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Author Topic:   Epigenetic Factors as 'Creative' influence in Evolution
Parsimonious_Razor
Inactive Member


Message 1 of 30 (89935)
03-02-2004 11:33 PM


I have recently tried to understand epigenetics beyond simply the idea that nature and nurture form a constant feedback for development of an organism. There is an emergence now of literature that says that epigenetic factors are the primary source of novel adaptations to the environment. It seems to suggest that genetic mutation does not play that much of a role in developing new variation but rather changes in development of the organism.
Assuming the accuracy of these claims bears fruit how significant of a change in evolutionary theory do you think this? The idea that a population has mechanisms to proactively respond to its environment seems to me to alter significantly at least the 'chance' debate of creationist. It seems analogous to the idea that amino acids preference for certain forms alters any of the probability equations for arriving at life significant chains.
Was hoping someone more familiar with these ideas might have some time to kill between real life and ramming the creationist. This place seems an awesome resource.

Replies to this message:
 Message 2 by NosyNed, posted 03-03-2004 12:32 AM Parsimonious_Razor has replied
 Message 5 by Mammuthus, posted 03-03-2004 4:50 AM Parsimonious_Razor has replied
 Message 29 by Brad McFall, posted 03-11-2004 6:32 PM Parsimonious_Razor has not replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 2 of 30 (89938)
03-03-2004 12:32 AM
Reply to: Message 1 by Parsimonious_Razor
03-02-2004 11:33 PM


I sure as heck don't know much about this area. But isn't it possilbe that the epigenetic changes are themselves 'genetic' in that they are heritable. That is, changes in gene expression may be the result of mutations in the control of that expression.
If that is the case how does this change the underlying ideas of the ToE. It just adds yet more complexity to the details of the mechanisms. It also offers paths for relatively small and even single mutations to produce large (somewhat) phenotype changes.

This message is a reply to:
 Message 1 by Parsimonious_Razor, posted 03-02-2004 11:33 PM Parsimonious_Razor has replied

Replies to this message:
 Message 3 by Parsimonious_Razor, posted 03-03-2004 1:11 AM NosyNed has not replied

  
Parsimonious_Razor
Inactive Member


Message 3 of 30 (89943)
03-03-2004 1:11 AM
Reply to: Message 2 by NosyNed
03-03-2004 12:32 AM


Initially this is how I thought epigenetics functioned. Essentially that it was expression of genotypes being turned on or off by cues from the environment or development. It reminded me of work that I was doing with trying to model cellular differentiation as a giant complex of genes turning each other on and off.
But the epigenetic literature seems to be making a much larger claim. Essentially that changes in developmental-behavior can produce novel effects without any prior genetic tendency, and that over time natural selection operates in these new environments and genes are selected for the environment. It seems to be saying that changes to the genome occur because of developmental changes due to environmental changes.
Or slightly differently, that novel behavior or adaptation can occur not because of a genetic mutation or other genetic alteration but a behavioral/developmental change outside of the genome, which can then cause changes in the genome as the organism optimizes to the new environment. It seems to be a proactive change, and separates the genes from the behavior. It certainly respects genes as a powerful force but instead of a one-way arrow from genes to environment it’s placing a two-way arrow.

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Replies to this message:
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Saviourmachine
Member (Idle past 3554 days)
Posts: 113
From: Holland
Joined: 01-16-2004


Message 4 of 30 (89965)
03-03-2004 4:02 AM
Reply to: Message 3 by Parsimonious_Razor
03-03-2004 1:11 AM


I've heard about that genes can turn on in the 'right' environment, a sort of sleeping genes. But that's something different. Why should development selection reflect environment selection?

