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Author | Topic: The Koala, Lamark and Epigenetics | |||||||||||||||||||||||||||||||||||||||||||
LamarkNewAge Member (Idle past 738 days) Posts: 2236 Joined: |
The late Farrell Till said that the koala has a very narrow diet; infact some are so specialized that they not only can't eat anything but eucalyptus leaves but they also cannot eat from eucalyptus trees outside their local eucalyptus woods (or something like that).
https://www.youtube.com/watch?v=vnK4dTtX8L0 Could a bunch of random DNA mutations explain the koala diet. I'm asking if the "neo-Darwinian" theory (using Gregor Mendel theory to supplement Darmin's theory) really does best explain this situation. Wouldn't the data suggest that the most logical conclusion is that this narrow diet was acquired by behavior of a koala during his/her life and somehow (by say epigenetic means?) this trait got passed down into succeeding offspring and it got locked into the animals DNA later down the generational tree? Humans used to not be able to digest cow milk until around 6,000 to 10,000 years ago. Now 96% of Sweedish people can digest cow milk. Random DNA mutations brought this about? Perhaps Lamark might have been onto something. Or no? Edited by Admin, : Change title from "Does the narrow quala diet back up Lamark's 1809 theory?" and fix spelling.
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Admin Director Posts: 12998 From: EvC Forum Joined: Member Rating: 2.3 |
Hi LamarkNewAge,
Before I promote your topic (your other topic was promoted to the Coffee House forum and can be found at RationalWiki.org site and Operation Northwoods) I'm going to change the title so that it mentions epigenetics.
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Admin Director Posts: 12998 From: EvC Forum Joined: Member Rating: 2.3 |
Thread copied here from the The Koala, Lamark and Epigenetics thread in the Proposed New Topics forum.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Again, welcome to the fray, LamarkNewAge.
... Wouldn't the data suggest that the most logical conclusion is that this narrow diet was acquired by behavior of a koala during his/her life and somehow (by say epigenetic means?) this trait got passed down into succeeding offspring and it got locked into the animals DNA later down the generational tree? ... My first impression is that modern evolutionary theory is sufficient. There are many example where plants evolve with specific animals\insects\etc to mutual benefit: the plant gets fertilized or seeds distributed in exchange for providing a special diet, and the consumer gets special food in exchange for assisting the plant to grow (fertilizer) and spread.
Could a bunch of random DNA mutations explain the koala diet. I'm asking if the "neo-Darwinian" theory (using Gregor Mendel theory to supplement Darmin's theory) really does best explain this situation.... Yes, because evolution involves selection as well as random variation. What I don't see is a reason to assume a neo-lamarkian explanation, why the data would suggest the diet isolation would be an acquired trait. Can you explain your thinking here? What would be the environmental chemical that would cause this and what would be the source for it? Enjoy Edited by RAZD, : No reason given. Edited by RAZD, : .by our ability to understand Rebel☮American☆Zen☯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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Dr Adequate Member (Idle past 284 days) Posts: 16113 Joined: |
Well, there's the problem of the mechanism. We know that mutation and selection can do the trick, but what exactly are the Lamarckian mechanisms that could do the same thing? You mention epigenetics, but at least in the case of lactase persistence, which you give as your second example, we know that the difference is not epigentic, but genetic (see here). Now, where's the Lamarckian mechanism for producing the appropriate single nucleotide substitutions when required? There isn't one, is there?
P.S: Welcome to the forums.
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LamarkNewAge Member (Idle past 738 days) Posts: 2236 Joined: |
quote: The symbiotic aspect to the koala/eucalyptus relationship can be explained by standard evolutionary theory. I also mentioned the lactose issue. Dr. Adequate linked me to Wikipedia and it had this text on the linked page.
quote: So mammals already have the nearly universal (?) ability to digest milk at birth. "Lactase persistence" is the ability to digest it into adulthood. That issue seems to be an evolutionary adaption tied to a life or death need to get vitamin D in the diet. Mainly a trait brought to Europeans that were isolated in a way that prevented their access to fish, I suppose. Darwinian mechanics do indeed explain this one. Then the next issue.
quote: It seems this quote is the response to the issue of the extraordinary limits in the koala diet. It's a good question you ask and I am not qualified to present the solution. But the problems presented to a neo-Darwinian solution are also quite large. A random mutation (or series of mutations) that lead to such a narrow diet that by coincidence only enables digestion of a single type of plant just doesn't seems to fit what must go on in nature (so my thinking goes anyway). I think of the brain as possibly being similar to a floppy disc where information can be learned in life then passed on to generations. In biology, there seems to be epigenetic inheritance based on stressful experiences during life (such as the loss of hair being passed on to children or belly fat brought on by stress induced cortisol). The issue is how can such dietary-digestion issues come about from 100% random mutations when the loss of such ability doesn't seem to happen in our lives or the lives of the 7 billion people alive today. But perhaps there is a Lamarkian explanation to these things. I don't have the solution though. I'm interested in exploring the problems to Darwinian explanations and the evidence that might back up Lamarkian solutions to other issues and possibly this issue.
