Register | Sign In


Understanding through Discussion


EvC Forum active members: 53 (9179 total)
3 online now:
Newest Member: Jorge Parker
Upcoming Birthdays: Theodoric
Post Volume: Total: 918,133 Year: 5,390/9,624 Month: 415/323 Week: 55/204 Day: 31/24 Hour: 3/5


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Natural Limitation to Evolutionary Processes (2/14/05)
nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 163 of 299 (341347)
08-19-2006 11:10 AM
Reply to: Message 146 by Faith
08-18-2006 1:00 PM


quote:
The problem is that most changes by mistake are not desirable ones.
Most genetic changes by mistake are neutral with regards to fitness, actually.
quote:
"Genetic difference" in itself is not at all desirable in other words. This is how we get all the genetic diseases.
This is also how we get genetic benefits.
Bacteria obtain antibiotic resistance in exactly this way, which would certainly be a benefit to the bacteria, right?

"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 146 by Faith, posted 08-18-2006 1:00 PM Faith has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 165 of 299 (341351)
08-19-2006 11:23 AM
Reply to: Message 157 by Faith
08-19-2006 3:02 AM


quote:
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.

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 173 by Faith, posted 08-19-2006 3:19 PM nator has replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 166 of 299 (341361)
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 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 167 of 299 (341369)
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

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 179 of 299 (341465)
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

Replies to this message:
 Message 253 by Archer Opteryx, posted 08-21-2006 3:02 PM nator has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 180 of 299 (341470)
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

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 181 of 299 (341474)
08-19-2006 6:47 PM
Reply to: Message 168 by Faith
08-19-2006 1:42 PM


quote:
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.
Did you read my wiki on Sickle Cell?
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.
Edited by schrafinator, : 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 184 by Faith, posted 08-19-2006 8:39 PM nator has replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 189 of 299 (341526)
08-19-2006 9:25 PM
Reply to: Message 184 by Faith
08-19-2006 8:39 PM


quote:
And what would be the specifically GENETIC reason for this breeding out of the defective gene? As the wiki article says it is Autosomal Recessive, which means its transmission follows pretty standard inheritance patterns quite apart from the environmental situation.
There is no selection pressure in favor in the US since there is no endemic malaria here.
There is selection pressure against it because people who get two copies of the mutation tend to have lower reproductive success.
On balance of these two selection pressures, the incidence of SCD would tend to decrease withing the population.
quote:
Would it be silly of me to point out that African Americans are a mixture from all kinds of genetic sources, a lot of European slave-owner in the mix for one thing, so that there is likely to be a lot fewer sickle cell carriers in the overall population than in West Africa for THAT reason?
Sure, that is certainly a possibility, although this does not explain why the incidence is declining in the US.

"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 184 by Faith, posted 08-19-2006 8:39 PM Faith has replied

Replies to this message:
 Message 192 by Faith, posted 08-19-2006 9:46 PM nator has replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 190 of 299 (341531)
08-19-2006 9:29 PM
Reply to: Message 188 by Faith
08-19-2006 9:25 PM


Re: Working against evolution? I'm afraid not.
quote:
I'm not saying they are not beneficial according to evolution's definitions,
Then you agree that beneficial mutations exist.
quote:
I'm saying they are a pretty pathetic offering in defense of the claim of massive beneficial mutations, in light of the known long list of destructive mutations.
You are willfully ignoring everything everyone has said to you in this thread.
You are simply repeating your initial objections without having addressed the vast majority of the points people have raised.

"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 188 by Faith, posted 08-19-2006 9:25 PM Faith has replied

Replies to this message:
 Message 195 by Faith, posted 08-19-2006 9:51 PM nator has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 191 of 299 (341533)
08-19-2006 9:34 PM


why Sickle Cell Disease is "cool"
The real reason SCD is so interesting within the Evolutionary framework is that it is such a great example of how the ToE can explain this seeming paradox of why a genetic disease would be retained within a population.

"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

Replies to this message:
 Message 193 by Faith, posted 08-19-2006 9:49 PM nator has replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 194 of 299 (341544)
08-19-2006 9:51 PM
Reply to: Message 192 by Faith
08-19-2006 9:46 PM


quote:
Fine, the lack of malaria means more without the sickle cell survive in the US. Sorry, I posted too fast.
No problem, we all do that.
quote:
But the genetic dilution certainly DOES contribute to the declining incidence of sickle cell. It means there are fewer sickle cell genes in the overall population, so that the incidence of their pairing up is reduced. Unless you are claiming that Europeans carry the same gene.
SCD in the "overall population" was never under discussion.
Again, from the wiki:
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.