This message is a reply to:
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Mammuthus
Member (Idle past 6475 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 5 of 30 (89967)
03-03-2004 4:50 AM
Reply to: Message 1 by Parsimonious_Razor
03-02-2004 11:33 PM


quote:
It seems to suggest that genetic mutation does not play that much of a role in developing new variation but rather changes in development of the organism
That would be a bit extreme as much of epigenetic regulation like DNA methylation and histone acetylation are themselves under genetic control and the genes responsible, under selection. Also, epigenetic states are heritable i.e. you express specific maternal or paternal alleles of imprinted genes. There are several hypotheses for the evolution of imprinting including maternal versus paternal conflict.
Here is a really good review article on the subject
Nat Rev Genet. 2003 May;4(5):359-68. Related Articles, Links
What good is genomic imprinting: the function of parent-specific gene expression.
Wilkins JF, Haig D.
Society of Fellows, 7 Divinity Avenue, Harvard University, Cambridge, Massachusetts 02138, USA. jwilkins@cgr.harvard.edu
Parent-specific gene expression (genomic imprinting) is an evolutionary puzzle because it forgoes an important advantage of diploidy--protection against the effects of deleterious recessive mutations. Three hypotheses claim to have found a countervailing selective advantage of parent-specific expression. Imprinting is proposed to have evolved because it enhances evolvability in a changing environment, protects females against the ravages of invasive trophoblast, or because natural selection acts differently on genes of maternal and paternal origin in interactions among kin. The last hypothesis has received the most extensive theoretical development and seems the best supported by the properties of known imprinted genes. However, the hypothesis is yet to provide a compelling explanation for many examples of imprinting.
In any case, you don't need epigenetics to have an effect on development. The environment can alter development in many ways regardless of genetic background i.e. phenocopies or thalidomide for that matter.
Where epigenetics, genetics, and development overlap is a new discpline called evolutionary development which takes into account that genetic variation is only part of the the story of morphological variation as development and environment also have an enormous impact on the final outcome of embryogenesis.

This message is a reply to:
 Message 1 by Parsimonious_Razor, posted 03-02-2004 11:33 PM Parsimonious_Razor has replied

Replies to this message:
 Message 6 by Parsimonious_Razor, posted 03-03-2004 4:52 PM Mammuthus has replied

  
Parsimonious_Razor
Inactive Member


Message 6 of 30 (90111)
03-03-2004 4:52 PM
Reply to: Message 5 by Mammuthus
03-03-2004 4:50 AM


Saviourmachine writes:
I've heard about that genes can turn on in the 'right' environment, a sort of sleeping genes. But that's something different. Why should development selection reflect environment selection?
Genes turning each other on or off, or external proteins triggered by environmental factors regulating binary gene networks is I believe pretty well established. This is still an "in the genes" view of an organisms morphology and behavior and from what I understand would not really be considered an epigenetic factor.
I am not sure I really understand your question though, how would environmental selection NOT reflect developmental selection or vice-versa?
Mammuthus writes:
That would be a bit extreme as much of epigenetic regulation like DNA methylation and histone acetylation are themselves under genetic control and the genes responsible, under selection. Also, epigenetic states are heritable i.e. you express specific maternal or paternal alleles of imprinted genes. There are several hypotheses for the evolution of imprinting including maternal versus paternal conflict.
I agree with this statement but I think epigenetics also talks about more than just regulation directly under control of genes. I think development can be viewed as a sliding scale between factors that are completely under genetic control towards factors that are a mix of the environment and genetics and then factors that are completely under environmental control.
The fact that certain aspects of an organism are totally controlled by genes has been shown, but I would believe most of these are fairly simple process since the more complex a process is the more it needs some level of regulatory control from the environment. A feedback system is defiantly necessary for most "adaptive functions."
The other end of the scale is less researched. Clearly the environment can exact a change on an organism that is not coded at all in its genome but whether the environment can trigger an adaptive reaction that can be selected for with out genes coding for most of the behavior is what I believe is open to debate.
Certain heritable phenomenons that have nothing to do with genes have been produced in fairly simple organisms. Forgive my lack of specifics it’s been a while since I read the study, if necessary I can dig it up again. But essentially researchers grafted the membrane from one single celled organism on to the membrane of a different organism but the same species. The number of cilia on the membrane is usually genetically controlled but in this case the section that was grafted was replicated such that the offspring had the grafted number of cilia and not the genetic number.
This is a basic example and does not generalize well and other examples seem to start bringing up problems of confounding variables. Mice that are handled while young will have grand children that have a higher fear response regardless of rearing. Is this some sort of non-gene passage of behavior or is there a genetic control over the delivery of predation cues to offspring? There are many other similar examples of this behavior both in labs and in the wild.
I think the jury is still out on whether the environment can create these sort of adaptive changes in organisms without a genetic predisposition to the change given the circumstances. But there are a lot of die hard supporters of the idea starting to emerge.
Environment can clearly alter an organism’s development but can this alteration serve as a 'creative' medium for developing adaptive functions? I think this has large ramifications for evolutionary theory since organisms can have some level of proactive adaptation and don't simply have to have a genetic mutation develop to create a new behavior.
My main area of study is biological psychology and evolutionary psychology and many examples that are emerging in this field seem bring up these kinds of questions of development. Several researchers showed that people will often alter the priority they give to physical attractiveness in mate selection in relation to the parasite load of the group they are in. In a somewhat gene dominated view this would be selection between a genetic system that didn’t recognize health cues, a system that recognized health cues regardless of the environment, or a system the recognized health cues in relation to an environmental feedback system. Selection would probably favor the latter and that’s why modern man functions in this way. A more epigenetic view might describe this as people using a genetic predisposition to certain health cues and consciously increasing or decreasing its priority based on what one sees in the group. Instead of genes being responsible for creating the regulation people were able to actively co-opt the process for changing environments.

