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Author Topic:   Precedence of Phenotype or Genotype in the evolution of 'novel' traits.
Wounded King
Member (Idle past 2171 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 1 of 13 (457928)
02-26-2008 11:44 AM


In the Re-Theory of Evolution thread, Bluejay and Bertvan have been discussing whether genetic changes precede or follow phenotypic changes.

Bertvan stated that ...

Bertvan writes:

My own view is that the ability to make intelligent, purposeful responses is an observable trait of all living systems. Even single cells are capable of some limited creative response to environmental stimuli. Such responses are heritable, epigenetically, as traits develop, and only become encoded into the genome if persistent over generations

The last part of this sounds quite like a real phenomenon, that of genetic assimilation. Genetic assimilation involves environmental effects giving rise to particular phenotypes which can then become genetically 'fixed' as it were so the environmental stimulus is no longer required.

The problem is that there is no evidence this is in any way connected to any 'creative response'. Phenotypic responses to the environment are still mediated by the interaction of the organisms genome with its environment. There is nowhere else for the 'responses' Bertvan posits to come from.

There is certainly no evidence that such 'responses' are purposeful or guided by any form of intelligence.

Bluejay countered ...

Bluejay writes:

be careful with this, because phenotypic changes don't usually happen without genotypic changes happening first.

There is certainly plenty of empirical evidence from hundreds of mutational studies to support this, although it does not perhaps give the neccessary credence to the idea that instances where phenotypic change has preceded genotypic change (in some sense at least) may still have considerable significance.

These arguments raise these questions to my mind ...

Is there a coherent argument to be made for any sort of entirely genetically independent epigenetic inheritance becoming genetically encoded over generations?

Is there any reason to suppose that such a mechanism would in any way require intelligence to operate?

Is too much emphasis put on purely genetic changes and not on the long term interactions between the genotype and the environment?

TTFN,

WK


Replies to this message:
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Adminnemooseus
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Posts: 3879
Joined: 09-26-2002


Message 2 of 13 (458010)
02-26-2008 8:13 PM
Reply to: Message 1 by Wounded King
02-26-2008 11:44 AM


"Intelligent Design" or "Biological Evolution" forum?
Seems like it could go either direction. I'm leaning the "Biological Evolution" direction.

Opinion and perhaps a little explanation behind your opinion?

Adminnemooseus


This message is a reply to:
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Wounded King
Member (Idle past 2171 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 3 of 13 (458072)
02-27-2008 4:21 AM
Reply to: Message 2 by Adminnemooseus
02-26-2008 8:13 PM


Re: "Intelligent Design" or "Biological Evolution" forum?
It's a bit of a toss up. Definitely the basic framing of the question is in terms of 'simple' biological evolution, but Bertvan's ideas, which I would like to discuss, are definitely firmly ID.

I'd go with your instinct and put it into 'Biological Evolution'. The ID aspect is not the primary one and Bertvan already has his own PNT on some of his ideas on 'intelligence' and the immaterial.

TTFN,

WK


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Adminnemooseus
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Message 4 of 13 (458230)
02-27-2008 7:45 PM


Thread moved here from the Proposed New Topics forum.
    
RAZD
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Posts: 19756
From: the other end of the sidewalk
Joined: 03-14-2004
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Message 5 of 13 (458239)
02-27-2008 9:54 PM
Reply to: Message 1 by Wounded King
02-26-2008 11:44 AM


Is there a coherent argument to be made for any sort of entirely genetically independent epigenetic inheritance becoming genetically encoded over generations?

My understanding is that chemicals (hormones to pollutants) can change the way specific organisms exposed to them develop and mature into adult organisms capable of reproduction. Such developmental traits would be inheritable as long as the chemical exposure lasts. Mutations can then occur that have the same effect without the chemical exposure, possibly by disabling development that would occur without the chemicals.

An example of an environmental effect is the different heat during development that changes sex in alligators. Another example is that selecting for different adrenaline levels in russian farm foxes results in "domestic breed" traits in foxes similar to dog traits.

It seems to me that this would have to be a process where a number of different mutations would have the same effect.

The problem is that there is no evidence this is in any way connected to any 'creative response'.

To be a "creative response" - ie intentional - you would have different possible responses to the same stimulus from otherwise identical organisms, all of which would be beneficial.

This obviously does not occur.

Is too much emphasis put on purely genetic changes and not on the long term interactions between the genotype and the environment?

