (Idle past 1561 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 169 of 218 (341409)
08-19-2006 2:26 PM
Reply to: Message 166 by nator
08-19-2006 11:41 AM


What makes your wisdom teeth mutation "beneficial" in any sense of the word?
In the case of the mutation that confers immunity to the plague and to HIV, how do you know it is a mutation rather than a normally occurring gene? That is, perhaps it's the other way around: perhaps the whole human race once had it but mutations killed it and now it survives only in a few.
Sickle Cell is always trotted out. It appears to be a terrific case of One, and a backhanded claim to beneficial mutation since it causes disease simultaneously.
It's easy to come up with a list of genetic diseases, but notably difficult to come up with any real evidence of beneficial mutations.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.

This message is a reply to:
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Replies to this message:
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crashfrog
Member (Idle past 1584 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 170 of 218 (341410)
08-19-2006 2:27 PM
Reply to: Message 168 by Faith
08-19-2006 1:42 PM


Are all genetic diseases a matter of the combining of two of the same defective genes?
It depends on what the disease is. Imagine inheriting your belt from your mother and your suspenders from your father. You could safely inherit a faulty belt from your mother and suffer no ill effects because the suspenders will hold your pants up; you could instead get faulty suspenders from your father and still suffer no effects because the belt still works.
But if you inherit both a faulty belt and faulty suspenders, you're going to have a disease called "ankle-pants." And you're definately going to pass on something faulty to your children, either the belt or the suspenders; whether or not your children can't hold their pants up is going to depend on whether or not they get faulty belts or suspenders from their father.
Those diseases are chromosomal recessive, they're the disorders you're thinking of when you describe them, incorrectly, as "combining two genes." It's not that Gene A mixes with Gene B to form Disease C; it's that being sexual, diploid organisms means that we have two copies of every gene. If one copy is broken the other can do the job, often. But if both copies are broken you're going to suffer whatever malady is going to result from your body not manufacturing that gene product.
Not all diseases are like this. Some disorders are chromosomal dominant, where simply having inherited one copy of the gene is enough to cause the disease. These disorders are caused by the presence of a gene product that shouldn't be there, rather than the absence of one that should. All it takes is one gene of that kind for the body to start producing something that it shouldn't.
Color blindness is predominantly passed on through males, but I inherited a very mild case of it -- undetectable except on very refined tests -- apparently from my father who had severe red-green color blindness (he distinguished the red signal light from the green one by degree of brightness and position above or below on the pole). I have trouble distinguishing a light pastel shade of yellow-green from the same light shade of orange or peach.
Some diseases are sex-linked. We specified earlier that you have two copies of each gene, and this is because you have two copies of each chromosome. Well, you do, being a female. You have 46 chromosomes, that's 23 pairs, including a pair of chromosomes called "X".
As a male, I don't. I have 46 chromsomes, 22 pairs of similar ("homologous") chromosomes, plus 1 X and 1 Y. So any gene that lives on the X chromosome, I only have one of. To get back to the first analogy - it's like I inherited a belt from my mother - but no suspenders at all from my father. So if the belt I inherited doesn't work, my pants fall down. There's no suspenders of any kind to hold them up.
Color-blindness is like this. The gene for color-reception (actually, the gene makes proteins your eye cells need to see certain colors) is on the X chromosome. Your father's mother had 2 X chromosomes, and if she wasn't color-blind, we know that she had one "good" gene, and one "broken" gene. Your father got the X chromosome from his mother with the bad gene. From his father, we know he got a Y chromosome - because your father is male - which has no color vision genes at all. So the only gene for that trait he got was the broken one. Hence, he was color-blind.
In your case? How did you get the "weak" version of it? It's a long story. Try to bear with me. We know that you are female, which means you got your father's X chromosome instead of his Y chromosome. And you obviously recieved a normal X from your mother - women only pass on X chromosomes because they don't have Y's. So you're a carrier of the same kind of color-blindness that your father had on one of your chromosomes. Half of you male children can be expected to be color blind. None of your female children will be unless your mate is also color-blind in the same way.
But what about you? How come you have a weakened form of it? Because a human cell only needs one X chromosome to work. It can only allow one chromosome to work. So, when you were a developing zygote, your cells each picked one of the X chromosomes in your cells to "deactivate". They were basically rolled up into balls and tucked away. Not destroyed, so that they could be passed on to your children, but also not a part of that cell's regular genetic activity.
The thing was, each cell at that stage picked at random. Not every cell picked the same X chromosome to mothball. And when each of those cells divided, those "daughter" cells were committed to their parents choice.
The result? Your body is made out of two different kinds of cells - cells that turned off the "bad" X, and cells that turned off the "good" X. They're all mixed up throughout your body, in patches. In your eye, probably what happened is that some of your retina cells - "cones" are normal, and some are color-blind. The reason you only see the effect in low-light or low-saturation conditions is that normally, with bright colors, enough of your normal cones can pick up the slack for your color-blind cones. But when there's not much color in the first place, the deficiency becomes a lot more apparent.
Edited by crashfrog, : No reason given.