This message is a reply to:
 Message 5 by Mammuthus, posted 03-03-2004 4:50 AM Mammuthus has replied

Replies to this message:
 Message 7 by Loudmouth, posted 03-03-2004 5:13 PM Parsimonious_Razor has replied
 Message 15 by Mammuthus, posted 03-04-2004 2:57 AM Parsimonious_Razor has replied

  
Loudmouth
Inactive Member


Message 7 of 30 (90115)
03-03-2004 5:13 PM
Reply to: Message 6 by Parsimonious_Razor
03-03-2004 4:52 PM


PR,
Would you say that memes are an epigenetic factor that affect selection, not only in humans but possibly in other organisms (eg, heightened fear in mice)?

This message is a reply to:
 Message 6 by Parsimonious_Razor, posted 03-03-2004 4:52 PM Parsimonious_Razor has replied

Replies to this message:
 Message 8 by Parsimonious_Razor, posted 03-03-2004 6:54 PM Loudmouth has not replied

  
Parsimonious_Razor
Inactive Member


Message 8 of 30 (90141)
03-03-2004 6:54 PM
Reply to: Message 7 by Loudmouth
03-03-2004 5:13 PM


Loudmouth writes:
Would you say that memes are an epigenetic factor that affect selection, not only in humans but possibly in other organisms (eg, heightened fear in mice)?
I think the classification of memes as epigenetic is rooted in how accurate the concepts in epigenetics are. I think the door is still wide open on how much of a role genes can play in thought, behavior and adaptivness of an organism.
From what I understand of memes they are "thought units" that easily gain prominence and have a high likelihood of being "passed on" to other people because they involve concepts that have high adaptive benefit to pay attention too. Mating behaviors and histories, food selection and availability, survival risks whether predatory or pathonogenic, ect. Most modern memes take advantage of these ancestral cues and spread accordingly.
So if this definition is an honest portrayal you are left with the question of whether there is a set of genes that have activated the mind to pay attention to these concepts or if the importance of these concepts was heritable through means other than genes. The proximate cause is almost always going to be environmental, even with a very gene dominated view. The question is, what is the ultimate causation? Was it natural selection acting on genes that regulated thoughts, or was it a non-genetic regulation of thoughts that was beneficial and thus spread. If the former then I think memes are genetic consequences and probably not "epigenetic" if the latter you could even make the case the memes are a form in which epigenetic factors are transmitted across generations or "inherited."
The mice question faces this same dilemma. If there is some gene in the mice that receives a stress hormone from the mother and then stays "on" producing a heightened fear response and as such a stress hormone that activates the genes in their offspring you have a very strongly genetic determinate of behavior and its not really "epigenetic." But if this fear response is passed on without change in the regulation of genes than you have an epigenetic factor. Whether this could be called memetics or not I am not sure, the fear response is not dependent on the rearing environment so it’s not a "cultural" transmission but something involved in embryonic development. In a sense though it could be considered perhaps a more primitive form of the concepts.
I think in general the whole thing is a slight twist on the nature vs. nurture debate. How much of ones behavior do genes really control? But I think what epigenetics brings to the discussion is the idea that even things that exist outside of the genes can be heritable and as such be selected for from evolutionary pressures.