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LamarkNewAge Member (Idle past 738 days) Posts: 2236 Joined: |
Bad because the ability was already almost there to start with -even 10,000 years ago.
The issue of the Koala diet however is more complicated.
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RAZD Member (Idle past 1405 days) Posts: 20714 From: the other end of the sidewalk Joined: |
... A random mutation (or series of mutations) that lead to such a narrow diet that by coincidence only enables digestion of a single type of plant just doesn't seems to fit what must go on in nature (so my thinking goes anyway). ... Again you are forgetting selection. Selection is non-random, and it is the other part of evolution that leads to adaptation. I can go into more detail when I get home (my tablet not that friendly to posting linked information). Enjoy PS - type [qs]quotes are easy[/qs] and it becomes:
quotes are easy or type [quote]quotes are easy[/quote] and it becomes:
quote: by our ability to understand Rebel☮American☆Zen☯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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Tanypteryx Member Posts: 4344 From: Oregon, USA Joined: Member Rating: 5.9 |
But perhaps there is a Lamarkian explanation to these things. LamarkNewAge welcome to EvC. We have been studying biology for a couple hundred years at increasingly fine detail. We are at the stage where we observing life at the molecular level and in all that time millions of scientists have not identified any mechanism or effect that we would define as Lamarkian. There have been no discoveries that do not fit with evolutionary theory. Think about it, not one single observation refutes evolutionary theory. If you looked up the biology of koala and eucalyptus I think you will find that it has been studied in exquisite detail and is quite satisfactorily explained without resorting to some unknown undefined mechanism that has escaped notice before.
I'm interested in exploring the problems to Darwinian explanations and the evidence that might back up Lamarkian solutions to other issues and possibly this issue. We have moved far beyond Darwinian explanations today. They are still important, but our understanding has been expanded considerably. Any problems to Darwinian explanations that may have existed have been thoroughly studied and corrected long ago. Can you describe what a Lamarkian solution might be, and how it could have escaped our notice until now? What if Eleanor Roosevelt had wings? -- Monty Python One important characteristic of a theory is that is has survived repeated attempts to falsify it. Contrary to your understanding, all available evidence confirms it. --Subbie If evolution is shown to be false, it will be at the hands of things that are true, not made up. --percy
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NoNukes Inactive Member
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I think of the brain as possibly being similar to a floppy disc where information can be learned in life then passed on to generations. In the case of mammals, there are plenty of more conventional methods for passing along information. Mammals tend to spend time hanging out with mama which means that behavioral information can be passed on by teaching/learning. Assuming a brain is a floppy disk, what part of that disk could possible be passed on genetically or even via epigenetics? What is the mechanism? Under a government which imprisons any unjustly, the true place for a just man is also in prison. Thoreau: Civil Disobedience (1846) History will have to record that the greatest tragedy of this period of social transition was not the strident clamor of the bad people, but the appalling silence of the good people. Martin Luther King If there are no stupid questions, then what kind of questions do stupid people ask? Do they get smart just in time to ask questions? Scott Adams
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LamarkNewAge Member (Idle past 738 days) Posts: 2236 Joined: |
quote: Selection for an animal going blind happens when the animal species will live in a (nearly or)100% dark environment. It takes a lot of molecular energy for eyes to (be able to) see so selection can and does lead to that gene-for-seeing getting turned off in increasingly large numbers of the species over time. But how can 1 million different types of food to possibly eat(represented in an animal by 1 million hypothetical genetic variants) out of 1,000,001 genetic variant possibilities in time get driven out of the gene pool of an animal. I know it CAN HAPPEN according to neo-Darwinian theory but how DOES it happen in practice? Eventually, the molecular mutations won't do what they might be capable of. They can but won't keep on eliminating all the various DNA codes except the one that allows just one (!) type of food to eat. I agree that it might be molecularly efficient and AGAIN I agree that it is genetically possible. (Lamarkian?) Epigenetics is far faster than the lone neo-Darwinian mechanism and might follow a pattern in nature we can picture if we imagine how a chicken learned how to cross the street (it just learned!). How do migratory birds know where to fly (even if their parents weren't around to teach them)? How do we learn anything? Random mutations? We just learn.