Yes.

Enjoy.


we are limited in our ability to understand
by our ability to understand
RebelAAmericanOZen[Deist
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This message is a reply to:
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Blue Jay
Member (Idle past 774 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 6 of 13 (458263)
02-28-2008 12:46 AM
Reply to: Message 1 by Wounded King
02-26-2008 11:44 AM


Wounded King writes:

Is there a coherent argument to be made for any sort of entirely genetically independent epigenetic inheritance becoming genetically encoded over generations?

Although I've never looked into this, I would hypothesize epigenetics (in the form of imprinting) as a mechanism behind the atrophy of vestigial organs. I guess this wouldn't really have to become genetically-encoded, though.

Also, here in the western US (and perhaps other places) I have seen a lot of bright blue pillbugs. I did some personal "research" on it, and found a website where a man identified the causal mechanism of the blueness as a virus which had become so prevalent as to create a crystalline network that strongly reflected blue light.

That got me thinking: here at BYU, everything's blue (school colors, you know), so this blue coloration could be advantageous (even though it shortens lifespan considerably). Now, this blue is due to structural coloration, not pigments, so it's not likely to become encoded. But, if it were pigmentation (or otherwise encodable), viral transformation could pass it to the host.

I wish I knew a better example than this, because this one's kind of a stretch.


Signed,
Nobody Important (just Bluejay)
This message is a reply to:
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Blue Jay
Member (Idle past 774 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 7 of 13 (458266)
02-28-2008 12:57 AM
Reply to: Message 5 by RAZD
02-27-2008 9:54 PM


Adaptive Radiation
RAZD writes:

To be a "creative response" - ie intentional - you would have different possible responses to the same stimulus from otherwise identical organisms, all of which would be beneficial.

This obviously does not occur.

I disagree with this. I think adaptive radiation results from responding differently to the same environment. Although, this may be because they are responding to different cues in that given environment.

But, when pomace flies (genus Drosophila) reached Hawaii, they quickly filled every niche available for herbivorous flies, by each electing to follow a different pattern of food consumption (among other factors).

So, I think there may be something to bertvan's idea. However, I think it leads toward natural selection more than toward intelligent design.

Edited by Bluejay, : Grammar


Signed,
Nobody Important (just Bluejay)
This message is a reply to:
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Wounded King
Member (Idle past 2171 days)
Posts: 4149
From: Edinburgh, Scotland
Joined: 04-09-2003


Message 8 of 13 (458306)
02-28-2008 9:24 AM
Reply to: Message 7 by Blue Jay
02-28-2008 12:57 AM


Re: Adaptive Radiation
I disagree with this. I think adaptive radiation results from responding differently to the same environment. Although, this may be because they are responding to different cues in that given environment.

But what is the basis of this differential response? I think that RAZD's point is that we would expect genetically identical organisms to respond in the same way to identical environments and that the spectrum of mutation we would expect to see would still be random, not directed towards particular beneficial responses to environmental challenges.

Surely the basis of the different responses to environmental 'cues' is going to be in genetic variation in the population, and that variation means that the organisms are not identical.

I think RAZD's hypothetical refers to something like an experiment where antibiotics are added to a culture and in the next generation there are several independent mutations all beneficial to the bacteria in terms of survival in an antibiotic environment, i.e. all the bacteria got their little bacterial thinking caps on and came up with different novel strategies for coping. The most important distinction between such a scenario and what actually happens, apart from the caps, is that in generations after the antibiotic is added, provided it is not immediately lethal there will be a wide spectrum of both beneficial and detrimental mutations, one might argue of course that a 'creative response' could also include detrimental mutations.

The situation needs framed differently of course when you add a stricter bacteriocidal immediately lethal antibiotic regime to a grown culture, in that case you are principally looking for pre-existing genetic variation providing differential survivability, in which case you would have to think of the 'creative response' as pre-emptive.

TTFN,

WK


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Modulous
Member (Idle past 180 days)
Posts: 7789
From: Manchester, UK
Joined: 05-01-2005


Message 9 of 13 (458308)
02-28-2008 9:32 AM
Reply to: Message 1 by Wounded King
02-26-2008 11:44 AM


Is there a coherent argument to be made for any sort of entirely genetically independent epigenetic inheritance becoming genetically encoded over generations?