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Replies to this message:
 Message 9 by g_suschaserfreak, posted 03-03-2004 8:42 PM Parsimonious_Razor has not replied
 Message 11 by 1.61803, posted 03-03-2004 10:51 PM Parsimonious_Razor has replied

  
g_suschaserfreak
Inactive Member


Message 9 of 30 (90156)
03-03-2004 8:42 PM
Reply to: Message 8 by Parsimonious_Razor
03-03-2004 6:54 PM


I don't understand what the big deal is, really. Evolutionists(aka the fools) believe in the degradation of human life, and if you go back far enough, we came from ROCKS. Rightfully so, because some of us are so hard headed. But looking at the creationists, who believe in one true God, (these are the wise people) believe we were created by this one true God. Neither can be solidly proven, but I think it would be easier to show how God created me then how you got your rock. It's actually a better choice to believe in God, because he will give you the desires of your heart, otherwise, you'll go to hell. Hmm, a choice between eternal burning flame and suffering, or an eternity with God. Believe in him and you'll get the latter. Even if you're going to die and be gone from existance, don't you think it is worth the risk to believe?

Yes, There is a God. Yes, He love YOU. Yes, this means YOU

This message is a reply to:
 Message 8 by Parsimonious_Razor, posted 03-03-2004 6:54 PM Parsimonious_Razor has not replied

Replies to this message:
 Message 10 by Asgara, posted 03-03-2004 8:48 PM g_suschaserfreak has not replied
 Message 12 by crashfrog, posted 03-03-2004 11:29 PM g_suschaserfreak has not replied

  
Asgara
Member (Idle past 2303 days)
Posts: 1783
From: Wisconsin, USA
Joined: 05-10-2003


Message 10 of 30 (90158)
03-03-2004 8:48 PM
Reply to: Message 9 by g_suschaserfreak
03-03-2004 8:42 PM


Hi there,
This is off topic so I'm only going to give a short response...
Why would anyone want to believe in a god that they think is stupid??
Yeah...It's really going to fool god if you believe just in case...sorry I just can't have any faith in something so easily fooled.
If you really want to discuss this, then I suggest you take it to a thread in faith and belief.

Asgara
"An unexamined life is not worth living" Socrates via Plato

This message is a reply to:
 Message 9 by g_suschaserfreak, posted 03-03-2004 8:42 PM g_suschaserfreak has not replied

  
1.61803
Member (Idle past 1504 days)
Posts: 2928
From: Lone Star State USA
Joined: 02-19-2004


Message 11 of 30 (90170)
03-03-2004 10:51 PM
Reply to: Message 8 by Parsimonious_Razor
03-03-2004 6:54 PM


Nature verse nurture
So behavior can be explained by genes? Interesting.
So can this also predict pathology/psycosis? Or is this still to early to tell?

This message is a reply to:
 Message 8 by Parsimonious_Razor, posted 03-03-2004 6:54 PM Parsimonious_Razor has replied

Replies to this message:
 Message 13 by crashfrog, posted 03-03-2004 11:32 PM 1.61803 has not replied
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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 12 of 30 (90175)
03-03-2004 11:29 PM
Reply to: Message 9 by g_suschaserfreak
03-03-2004 8:42 PM


I don't understand what the big deal is, really.
Yeah, I don't either. On one hand, there's science, which brought you such technologies as medicine and the computer you're reading this on, and then on the other hand, there's religious, superstitious claptrap, which brought us such things as a flat Earth and bleeding as treatment.
Not a hard choice, I guess. How about we get back to the topic, which you don't appear to know anything about?

This message is a reply to:
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crashfrog
Member (Idle past 1467 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 13 of 30 (90177)
03-03-2004 11:32 PM
Reply to: Message 11 by 1.61803
03-03-2004 10:51 PM


So behavior can be explained by genes? Interesting.
I think you missed his point. I think he's saying that behavior isn't just nature or nurture - it isn't even just nature and nurture. It's way more complicated than that.