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Dr Adequate Member (Idle past 284 days) Posts: 16113 Joined:
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A random mutation (or series of mutations) that lead to such a narrow diet that by coincidence only enables digestion of a single type of plant just doesn't seems to fit what must go on in nature ... Well, again, turning to Wikipedia, I read this:
Koalas are herbivorous, and while most of their diet consists of eucalypt leaves, they can be found in trees of other genera, such as Acacia, Allocasuarina, Callitris, Leptospermum, and Melaleuca. [...] Despite its reputation as a fussy eater, the koala is more generalist than some other marsupial species, such as the greater glider. So using Lamarckism to explain why it only eats a single type of plant is invoking a mechanism that wouldn't work to explain a fact that isn't true. --- As to whether the lactose issue is a good one, I think it's an excellent one because we have the data. We have humans with lactase persistence, and then members of the same species that don't have it, and we have studied the genes of our own species so thoroughly that we know at the nucleotide level exactly what makes the difference. By contrast, the koala is the sole surviving member of its family, its nearest relatives are wombats, and the genome of neither the koala nor the wombat has been sequenced. This leaves the field wide open for speculation about Lamarckian epigenetics and the diet of koalas. Whereas in the case of humans and lactose, we know. It's a test case that we can actually test and not just speculate about. And when we put it to the test it has nothing to do with epigenetics. Edited by Dr Adequate, : No reason given.
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LamarkNewAge Member (Idle past 738 days) Posts: 2236 Joined: |
quote: Well, Lamark didn't have at his disposal knowledge of Gregor Mendel nor many other developments that came out long ago, so a confirmation of raw-Lamark theory wouldn't exactly be expected.
quote:The theory of Erasmus Darwin? Lamark? Or any of the early founders pre-Charles Darwin? Even I wouldn't go that far but I still predict Lamark will carry the day!
quote: The koala and its digestion ability is the extraordinary issue here I am interested in.
quote: I was under the impression that the discovery of epigenetics has been something of a revelation and an ongoing horizon of great scientific intrigue. You are somewhat contradicting yourself in this post.
quote: Perhaps examples of 2 animals with "identical" DNA nevertheless having significant differences with each other through epigenetic expressions can count as somewhat "Lamarkian". I don't know what the best terminology is. This isn't going to be a 100% raw-lamark 1809 solution though (if there even are "Lamarkian" solutions).
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LamarkNewAge Member (Idle past 738 days) Posts: 2236 Joined: |
quote:Mr. Till seemed to suggest that some do have a more limited ability to digest food than others. Not all but some. I wish he was still around so we could email him and ask for specifics. ---
quote: But keep in mind that those who argue for a "Lamarkian" epigenetics suggest that DNA changes come (in time)but only after epigenetics paved the way first. I remember reading a Seed Magazine (a subscription I had in 2006 to a scientific publication and I'm not even sure if it is still around) from 2006 (?) where they made a good case. The lactose variations were already were very present in the human genetic code. I was drawing an analogy that wasn't the best one.
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Dr Adequate Member (Idle past 284 days) Posts: 16113 Joined:
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(Lamarkian?) Epigenetics is far faster than the lone neo-Darwinian mechanism ... But an epigenetic hypothesis only defers the Darwinian question. Epigenetic Lamarckism works like this, as I understand it. You have, external to the DNA, a switch, a toggle, affecting DNA expression. The position of the switch is inherited, but can be flipped as a response to the environment. So, let's imagine an epigenetic explanation for the koala diet. What we would need is some sort of switch that toggles between eating like a wombat and eating like a koala, which is flipped into koala mode by some exterior stimulus such as, I dunno, smelling eucalyptus. OK, we now have a nice simple explanation for how and why koalas eat eucalyptus. But we have also saddled ourselves with rather difficult problem: how did the two dietary options and the switch between them evolve? So we haven't really made things any simpler. --- Imagine an alien who thinks that humans are stupid. So when he finds a bicycle, he declares that it's way too sophisticated to have been designed and built by humans unaided. No, he explains, it must have been designed and built by some sort of industrial robot, and all the poor dumb humans did was perform the relatively simple task of pushing the big red ON button on the front of the robot --- and pushing buttons, he smugly explains, is well within their primitive capacities ... Well, he hasn't made things any easier for himself, has he? Because now he needs to explain how those dumb humans who're too stupid to build a mere bicycle managed to produce the robot. Edited by Dr Adequate, : No reason given.
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