This message is a reply to:
 Message 168 by Faith, posted 08-19-2006 1:42 PM Faith has replied

Replies to this message:
 Message 174 by Faith, posted 08-19-2006 3:46 PM crashfrog has replied

ramoss
Member (Idle past 729 days)
Posts: 3228
Joined: 08-11-2004


Message 171 of 218 (341413)
08-19-2006 2:44 PM
Reply to: Message 169 by Faith
08-19-2006 2:26 PM


The reason is that due to the fact that modern jaws are relatively smaller than they were in earlier times. Therefore, the jawbone does not have enough room in many modern jawbones. THis , in turn, causes more dental problems because of crowding.

This message is a reply to:
 Message 169 by Faith, posted 08-19-2006 2:26 PM Faith has not replied

Archer Opteryx
Member (Idle past 3714 days)
Posts: 1811
From: East Asia
Joined: 08-16-2006


Message 172 of 218 (341416)
08-19-2006 3:03 PM
Reply to: Message 169 by Faith
08-19-2006 2:26 PM


Re: Natural Limitation to Evolutionary Processes
Faith asks:
What makes your wisdom teeth mutation "beneficial" in any sense of the word?
No lower wisdom teeth to extract or get impacted? Are you kidding?
I'll take that mutuation any day.

Archer

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 Message 169 by Faith, posted 08-19-2006 2:26 PM Faith has not replied

Faith 
Suspended Member (Idle past 1561 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 173 of 218 (341421)
08-19-2006 3:19 PM
Reply to: Message 165 by nator
08-19-2006 11:23 AM


Far from ignoring the point, this IS the point. Since the defective genes are passed on we have a state of increasing genetic disease in the population.
But if that disease does not hinder reproduction, it doesn't matter with regards to reproductive fitness of the population, as long as the environmental pressures remains the same.
I do have a bad habit of thinking outside the evolution box. I'm trying to get away from the reproductive fitness definition to point out that any disease process that is allowed to accumulate in a population, simply because it escapes the selection processes and does not interfere with reproduction, in itself works against the idea of evolution. This is because it tends to overall reduction in health of that population, which bodes ill for that population's prospects of survival in the long run, let alone the thriving condition one would expect would be required to evolve. The incredible rate of mutation people have referred to here suggests to me that disease factors must be accumulating in all species at the present time. If this had been the case over millions of years, life would simply not exist at all at present.
I would think that for evolution to be possible, mutation would have to be able to produce healthy specimens, but it appears to do a much better job of producing genetic diseases. This is a different problem from the one that inspired me to start this thread in the first place, the fact that the majority of the "processes of evolution" are misnamed, because they are all selective processes that decrease genetic variability. Mutation is the only one that holds any kind of promise of increasing it (recombination merely staves off the inevitable), and this is what we are now discussing, and so far it appears to fail to live up to its billing.
Edited by Faith, : No reason given.
Edited by Faith, : No reason given.

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Replies to this message:
 Message 180 by nator, posted 08-19-2006 6:38 PM Faith has replied
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 Message 202 by Dr Adequate, posted 08-19-2006 10:41 PM Faith has replied

Faith 
Suspended Member (Idle past 1561 days)
Posts: 35298
From: Nevada, USA
Joined: 10-06-2001


Message 174 of 218 (341427)
08-19-2006 3:46 PM
Reply to: Message 170 by crashfrog
08-19-2006 2:27 PM


Thank you, Crash, that is pretty clear and I'm going to keep it for future reference.
Thanks in particular for the discussion of how mutation may cause some maladies by either eliminating the production of a necessary protein or by adding the production of a poisonous one, as it were.
Food for thought.
Edited by Faith, : No reason given.