This message is a reply to:
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Parsimonious_Razor
Inactive Member


Message 14 of 30 (90178)
03-03-2004 11:43 PM
Reply to: Message 11 by 1.61803
03-03-2004 10:51 PM


Re: Nature verse nurture
1.61803 writes:
behavior can be explained by genes? Interesting.
Yes, some behavior is certainly caused primarily by genetics. Others are caused by a mixture between genetic and environmental factors. This is probably the vast majority of behavior. Finally, some behavior maybe caused by environmental effects, I have a hard to time seeing much behavior at all that is caused solely by factors outside the individual. There is behavior in novel environments that appears to be novel behavior, but is probably just some application of a behavior defined in the Environment of Evolutionary Adaptiveness (EEA, which is probably Pleistocene African Savannah for humans).
The question I have is about what defined these EEA behaviors. Is it primarily genetically based and developed through population variation and mutation? Or is there ability for an organism to pass on adaptive strategies to offspring in ways that go beyond genes. At this point I should probably mention that this really isn't a neo-Lamarckian idea. There isn't a transfer of morphology changes due to stressors from parent to fetus. While some information about the environment a fetus is being born into is transferred this is only a small portion. It’s more the idea that behaviors and adaptations in one area could be co-opted in new areas to create new adaptive behaviors without having to wait for genetics to change.
1.61803 writes:
So can this also predict pathology/psychosis? Or is this still to early to tell?
Many pathologies are probably failures of development or genetics. Huntington's chorea is an obvious psychosis caused by genetics. Development and genetics probably mix to create more common problems. The brain, especially during development, is very sensitive to negative influences. It is VERY VERY hard to get the brain to grow right, and any significant deviation from the mean will cause serious issues. Hormonal regulation is probably similar, for example Grave's Disease dumps tons of thyroid into the system and causes all kinds of pathologies. So there is defiantly a genetic factor and environmental factor in most pathologies/psychosis.
What’s interesting is that it is hypothesized that some pathologies have adaptive benefits under some circumstances. For example, psychopaths could have an advantage in social arrangements as long as they are a small portion of the population. Rape is another hot button issue. One of my undergraduate advisors, Dr. Randy Thornhill, hypotheses a rape adaptation in men. It says that under certain circumstances in the EEA men who used sexual coercion for sexual access would have more reproductive success than those who did not. Rape probably dates pretty far back, since most of the great ape family shows a propensity for it. Its most likely a homologous behavior for the hominidaes and dates at least to the ape common ancestor.
Edit: I forgot to add (and couldn't resist) that human pathologies could also be caused by demonic possession, but these are easily cured by consuming mass quantities of beans.
[This message has been edited by Parsimonious_Razor, 03-03-2004]

This message is a reply to:
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Mammuthus
Member (Idle past 6475 days)
Posts: 3085
From: Munich, Germany
Joined: 08-09-2002


Message 15 of 30 (90189)
03-04-2004 2:57 AM
Reply to: Message 6 by Parsimonious_Razor
03-03-2004 4:52 PM


quote:
The other end of the scale is less researched. Clearly the environment can exact a change on an organism that is not coded at all in its genome but whether the environment can trigger an adaptive reaction that can be selected for with out genes coding for most of the behavior is what I believe is open to debate.
Certain heritable phenomenons that have nothing to do with genes have been produced in fairly simple organisms.
Hi PR, I think I am losing the intent of the thread but it is probably my fault. As a molecular biologist, when you say epigenetics it means heritable and mutable DNA methylation patterns, histone acetylation etc. These are subject to mutation like DNA but if you sequenced both an unmethylated and methylated allele of a gene, you would get the same sequence and thus it is "epi"-genetic. That development can be affected in non-heritable ways is clear. If something causes gene expression of a hox gene to be delayed or increase or decrease, this will have an effect on the overall expression gradient of the hox gene which in turn will have an effect on all the genes in expression gradients with which it interacts. So a small change can have an amplified effect. However, this will not be a heritable change. You can however, inherit a methylation pattern from your parents and thus have paternal or maternally imprinted genes like the H19 gene or Igf2r. With development, the genes set out a potential blueprint for development but environment will play almost as much of a role in getting from the gene to the individual...that is why if you cloned a human, the clone may very well not resemble the original behaviorally and would likely be morphologically different.

This message is a reply to:
 Message 6 by Parsimonious_Razor, posted 03-03-2004 4:52 PM Parsimonious_Razor has replied

Replies to this message:
 Message 16 by Parsimonious_Razor, posted 03-04-2004 3:27 AM Mammuthus has replied

  
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