Motorcycle Mama

Got lost in the above. If Lamarckian acquired attributes are the result of environmental stress and those attributes are then inherited if both parents acquire the same ones then how does one decouple the environment and Lamarck's inheritance?

What part of Lamarck was wrong, the internal drive towards increasing complexity or the incorporation followed by the inheritance of acquired attributes? Who tested them? I know people cut tails off rats and the parents never produced tailess offspring but that's not what Lamarck talked about. I also know about Wiseman (I believe he's the one) who argued for the separation of soma and germ but that applies only to a animals and the germ lines share nerves, blood and lymph with the rest of the body. Also a book by Eva Jablonka and ??? Lamb (a computer search under the first author should find it) on Lamarckian evolution; the evidence is accruing.
MM

Xixax

No, that doesn't follow. That would be the case if you claimed that Natural Selection was the only filter for mutation, but not if it is one of many. The rest of that point falls on that basis.

The other two I'll leave to others to talk about.

Natural Selection alone isn't capable of explaining the entire mechanism of evolution. That isn't something new to anyone, nor anything anyone actually thinks is true.

Xixax

btw, the apology is accepted and appreciated. This may very well be the first time I can recall someone actually doing that.

Jack the Bodiless

Why should he? "Goddidit" is always a possibility (assuming a God who works in very mysterious and roundabout ways), but it's not a useful explanation. If there is another answer that works, then "goddidit" is redundant as an explanation. Maybe God pushes the Moon in circles around the Earth: but I see no reason not to assume gravity is responsible.

As for Lamarckianism: like "goddidit", it appears redundant. Furthermore, there are two additional problems:

1. How to transmit the "stresses" to the sperm or ovum? A simple stress like hunger might affect the development of the zygote, but how should this be interpreted? Should the next critter avoid hunger by having a lower metabolic rate (less need for food) or a higher one (be more active, run faster, catch more prey)? What sort of chemical messenger could pass on a request for something complicated like "better camouflage"? Is there a hormone for developing khaki disruptive-pattern camouflage, another for a nut-crunching beak, and so on? Biochemists haven't found anything this complex: just hormone triggers in some species which switch between existing "make male" and "make female" paths.

2. Whenever we try it (e.g. the chopping of rat tails), it just doesn't happen. Thus far, when something Lamarckian appears to be happening, it turns out to be a Darwinian effect. For instance, there was speculation that bacteria could raise their mutation rate when this would help them deal with a new stress or exploit a new food. It turned out that this was due to a "mutagenic mutation". Some mutations damage the cell's error-correcting systems and make more mutations likely: normally a harmful trait, so it tends to fizzle out. However, if there is a "need" for rapid changes, those which are likely to develop them are the more rapidly-mutating ones, leading to preferential selection of rapid mutation and a period of accelerated evolution until the bug has adapted to the new niche. In this example (Cairns IIRC), the mutagenic mutation was actually found.

Motorcycle Mama

On point number 1, Lamarck, to the best of my knowledge, never explained how attributes were transmitted to sex cells; I'm not even sure he knew about them.

Point number 2, to me, argues that the driving force of evolution is mutation and the role of natural selection is to act, not as a directing agent, but one to winnow out certain types. If the driving force is mutation then the cause of evolution would seem to be whatever it is that causes mutations, X-rays, UV, thermodynamic instability, etc.
MM

Xixax

Again, you're focusing on a narrow band of an explanation. Some times, natural selection weeds out destructive mutations, other times it serves to encourage increased complexity ( like the encouragement of advanced sensory organs ). Other times an environment changes where what was once considered more destructive than advantageous is now considered advantageous ( like the example given above ).

Would evolution happen with those things you mentioned causing mutations? No. Would evolution happen in the way we see it happening without natural selection? No. Are their other factors that weigh in on evolution besides RM&NS? Yes. Does Darwinian evolution allow for this? Yes.

The power of natural selection is that it provides a backing of teleology behind the direction of evolution. It's no longer a blind march towards complexity or simplicity. It's a predictable and purposeful process. It serves as a guide to the rest of evolution, and some times even provides momentum.

[ October 28, 2002: Message edited by: Xixax ]</p>

Motorcycle Mama

First, I very much liked your last paragraph. A relationship between natural selection (in my lexicon Darwinian evolution) and teleology is one of its main features.

I'm not sure that I completely follow the remainder of your arguments. As I read them they seem to assume that any change, e.g., an increase of decrease in complexity, the appearance of elaborate structures, is the result of natural selection. I realize this is a common argument but one that, to me, lacks both a mechanism and meaning. The reason it lacks meaning is that in such arguments natural selection becomes such a broad topic that everything is included as an example of it.

It isn't clear to me why mutation alone can't cause evolution. While I myself can't do it it should be quite easy to produce a computer program that introduces some sort of change with the resulting product looking like evolution. I think the graphics produced with one part of chaos theory does just that. This would be evolution without natural selection, granted in a model system.