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crashfrog
Member (Idle past 1584 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 175 of 218 (341429)
08-19-2006 3:53 PM
Reply to: Message 174 by Faith
08-19-2006 3:46 PM


I hope it was helpful. Genetics is a truly fascinating subject.

This message is a reply to:
 Message 174 by Faith, posted 08-19-2006 3:46 PM Faith has not replied

DrJones*
Member
Posts: 2304
From: Edmonton, Alberta, Canada
Joined: 08-19-2004
Member Rating: 4.1


Message 176 of 218 (341441)
08-19-2006 4:41 PM
Reply to: Message 168 by Faith
08-19-2006 1:42 PM


Keratoconus is a fact. (Actually, I just looked it up, and contrary to what DrJones said, the wiki article says it does not lead to blindness.
From the wiki
It does not lead to blindness
Is a bit of an overstatement.
I should clarify, when I say blindness I don't mean no sight at all. In my left eye I've had two cornea transplants reject and my vision is at the worst it'll be in that eye. I can not read the biggest line on the eye chart, when I put my hand out at arms length I can't distinguish my fingers. All I can see out of my left eye is fuzzy blobs of color. I am effectivley blind in the left eye.

Just a monkey in a long line of kings.
If "elitist" just means "not the dumbest motherfucker in the room", I'll be an elitist!
*not an actual doctor

This message is a reply to:
 Message 168 by Faith, posted 08-19-2006 1:42 PM Faith has not replied

Percy
Member
Posts: 22700
From: New Hampshire
Joined: 12-23-2000
Member Rating: 3.7


Message 177 of 218 (341450)
08-19-2006 5:00 PM
Reply to: Message 168 by Faith
08-19-2006 1:42 PM