This message is a reply to:
 Message 192 by Faith, posted 08-19-2006 9:46 PM Faith has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 197 of 299 (341549)
08-19-2006 9:58 PM
Reply to: Message 193 by Faith
08-19-2006 9:49 PM


Re: why Sickle Cell Disease is "cool"
The real reason SCD is so interesting within the Evolutionary framework is that it is such a great example of how the ToE can explain this seeming paradox of why a genetic disease would be retained within a population.
quote:
A completely irrelevant point it seems to me. It's rare to the point of singularity for one thing, and as such it's wasting this thread.
Not irrelevant, on at least these two points:
1) your claim that there are no beneficial mutations is refuted.
2) your claim that the retention of genetic diseases in a population runs counter to the ToE has been refuted.
quote:
All it takes for a genetic disease to be retained within a population is that the victim of it survive to reproduce.
Not quite.
It also needs to confer a reproductive advantage to remin prevalent in a population.
That's why SCD continues to flourish in places where malaria is endemic, and also why it is tending to decline in the US among populations with recent ancestry in places where SCD confers reproductive advantage.
Edited by schrafinator, : kan't spel

"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 193 by Faith, posted 08-19-2006 9:49 PM Faith has replied

Replies to this message:
 Message 199 by Faith, posted 08-19-2006 10:20 PM nator has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 201 of 299 (341565)
08-19-2006 10:28 PM
Reply to: Message 198 by Faith
08-19-2006 10:16 PM


Faith, you are begining to become belligerant.
You are simply repeating your initial assertions and willfully ignoring or selectively misinterpreting what everyone has been trying to say to you.
Intelligent, productive conversation is impossible with one such as you, since you refuse to learn or. All you do is project personal incredulity in place of rational argument while twisting what everyone tries to tell you about science.
The same thing has happened in every thread you attempt in the science fora.
Perhaps it really isn't "everybody else" who refuses to accept your obvious brilliant understanding of Evolution and the scientific method, but your own inability to debate the issues in good faith.

"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 198 by Faith, posted 08-19-2006 10:16 PM Faith has replied

Replies to this message:
 Message 207 by Faith, posted 08-19-2006 10:53 PM nator has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 214 of 299 (341616)
08-20-2006 12:02 AM
Reply to: Message 212 by Faith
08-19-2006 11:23 PM


quote:
Find the post yourself. I don't care what you do with it. The thread is a disaster now with so many chiming in to remind me of things I've already answered. Yes answered. Nobody wants to think, you just want to regurgitate evo assumptions. Trash it all the way to the end now. Have the usual evo self-congratulatory blast.
And this is why you should probalby not venture into the science fora, faith.
You have a stroke any time your ideas are treated just like we would treat each others'.
You do not appear to be listening.
You appear to be repeating your initial claims and redefining terms and words into your own special meanings as fast as can be to keep up with all of the demolition of your objections.
You may flail and shout and exasperate all you want, but it is simply not the case that you have adequately addressed any of the responses to your claims.
If you can't take the heat of scientific inquiry, then maybe you should stay out of the Biology lecture hall, so to speak.

"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 212 by Faith, posted 08-19-2006 11:23 PM Faith has not replied

nator
Member (Idle past 2279 days)
Posts: 12961
From: Ann Arbor
Joined: 12-09-2001


Message 238 of 299 (341867)
08-21-2006 8:05 AM
Reply to: Message 229 by Faith
08-20-2006 4:11 PM


wisdom teeth wisdom
quote:
The wisdom tooth example cannot possibly be taken seriously as a beneficial mutation, or even a neutral mutation since it has a definite effect in eliminating wisdom teeth. It gets all philosophically confused to try to figure out how the absence of such teeth MIGHT conceivably confer a benefit.
I don't need my wisdom teeth for survival, nor for reproduction.
Indeed, many, many people don't have room in their jaws for wisdom teeth (why is this so often the case, do you think? And don't say "the Fall". That's a cop out.) and it causes all sorts of pain and impaction and infection. Many, many people have to have these four teeth completely removed because they cause so much trouble. Without modern dentistry, those people would be SOL, wouldn't they?
I never had to worry about any of that because the teeth just don't exist, thanks to my mutation.
quote:
It seems to me that if it involves the destruction of a gene, that ought to be the defining factor, and I can't see such destruction as a positive in any sense whatever.
You seem to be saying that any destruction of a gene must be considered detrimental.
Well, what if a mutation caused the destruction of a disease-causing gene?
Would you consider that to be detrimental and negative?
And I also think you are harboring another misconception about what happens in this particular mutation.
You keep using the word "destruction", but you should more accurately be using the word "change".
This mutation is is a change in the nuceotide sequence. No genes have been lost (although that can happen, just as additions can also happen). I just have a different nucleotide sequence in that particular gene than someone who has all of their wisdom teeth.
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 229 by Faith, posted 08-20-2006 4:11 PM Faith has replied

Replies to this message:
 Message 266 by Faith, posted 08-21-2006 9:41 PM nator has replied

Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024