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Author Topic:   The Koala, Lamark and Epigenetics
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 5 of 43 (774885)
12-24-2015 10:03 AM
Reply to: Message 1 by LamarkNewAge
12-24-2015 8:42 AM


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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 Message 1 by LamarkNewAge, posted 12-24-2015 8:42 AM LamarkNewAge has replied

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Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 12 of 43 (774895)
12-24-2015 1:06 PM
Reply to: Message 6 by LamarkNewAge
12-24-2015 11:08 AM


Re: Perhaps the lactose issue wasn't a good one.
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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 Message 6 by LamarkNewAge, posted 12-24-2015 11:08 AM LamarkNewAge has replied

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Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 15 of 43 (774898)
12-24-2015 1:32 PM
Reply to: Message 11 by LamarkNewAge
12-24-2015 1:03 PM


Re: Perhaps the lactose issue wasn't a good one.
(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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 Message 11 by LamarkNewAge, posted 12-24-2015 1:03 PM LamarkNewAge has replied

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 Message 18 by LamarkNewAge, posted 12-24-2015 1:46 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 17 of 43 (774901)
12-24-2015 1:38 PM
Reply to: Message 16 by LamarkNewAge
12-24-2015 1:35 PM


Re: Perhaps the lactose issue wasn't a good one.
Will we still be saying that 100 years from now?
As we won't be alive 100 years from now, I suggest that what we should do in the present is affirm those views that are best supported by the data we've actually got.

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 Message 16 by LamarkNewAge, posted 12-24-2015 1:35 PM LamarkNewAge has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 28 of 43 (774917)
12-24-2015 8:11 PM
Reply to: Message 18 by LamarkNewAge
12-24-2015 1:46 PM


Re: Perhaps the lactose issue wasn't a good one.
I was thinking something more along the lines of the animals choosing to eat a narrow diet for like 7000 years(while still having the ability to digest thousands of things) but eventually loosing the ability to digest the other things at the end of the (say) 7000 year period.
Well, it would involve not just a loss but a gain, since eucalyptus leaves are toxic to most animals --- wombats couldn't eat them even if they could climb trees. So what you need is an epigenetic system where the switches for "eat grass" and "eat roots" and "eat sedge" and so on get switched to OFF, while a pre-existing switch for "be able to eat eucalyptus without dying" gets switched to ON.
Well, my point is that it's not simpler to postulate the evolution of this array of options and switches, and then the switches being flipped, than it is to postulate an ordinary Darwinian mechanism for wombats evolving to eat eucalyptus. But greater simplicity was, so far as I can see, your only reason for postulating epigenetic mechanisms in the first place.

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 Message 18 by LamarkNewAge, posted 12-24-2015 1:46 PM LamarkNewAge has replied

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 Message 29 by LamarkNewAge, posted 12-24-2015 8:47 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 30 of 43 (774920)
12-24-2015 9:24 PM
Reply to: Message 29 by LamarkNewAge
12-24-2015 8:47 PM


Re: You noticed my weak responce. lol
I just never expected that there would be such decent evidence coming in from the scientific side. Honestly, I was just amazed almost 10 years ago when I saw that Seed article. Previously, I automatically wrote off, in my mind, any slight look at "new age" type of evidence. I just didn't think it would get 1 second of coverage by serious scientists though I felt it should.
Well, I don't think anyone now doubts that there are epigenetic effects which could be loosely described as Lamarckian. But that doesn't give us warrant to point to a particular thing (like the koala diet) and say that in that case it's Lamarckian --- not without some sort of positive evidence of an epigenetic mechanism. Nor does it particularly strengthen the case for the inheritance of complex memories --- just because that would be Lamarckian, and Lamarckian things happen, that's not a particularly good reason to believe in it; just as the existence of green objects is not a terribly good reason to believe in green giraffes.

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 Message 29 by LamarkNewAge, posted 12-24-2015 8:47 PM LamarkNewAge has replied

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 Message 31 by LamarkNewAge, posted 12-24-2015 9:56 PM Dr Adequate has replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


(1)
Message 32 of 43 (774924)
12-24-2015 10:44 PM
Reply to: Message 31 by LamarkNewAge
12-24-2015 9:56 PM


Octopods
I was amazed when a friend told me that she worked for an organization that actually trained Octopi to disarm bombs. I was shocked that an animal with no "brain" could do such a thing.
But an octopus does have a brain, and quite a large one for its size. I read here:
The typical adult octopus has a relatively large brain, estimated at 300 million neurons. The ratio of octopus brain to body mass is much higher than that of most fish and amphibians, a ratio more similar to that of birds and mammals.
Edited by Dr Adequate, : No reason given.

This message is a reply to:
 Message 31 by LamarkNewAge, posted 12-24-2015 9:56 PM LamarkNewAge has not replied

  
Dr Adequate
Member (Idle past 284 days)
Posts: 16113
Joined: 07-20-2006


Message 38 of 43 (775141)
12-28-2015 9:21 PM


Epigenetics Does Not A Revolution Make
Article here.
I don't know how much of it you'll find interesting. Here's a good quote:
If quasi-Lamarckian heritable epigenetic patterns within the genome were so powerful and ubiquitous as to overturn a Mendelian understanding of heritability, then the Mendelian model of inheritance would not have been so persuasive and crystal clear in the first place.

  
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