Faith writes:
OK but it's more than a copout, it's "poisoning the well," that is, making sure that you establish firmly in the reader's mind that Faith doesn't know what she's talking about although you haven't proved it.
Well, yes, of course, that's why I asked your forbearance. I apologize for poisoning the well, but let me address this issue now.
Much of what you're saying takes the form of, "Evolution is wrong because it says such and so," and in many circumstances the actual case is that evolution doesn't say such and so. Anyway, I'll try to be brief.
Here's your original paragraph:
Faith in Message 157 writes:
And what I am saying is that this means that evolution is really impossible, since not only does speciation lead to decreased genetic variability, but the passing on of diseases in the population leads to overall lack of vigor that all by itself tends to extinction rather than to anything that could produce a healthy species as evolution implies must happen.
I'll address it one little bit at a time:
And what I am saying is that this means that evolution is really impossible,...
I think I'll just leave this one alone. You can't really be serious. Was the context intended to provide a number of qualifiers? In other words, was this intended to be interpreted as saying that there are some limited circumstances where evolution is impossible?
...since not only does speciation lead to decreased genetic variability,...
This misunderstands speciation, which occurs at the population level. When a population divides into two separate populations that separately evolve so that they are no longer the same species, this does not allow you to reach any conclusions about genetic variability within the two new species (or maybe one new and one old species, if only one of the populations experiences significant evolution). It can happen in ways that either increase or decrease genetic variability.
So since your assumption that speciation events reduce genetic variation is incorrect, any conclusions you reach based on this assumption are also likely incorrect.
Keep in mind that even in speciation events that do result in reduced genetic variation, the amount of variation can change over time, in either direction.
In other words, saying that speciation events can only reduce genetic variation would be like saying that driving can only carry you closer to home, never further. Just as driving can carry you in either direction with regard to position, so can speciation carry you in any direction with regard to genetic variation. The specific circumstances are what govern in each case.
...but the passing on of diseases in the population leads to overall lack of vigor that all by itself tends to extinction rather than to anything that could produce a healthy species as evolution implies must happen.
The individuals who either experience or inherit the genetic defect are less likely to produce offspring, and any offspring they have that inherit the defect will also be less likely to produce offspring. This means that other members of the population will outproduce them, and it makes it unlikely for unfavorable genes to propagate through a population. Harmful mutations that don't affect reproduction do exist, and they are an interesting story, but they're a side issue.
In other words, for the most part it is rather the exact opposite of what you're claiming that in reality happens. Harmful mutations are filtered from a population because they have anti-survival characteristics. That's what selection does, it picks those with the best set of characteristics for survival. What you're describing is the opposite of selection, and is definitely not a part of evolutionary theory.
As some have explained, disadvantageous mutations can remain present in a population for long periods of time if they are not too harmful. Think of it like the marine motto: Fatal mutations are eliminated right away, the non-fatal take a little longer (perhaps forever).
Addressing this post now...
Faith writes:
Definitely, and this has to be sorted out from defects which are simply passed on "in the wild" because they are not selected out because they do not affect reproduction, which is the situation I think is being discussed here.
Harmful mutations that don't affect reproduction doesn't seem like a fruitful area for this discussion to explore, but I'm not sure yet before I read on in your message. I'll withhold judgment for now.
Are all genetic diseases a matter of the combining of two of the same defective genes?
Crashfrog provided an excellent answer to this already.
But it seems to me we can define this as a defect whether or not it interferes with survival.
Rather than seeking to apply specific labels like favorable gene and unfavorable gene or defect, it would be more accurate to create a list of genetic variables, to each of which we would seek some measure of fecundity. Color blindness would be just another variable. It's importance to survival was likely greater in the past than today.
Well, maybe, but how would you know for sure that this [visual acuity] is a case of natural selection?
Well, maybe it isn't, but are you questioning this because you really doubt that visual acuity provides any survival advantage? Or are you asking this because just in general you doubt that natural selection has any power to affect a population's gene pool, and so you would ask the same question about any example of natural selection.
The point I was making was that if there is a difference in visual acuity generally between primitive societies and civilized societies, then it would likely be due to natural selection. I was just giving a clear and easily understood example illustrating the already very well established and understood principle of natural selection. If you don't accept the principle of natural selection then, while mind boggling, that's a whole other conversation.
And if it's just that you don't believe visual acuity ever provided any selection advantage for human beings, then we'll talk about hawks instead. Visual acuity is a matter of survival for them, and its why theirs is so much better than ours.
I was talking about the proliferation of disease in the population, or general weakness of one sort or another that would NOT affect ability to reproduce -- apart from medical intervention. I think it very likely that overall the entire human population has generally far less strength of various kinds than was the case a few millennia ago.
I wouldn't phrase it this way myself, but I definitely agree with the sentiments. Once human beings developed the ability to compensate for our weaknesses so successfully as to remove us from true competition with other species, and once we developed the ability to treat diseases and coddle and care for the sick and injured and aged, in other words, once we removed ourselves from the forces of natural selection for so many things, naturally the average robustness of the human world population began to decline. And it will continue to decline. I myself would have died a couple of times before reaching reproductive age were it not for modern medicine.
Evolution seems to assume that genetic defects just happen to crop up from time to time at a probably predictable rate -- always and forever, on the uniformitarian principle -- but that we can count on the various selection processes to weed them out.
Just one pet peeve first. Have you ever found any evolution site which describes modern evolutionary theory as uniformitarian? It's a big Internet world out there, I suppose it's not impossible, but in general this is not the way evolutionary scientists would characterize evolution. If you really understand evolution so well that you feel justified at resenting implications that you don't understand it, shouldn't you then at least attempt to understand it using the terms that the field of evolution itself employs? Because I'll tell you, to me, as soon as I see the word "uniformitarianism", it's a big red warning flag that some significant misinterpretation of evolutionary theory is about to be presented.
That being said, yes, genetic mutations occur, in the aggregate, at a predictable rate. Genetic mutations provide the raw material upon which natural selection operates.
Seems to me that as long as some don't interfere with reproduction that over time they would increase in the population and make for a rather sickly bunch...
And here's where you're taking a wrong turn. How could a "rather sickly bunch" reproduce as effectively as a healthy bunch? They couldn't, right? Therefore, the mutations must be having an effect which interferes with reproduction.
In the case of human beings you have to look at the whole picture. If World War III happened tomorrow and sent homo sapiens back to the stone age, I agree that we'd be less successful at surviving than our ancient counterparts. A few generations of no modern medical care would cure this.
But if you compare modern human beings *and* civilization with that of the stone age, we are far and away more successful at reproduction. Just the infant mortality rate alone says so.
--Percy

This message is a reply to:
 Message 168 by Faith, posted 08-19-2006 1:42 PM Faith has not replied

jimfgerard
Inactive Member


Message 178 of 218 (341458)
08-19-2006 5:50 PM


Genetic Science is now aware of quite a few examples of beneficial mutations in extant forms
http://www.gate.net/~rwms/EvoHumBenMutations.html
http://www.gate.net/~rwms/EvoMutations.html
And note these aren't as Creationists often assert created 'only by loss of information'.

