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From: sa209@utb.shv.hb.se (Claes Andersson)
Subject: Re: Lamarckian Evolution
Message-ID: <1995Feb12.154650.7235@gdunix.gd.chalmers.se>
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References: <1995Feb4.043915.6827@gdunix.gd.chalmers.se> <3h47mj$7db@laplace.ee.latrobe.edu.au> <1995Feb8.100831.10995@gdunix.gd.chalmers.se> <3hc1u2$dl0@laplace.ee.latrobe.edu.au>
Date: Sun, 12 Feb 1995 22:06:32 GMT
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khorsell@ee.latrobe.edu.au (Kym Horsell) wrote:
>In article <1995Feb8.100831.10995@gdunix.gd.chalmers.se> sa209@utb.shv.hb.se (Claes Andersson) writes:
>>khorsell@ee.latrobe.edu.au (Kym Horsell) wrote:
>>>In article <1995Feb4.043915.6827@gdunix.gd.chalmers.se> sa209@utb.shv.hb.se (Claes Andersson) writes:
>>>>I don't think you got my point there. Of course germline DNA can be affected
>>>>by genetically defines mechanisms but do you realise the tremendous complexity
>>>>of a genetic re-programmer? It should take a information processor that would
>>>>have to be much more advanced than the brain. We talk about super NP-complete
>>>>problems here! Take a look at the embryology of any species and get a hunch of
>>>>the way genes work, they don't build the body with blocks to say the least!
>>>
>>>You are still arguing along the lines of "I cant see how it would work"
>>>and are also supplying a few (what I shall call) straw men along the way.
>>
>> You are right, I cant see how it would work. The thing is: We know that
>>evolution can come up with tremendous adaptations. BUT we don't know
>>where to stop. A Lamarckistic reprogrammer is something completely else...
>>It's about a numbercruching of an infinit number of factors, It can't be.
>
>OK. Let's see if I can summarise my position more exactly.  (Plus a
>little observational evidence gleaned by others.)
>
>One of the arguments used in science is "I can't find a mechanism".
>In this case that argument, which I would argue is not a very good one
>in any case, can't be easily used.
>
>As I mentioned before Cairn's work on starvation responses in E coli
>are suggestive that Lamarckian mechanisms exist in nature. Simulation
>results from my admittedly over simplistic models suggest that if
>Lamarckian mechs exists they will tend to crowd out non-Lamarck ones
>as per (even) Darwinian theory.  This can be extended to the argument
>that if Lamarckian mechanisms ever arose by "straight mutation" then
>they would tend to dominate "straight Darwin".

 I have a feeling that Cairn uses Lamarckisktic just because the mechanism
have remote simillarities with Lamarckism. I know the E. Coli lactose-
experiment but that isn't any example of how Lamarckism, as Lamarck ment
it works.


>Aside from observation, in order to rule out Lamarck we must be able
>to show with high degree of certaintly there is no way for such
>mechanisms to ARISE. And this, I will argue, is very hard to do
>because some mechanisms are known and/or suggested, if not understood.

No problem. Calculating which DNA-sequence changes, deletions and additions
it would take to affect the delicate embryological growth in a diesired way is
SUPER NP-complete. It's extremely much more complex than cracking the cryptation
of the spy-satellites transmissions but it something like it anyway. You have an
answer and an unknown number of variables. Now calculate those variables!

> - John Cairns
>As I've mentioned, the work of Cairns shows the starvation
>response of certain E coli following Lamarckian lines; and the work
>has been replicated a number of times. Still not infallible, I'll
>grant, but starting to outweight the args against the case for
>Lamarck.
>
>- Pat Foster of Boston U found that the E coli in question took
>advantage of a "double flaw" in the cell DNA. The first "flaw"
>disabled the cell's ability to digest lactose, but after being exposed
>to lactose-only environments a mutant quickly arose that "corrected"
>the reading of the flawed gene during protein synthesis. As I say,
>there are many more ways for "gene editing" to come into the picture
>than simple "environment affects DNA". In this case it was
>"environments affects reading of DNA".
>

 I don't doubt that the envirinment affects the DNA but this has nothing
to do with the design of new sequences. It has to do with that a simple
difference in the cytoplasma can affect the transciption of DNA but it
do in no way CALCULATE how to do it and will always be constrained
to a couple of solutions. What do you think would happen if you encountered
the E. Coli's with something else? Would in "calculate" the appropriate
gene sequences for dealing with other chemicals as well. If it does THAT
would be strange.