Granted it is a truism there are factors other than random mutation and natural selection admitted to in Darwinian evolution. But what are they? Darwin in the Origin of Species talks about other factors and when he is explicit about them those other factors are the effect of the environment on organisms and what Darwin is arguing for is a form of Lamarckian inheritance. The difference is the effect of the environment in Darwin's version is on the subsequent generation rather than the one affected. There are other factors invovled in evolution, one that was posted in this exchange was, in my words, directed mutagenesis and that was related to natural selection. But I have a question. Is directed mutagenesis part of Darwin's views, given that he was unaware of mutations? I would say no since Darwin's natural selection was the effect of something external to the organism and directed mutagenesis seems to be a property of the organism itself, i.e., an example of Lamarck's drive towards increased complexity.

My final comment on a post that is becoming too long is about the concept of random mutation. It is a specific use of random, i.e., the specific effect of a mutation cannot be known and mutations are independent of the environment. An assumption of random mutation is necessary for Darwinian evolution to occur but has it ever been demonstrated? I can't think of any case where it has been adequately tested and there are some microbiologists who are arguing in favor of what would appear to be environmentally directed mutations.

What I have seen over the last while is that any event that is considered to be evolutionary is ascribed to Darwin in spite of those events not being part of what Darwin talked about, or even contrary to it. I have even read that the universe is to be explained in terms of natural selection or that Darwin, and not Einstein, was the father of relativity. As much as I may not like that it is what seems to be happening. So a reasonable person might ask why I am so perverse in holding on to anti-Darwinian views. First they allow a vast array of apparently contrary beliefs. One can argue, as some anti-evolutionists do, that following Darwin, natural selection is the cause of evolution (Darwin does say that) and because natural selection is flawed, evolution is flawed. One the other hand one can argue that the view of increasing complexity is consistent with Darwin even though it is possible to demonstrate that natural selection is a complexity reducing phenomenon. Second, Darwin, in my opinion, did two disservices to biology. First he encouraged a reductionist view, if you want to understand evoluttion you have but to discern the effects of natural selection, usually on single characters. Second, because natural selection affects functional features, Darwin, by default, placed function as preeminent over structure. But it is structure that evolves and not function.

When I sat down at the computer this morning I told myself I had other responsibilities and I had to practice restraint on any post I produced. Obviously the argument caught my interest at a level that temporarily set aside those other responsibilities. But now I must act like a mature adult.
MM

seanie

I'm not clear on what's meant by natural selection providing a teleology to evolution. I can see natural selection providing a direction ie. improvement (whatever that constitutes).

But it doesn't provide a goal as such. Whilst natural selection may not be blind to each step (an advantage is seen and rewarded) it is blind beyond that. If all you can see is one step in front I think that still constitutes a (fairly) blind march.

As far as I can see the advantage of natural selection, and what makes it stand out as a mechanism, is it's ability to generate complexity. It requires mutation to act upon but by rewarding small advantages and punishing small disadvantages it can accelerate and accumulate change. Each improvement is jelously preserved and built upon and so on and so forth.

The great distinction of Natural Selection is its riposte to the argument from design that living organisms were so complex that they couldn't have arisen by chance. That observation was fundamentally correct. Living organsims are too complex to have arisen purely by random. Darwin's great claim was to show how random mutation coupled by non-random natural selection could plausibly account for such complexity.

Relying on mutation alone you come back to a problem of improbability. Natural selection may not be the only mechanism in evolution but it seems to be the best (perhaps only?) one that accounts for complexity. And that's because (at every available opportunity) it provides direction. It drives evolution to improvement regrdless of whether that entails complexity or simplicity.

Clutch

MM,

Speaking as a former student of yours -- I learned a good deal of realism about scientific practices from you, and remember your class fondly -- I have to say your opening post is an atrocious example of bad argumentation, and rests almost entirely on hinting where you cannot prove. A quote from a friend of Darwin? A charge of sexism cobbled out of mixed quotation where all the most incriminating material is yours, and not Darwin's?

Yuck.

So far, I see a bad argument for a conclusion irrelevant to the soundness of Darwinian evolutionary theory. And I see a rather baroque and scientifically unfecund description of evolutionary processes in thermodynamical terms, which, even were it a true description, seems quite clearly compatible with Darwinism, classical, neo-, or whatever.

In this thread and others, you have resisted presenting anything like a careful or sustained critique of Darwinism, nor a detailed defense of the "semiotic" view you seem to prefer (the utter failure of semiotic explanation in every field to which it has yet been applied apparently spurring the decision to invoke it in biology...). Rather, you have resorted to vague insistences that anti-creationists here are egregiously uninformed in ways, and with relevant consequences, that you have found impossible to articulate.

It strikes me that your tendency towards iconoclasm and healthy curmudgeonliness has become a rationally impoverished nay-saying, and an uncritical acceptance of an approach that affords a platform from which to object to all things Darwinian.

However, I still remember and laugh at the wonderful definition of a botanical niche as "the closest place a plant occurs to the spot where the botanist has to park the Jeep and start walking." My two cents is that you're in need of sorting yourself out on this anti-Darwin obsession. I wish you good luck on it.