democrats are sometimes inept and presently lost but republicans are mean scientifically ignorant hypocrites, I know what lesser of two evils is the most rational choice.

nator
Member (Idle past 2286 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 179 of 218 (341464)
08-19-2006 6:20 PM
Reply to: Message 169 by Faith
08-19-2006 2:26 PM


quote:
What makes your wisdom teeth mutation "beneficial" in any sense of the word?
Well, mostly I think it is a neutral mutation, because wisdom teeth do not emerge until very late in puberty, long after reproduction would have taken place among human populations 100,000 years ago.
No, it could also be viewed as a beneficial mutation if you change the environmental conditions.
Fast forward to a time in human civilization before modern dentistry.
Now imagine impacted wisdom teeth. Very painful, and they often become infected. My mutation removes all chance of impaction, and if I was able to keep reproducing, better teeth for me means better nutrition for my offspring.
quote:
In the case of the mutation that confers immunity to the plague and to HIV, how do you know it is a mutation rather than a normally occurring gene?
Because some people in family groups have the mutation but most people not in those family groups do not.
quote:
That is, perhaps it's the other way around: perhaps the whole human race once had it but mutations killed it and now it survives only in a few.
Why would a beneficial mutation be selected against?
I assume you have now conceded that beneficial mutations do, in fact, exist?
quote:
Sickle Cell is always trotted out. It appears to be a terrific case of One, and a backhanded claim to beneficial mutation since it causes disease simultaneously.
Carriers of SCD rarely have any symptoms.
And you continue to ignore the fact that what the SCD mutation does is to stop people from being killed by maleria before they can reproduce.
All evolution is concerned with is the passing on of genes.
One passes on genes much more successfully if one is alive, destined to die from SCD in one's 40's, compared to if one is dead from malaria at the age of 6 months.
quote:
It's easy to come up with a list of genetic diseases, but notably difficult to come up with any real evidence of beneficial mutations.
Do you or do you not accept that antibiotic resistance in bacteria is "real evidence of beneficial mutations"?

This message is a reply to:
 Message 169 by Faith, posted 08-19-2006 2:26 PM Faith has not replied

nator
Member (Idle past 2286 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 180 of 218 (341471)
08-19-2006 6:38 PM
Reply to: Message 173 by Faith
08-19-2006 3:19 PM


quote:
I'm trying to get away from the reproductive fitness definition to point out that any disease process that is allowed to accumulate in a population, simply because it escapes the selection processes and does not interfere with reproduction, in itself works against the idea of evolution.
No, it really doesn't.
quote:
This is because it tends to overall reduction in health of that population, which bodes ill for that population's prospects of survival in the long run, let alone the thriving condition one would expect would be required to evolve.
What makes you think that evolution requires a species to "survive in the long run"?
Indeed, the history of evolution on Earth is that over 99% of all species have gone extinct.
quote:
The incredible rate of mutation people have referred to here
I am not sure what you refer to here.
What "incredible rate of mutation" do you speak of?
quote:
suggests to me that disease factors must be accumulating in all species at the present time. If this had been the case over millions of years, life would simply not exist at all at present.
But it has has already been explained, most mutations are neutral.
Neutral mutations don't do anything.
quote:
I would think that for evolution to be possible, mutation would have to be able to produce healthy specimens,
It does.
I am healthy, and I have a mutation.
And "healthy" WRT evolution simply means "able to pass on one's genes successfuly."
quote:
but it appears to do a much better job of producing genetic diseases.
Antibiotic resistance in bacteria has produced "superbugs" which are very healthy, wouldn't you say?
quote:
This is a different problem from the one that inspired me to start this thread in the first place, the fact that the majority of the "processes of evolution" are misnamed, because they are all selective processes that decrease genetic variability.
No, they are not.
That this has been explained to you multiple times seems to have done no good at all, so I'm going to leave it to someone else to slog on ahead and try again.
Edited by schrafinator, : No reason given.

"Science is like a blabbermouth who ruins a movie by telling you how it ends! Well I say there are some things we don't want to know! Important things!"
- Ned Flanders
"Question with boldness even the existence of God; because, if there be one, he must more approve of the homage of reason than that of blindfolded fear." - Thomas Jefferson

This message is a reply to:
 Message 173 by Faith, posted 08-19-2006 3:19 PM Faith has replied

Replies to this message:
 Message 198 by Faith, posted 08-19-2006 10:16 PM nator has replied

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