>- Barry Hall at U Rochester also confirmed Cairn's results but had an
>explanation. He suggested the idea of "hypermutable" cells that might
>come into play (specifically for Hall) in the starvation
>scenario. This super mutable base would form a pool for a Lamarckain
>mechanism; under certain conditions the appropriate mutations could be
>"encouraged".  Hence such a pool would be modulated by more-or-less
>Darwinian processes to achieve a Lamackian effect. This suggestion has
>some experimental backing.
>
>- Susan Rosenberg of U Alberta have also identified a possible mechanism
>for Lamackian evolution at cellular levels. Cairns and Foster had
>discovered Rec A -- an enzyme crucial in forming the mutation required
>for the "starvation response" -- she and co-workers found Rec
>BCD. Together the enzymes allow one bacterium to swap genes with
>another. The same enzymes also enable DNA repair such as for breaks in
>both DNA strands.  This is one way for a cell to become hypermutable,
>the thinking went. Normal bacterial DNA is circular. If a starving bug
>stops replication in mid-stream and forms a double-strand break the
>Rec enzymes might be able to repair the damage by pulling in pieces of
>DNA from elsewhere in the cell; but in doing the repair a mutation
>might occur. And in a few cases they might be beneficial and allow E
>coli (in that particular case) to regain its ability to digest
>lactose. At that point the bacterium would stop being hypermutable and
>go back to grazing.
>
>The explanation is thought to be neat, but doesn't explain all the
>observations.  For more details read the lit.
>
>---
>
>The above deals with at least some of the observational evidence to
>support a Lamarckain mechanism.
>
>Simple simulations suggest there is an advantage to Lamarck over pure
>Darwin. I have made some slight modifications of the posted program to
>determine adaptation speed and diversity measures for Lamarckian and

 As I've said. I don't doubt it, but as I've also said. It would also be better
to read the solutions instead of solving the mathematics tasks.

>You will also have to admit that DNA is self-describing.  The
>mechanisms that perform protein synthesis are encoded to some
>extent. Hence evolutionary pressures must be factored into
>consideration of such synthesis mechanisms. Is it advantageous to have
>Lamarck come into the picture? I would argue on (just) the basis of
>the simple models I have alluded to above that such is the case. Hence
>Lamarckian mechanisms should appear eventually given only Darwinian
>pressures.  Lamarck can, in a sense, "bootstrap" from
>Darwin. Additionally, multi-celled organisms might also show
>Lamarckian behaviours; again a global Lamarckian effect might
>bootstrap from local effects in the individual cells.

 It is selfdescribing in one respect but still it is recursive, so to find out
one thing you'll have to nst from the beginning, else it will be out of
its context. I also understand in which way you suggest that a Lamarckian
mechanism would appear and I am sure it would, if it would be possible.
But I can assure you, it isn't. I refer to what I've written above.

 Do you suggest that when you stretch your back, the intricate little
effects this has on each cells, a HUGE amount of cells, is interpreted in
such a dynamic way that it can see the difference between when you
stretch your back and when you bend to the left and encode DNA
accordingly. This would be a calcualtion of tremendous size, and you
suggest that there wouldn't have to be any central processing unit
that is visible? If the brain, which can in no way handle such operations
is very noticeable with its great volume, how big is the chance that
somthing of even higher computational power would be microscopic?

Claes Andersson. University of Bors. Sweden