Would it be worth exploring some kind of Baldwin effect?. It's not entirely genetically independent I know but it's the closest I can think of.


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Blue Jay
Member (Idle past 774 days)
Posts: 2843
From: You couldn't pronounce it with your mouthparts
Joined: 02-04-2008


Message 10 of 13 (458343)
02-28-2008 2:03 PM
Reply to: Message 8 by Wounded King
02-28-2008 9:24 AM


Re: Adaptive Radiation
Wounded King writes:

But what is the basis of this differential response?

I guess I was thinking more along the lines of learned behaviors or resource-exploitation. A plethora of dietary specialists could certainly come from a single, generalist stock based on intraspecies competition.

Wounded King writes:

I think that RAZD's point is that we would expect genetically identical organisms to respond in the same way to identical environments...

I understood bertvan's original idea to be a challenge to this viewpoint, though: that the basis of an organism's behavior is spontaneous (or volitional) and not deterministic.

Check this out: Maye, Hsieh, Sugihara and Brembs (2007). Order in Spontaneous Behavior. PLoS ONE 2(5): e443

This article shows that fruit flies tend to follow a structured flight pattern, even when outside stimuli are not provided. FOXNews has called this "free will," but this paper doesn't actually do much to refute the idea that identical organisms will respond to the environment in the same way. Read Brembs' quotes from the last section of the FOXNews article called "condition for free will."

I'm not sure this is what you're getting at, though.


Signed,
Nobody Important (just Bluejay)
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Brad McFall
Member (Idle past 3109 days)
Posts: 3428
From: Ithaca,NY, USA
Joined: 12-20-2001


Message 11 of 13 (458440)
02-28-2008 9:47 PM
Reply to: Message 1 by Wounded King
02-26-2008 11:44 AM


At the end of Harrison’s talk he fielded a question (that apparently Harrison and Provine had discussed might be asked while they walked over to the Art’s quad immediately before the talk)on this topic.

Someone was linking Lamarck (as against what Harrison had lectured as the core principles of Darwinism (not really any different than Gould has in his last large book on the Structure of Evolutionary Theory)) and epigenetics, with the question as to if there was really anything in that field of worthwhile size to consider. Harrison begged off, admitting that there might be something with DNA methylation. He did not however actually suggest how this was to be thought in the whole organism terms he had been presenting.

I recall that we had started to talk about this before on EVC at
http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=5&t=526&m=46
but we also have more recently the thread
http://www.evcforum.net/cgi-bin/dm.cgi?action=msg&f=5&t=799&m=12

I have not had the time, again, to work out my own full thoughts on this specific topic as I present in these notes below


Click to enlarge
but above I make a statement about "seperate creation" which must apply directly to the question you pose here. I will try to give it more thought.
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Explorer
Junior Member (Idle past 3945 days)
Posts: 24
From: Sweden
Joined: 02-24-2008


Message 12 of 13 (458483)
02-29-2008 8:58 AM


I shall add something that I believe fits in this thread. A note from Sweden ;)

"Transmission of Stress-Induced Learning Impairment and Associated Brain Gene Expression from Parents to Offspring in Chickens"

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1838921


Our results suggest that, in WL the gene expression response to stress, as well as some behavioural stress responses, were transmitted across generations. The ability to transmit epigenetic information and behaviour modifications between generations may therefore have been favoured by domestication. The mechanisms involved remain to be investigated; epigenetic modifications could either have been inherited or acquired de novo in the specific egg environment. In both cases, this would offer a novel explanation to rapid evolutionary adaptation of a population.

I am not qualified at this moment to speculate about these things so I let others do that and will comment later.


    
RAZD
Member
Posts: 19756
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.5


Message 13 of 13 (458576)
02-29-2008 10:56 PM
Reply to: Message 7 by Blue Jay
02-28-2008 12:57 AM


Re: Adaptive Radiation
I think adaptive radiation results from responding differently to the same environment.

I think WoundedKnight answered most of this, but just want to point out that what I was positing was not different results from slightly different organisms, but actually identical organisms, would have to be able to react (phenotype) in a multiplicity of ways to the same stimulus, all beneficial (for bertvan's idea to be valid).

But, when pomace flies (genus Drosophila) reached Hawaii,

Existing population full of diversity, not clonal. I was trying to eliminate this variable from the thought experiment.

Enjoy.


we are limited in our ability to understand
by our ability to understand
RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.


• • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •

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