Xixax

That's too simplistic a statement to encompass what I meant. I am new to the subject, relatively speaking ( having only studied it for a few years ), but I will make another attempt at the argument again.

To simplify it, I'll use the word complexity in place of the rest ( increased functionality etc. ).

Complexity is not the result of natural selection alone. Sometimes, natural selection may have very little or nothing to do with the complexity.

In order for natural selection to have anything to select for, there must have been at first a mutation. That mutation must not have only happened, but it also must have had an expressed change in the structure of the organism. Even on change of structure, that change of structure must have an expressed change, enhancement or detriment, to the organism's function as well.

When someone talks of natural selection being a cause of complexity, they are not in any way trying to diminish the importance of all those other factors. The mathematics and physics behind mutations is undeniably important and crucial for understanding evolution. However, it cannot explain some instances of complexity on it's own.

The mathematical shapes and structures that appear complex that come from fractal algorithisms are not analogous to most instances of complexity in organisms. Those shapes and structures have no purpose. If you ask, what does that shape do, the answer will not change even if you modify some small segment of the algorithm that drastically changes it's structure and appearance.

However, an eye, an ear, a wing, a sharp tooth, all of those serve a purpose for survival in the organism. In those cases, if increased complexity also means an increase in the survivability of those organisms, there will be an unavoidable tendency for more complexity until:

1) The disadvantages of building such complexity outweigh the advantage of the complexity
2) Mutations in those features stop providing marked improvement in survivability
3) The environment changes in a way that the complexity already attained is no longer necessary
etc.

A poor argument for a good theory doesn't invalidate the theory.

It can produce some evolution, but it could not produce an eye like ours. What would make mutation alone move towards our particular eye structure? How can mutation alone account for symbiotic relationships between two organisms?

Besides that, I can't see how evolution can occur without natural selection happening. Two organisms in the same niche, one more able to survive than another, that same one will eventually displace the less fit organism. It's unavoidable because of limited resources. If there was limitless resources for the two organisms to live off of they may very well continue forever without either displacing one another, but that isn't the case.

I'm in the process of finishing an application now that does the following, inspired by this conversation alone:

It uses a long string of numbers as it's gene. Those numbers are interpreted to get a shorter string of expressed letters. Those letters are then used to determine functionality in various segments:

Longevity, # of offspring, how often it reproduces, how often it must eat, what it eats, what type of 'product' it is considered so that predators can emerge to feed off of it, how lethal it is, its mobility, its preferred 'geosphere ( air/land/water ), how aware it is,

Then I have a world cycle that takes each time segment ( we'll call it days to make it easy ), and determines if it died from starvation, caught prey or food, reproduced, died from old age etc.

I'm currently playing with it in an early stage, and already there is a tremendous 'sweet spot' where too many mutations are bad, and too few cause a group to be displaced. I'm playing now with making drastic changes to the environment ( suddenly limiting the amount of available resources... causing little extinctions etc. ).

I'll let you know how it goes when it's finished, but I think it will be illustrative of the way that natural selection works to cause increased complexity in some cases. ( Yes, I took the time to make a completely 'clueless' replicator function, it knows nothing of the purpose of the genetic information, and actually gets its cues on when to start and stop on little codes etc.... I'm quite proud. )


Genetic drift is one. Species being separated from each other geographically is another. Sexual selection.... I'm sure others here could name more.

I think you're asking if it has been shown that mutations are in fact random instead of directed. I'll do my best to find some articles tomorrow morning for you that point to that being the case, but I can easily think of ways they have determined this. The amount of nonsense in our genes is a very good indicator that mutations are not directed. Directed mutations would seem to rule out a large amount of useless genetic information. It would also limit the amount of mutations you would expect to see that have the exact opposite effect as is necessary for survival ( an organism developing toxic reactions to things readily found in it's environment )

Some links? I'm not being doubtful, it's just that in my travels across the web I have yet to come across any that aren't 'quacks', making obvious errors in their conclusions ( I consider obvious any error a layperson like myself can see within minutes ).

Well, no more so than some physics are anti Newtonian, even though Netwon is generally felt to have discovered gravity.

Not at all! We describe individual characters because it is easier to do so. To understand the way natural selection progresses and influences evolution, you must take it as a whole of an organism combined with the environment it's in.

Darwin didn't encourage reductionism, he also didn't encourage social darwinism either. People took the theory of evolution and applied it everywhere, wrongly in many cases. It doesn't mean its application to biology is wrong, just that people are prone to latch onto great ideas and abuse them.

Structure doesn't evolve, the recipe for structure evolves, which influences structure, which influences function.

My largest problem with discussion if they become extremely deep is that I only have .net access from work, so everything I do here is in a temporary break I have from my duties. Since I can't control the length of those, I can't really post the type of details others are so generously able to provide.

When I finish this little evolution application, I'll happily forward results or a copy if you want.

[ October 29, 2002: Message edited by: Xixax ]</p>