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Author Topic:   Criticizing neo-Darwinism
nwr
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Posts: 5727
From: Geneva, Illinois
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Message 1 of 309 (296949)
03-20-2006 8:58 PM


In Message 92 I expressed my opinion that the traditional neo-Darwinist account of evolution is one that many people, not just creationists, find implausible. Parasomnium has answered this in Message 97 (same thread). This current topic is intended to provide a place where I can continue this debate with Parasomnium and others, since it would take the earlier thread off topic if continued there.

Parasomnium nicely summarized the neo-Darwinian position I was criticizing, with

Not wishing to blow my own horn, I must say I find nothing more plausible than the fact that, if hereditary information randomly changes, which is a fact, and if the environment can only sustain the better adapted, which is also a fact, then the adaptive changes are preserved at the expense of the less well adapted. A long cumulation of these changes naturally leads to extremely well adapted, very complex structures.

That's the account I find problematic. It is roughly the same as the "Selfish Gene" account popularized by Dawkins. While I find that account problematic, I do not question that evolution occurred. I just want a better formulation than that of traditional neo-Darwinism.

This topic is for discussing the problems with that particular neo-Darwinian account. It is not for arguing whether evolution happened or is happening.


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AdminJar
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Message 2 of 309 (296951)
03-20-2006 9:03 PM


Thread moved here from the Proposed New Topics forum.

  
nwr
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Posts: 5727
From: Geneva, Illinois
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Member Rating: 4.4


Message 3 of 309 (296964)
03-20-2006 10:08 PM


This is a response to Message 97 by Parasomnium.

Parasomnium writes:

The mathematics of evolution, especially the mathematics of the probabilities involved, are often misunderstood.


I agree. However, mathematicians tend to understand the mathematics better than non-mathematicians. Fred Hoyle was no slouch at mathematics, and he found fault with the neo-Darwinist account.

Not wishing to blow my own horn, I must say I find nothing more plausible than the fact that, if hereditary information randomly changes, which is a fact, ...

Agreed so far.

..., and if the environment can only sustain the better adapted, which is also a fact, then the adaptive changes are preserved at the expense of the less well adapted.

That's where the argument begins to run into problems. The expression "better adapted" is itself a little vague.

There is a saying "The early bird gets the worm." But it wasn't a matter of being less well adapted that caused the worm to be eaten. It was just bad luck that the bird happened to be around at that time. There are many contingencies of life that affect whether an individual survives to reproduce. Differences in how well adapted are only part of the story. Sure, there might be a statistical filtering effect. But for small differences in how well adapted, this filtering is a weak effect in a sea of contingencies. Any filtering would be very slow, and in my opinion it would be too slow to account for biological diversity.

It could be that a slightly deleterious gene occurs on the same chromosome as a slighly beneficial gene. Since they are on the same chromosome, they tend to be inherited together. The disadvantages of the one are offset by the benefits of the other, so there is no net filtering effect. Agreed, the two genes can be separated during a crossover. But if they are close together on the same chromosome, then the probability that a crossover will divide them is relatively small. To consider the filtering in this case, you have to look not at the time between generations, but at the time between crossover events that divide between the two genes. The rate of filtering would be extremely slow.

A long cumulation of these changes naturally leads to extremely well adapted, very complex structures.

That's where it becomes downright implausible. The neo-Darwinistic account is one of gradual change. The arguments about irreducible complexity arise because gradual change does not plausibly lead to very complex structures. The biology shows how complex structures can arise, but the gradualism of the neo-Darwinist model seems to argue against it.

I'll toss in another problem. According to neo-Darwinism, evolution advances by adaptation. However, it seems to me that a species cannot exist unless it is already adapted. And becoming over-adapted would only result in exponential growth of a species until it destroyed its own habitat. The only way I can see a species being mal-adapted, is when some environmental change destroys the environment to which a species was previously adapted. Granted, such changes can and do occur, some caused by other evolutionary changes in the biosphere (what Dawkins refers to as an arms race). But I am skeptical that such environmental change can account for all of the adaptation that would be needed to explain the degree of biological diversity and complexity that we find.

Being science-minded, they will certainly not resist your theory if it stands up to rigorous scientific tests and explains things better than the theory of evolution does.

My theory doesn't change the biology at all, so it should stand up to the biological testing. And it would still be a theory of evolution, just not the neo-Darwinist version. But I think you underestimate the resistance to change.

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crashfrog
Member (Idle past 404 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 4 of 309 (296965)
03-20-2006 10:13 PM
Reply to: Message 1 by nwr
03-20-2006 8:58 PM


I'm pretty sure that evolution hasn't technically been "Darwinist" for almost 20 years, now. What's the merit in criticizing "Darwinism"?

The modern theory of evolution encapsulates sexual selection, genetic drift, punctuated equilibrium, and a host of other things that don't fall under the heading of "Darwinism".

I just want a better formulation than that of traditional neo-Darwinism.

Perhaps it would help if you were to elucidate the ways that you find Para's account, which is marvelously simple and obviously correct, to be uncompelling to you.


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NosyNed
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Posts: 8963
From: Canada
Joined: 04-04-2003


Message 5 of 309 (296968)
03-20-2006 10:36 PM
Reply to: Message 3 by nwr
03-20-2006 10:08 PM


Gradualism
The neo-Darwinistic account is one of gradual change.

I was surprised to learn that Darwin, in his original publication of the Origin was not a total gradualist. He even recognized that the speed of evolution doesn't have to be constant. I'm not sure that there as ever been utter gradualism.

PE (punc eck) is simply a statement that the changes in speed may be greater than recognized explicitly before and account for some of the patterns of the fossil record. It is totally within neo-darwinism. Even the extremes suggested there are still "gradual" by everyday standards.

The arguments about irreducible complexity arise because gradual change does not plausibly lead to very complex structures. The biology shows how complex structures can arise, but the gradualism of the neo-Darwinist model seems to argue against it.

You'd have to explain why you think this is so. The problems introduced by IC have NOTHING to do with gradualism as far as pace goes. They do have to do with "step size". However, they do not deal with pathways through evolutionary space.

Biology suggests that large step sizes are unlikely to be successful. To that degree "gradualism" is presented with a problem by IC. However, gradual movement through more complex pathways than one step at a time to a final result works just fine. This is exemplified by the scaffolding approach for one. Coopting for another.

However, it seems to me that a species cannot exist unless it is already adapted. And becoming over-adapted would only result in exponential growth of a species until it destroyed its own habitat. The only way I can see a species being mal-adapted, is when some environmental change destroys the environment to which a species was previously adapted. Granted, such changes can and do occur, some caused by other evolutionary changes in the biosphere (what Dawkins refers to as an arms race). But I am skeptical that such environmental change can account for all of the adaptation that would be needed to explain the degree of biological diversity and complexity that we find.

The question is: Why are you skeptical?

Species do destroy their habitat and go extinct. However, over adaptation (what ever the heck that means) is difficult I think. You have the solution to this just a little further down. The evolutionary arms race is a "red queen's race". That is you have to run faster and faster just to stay in the same place.

You are right that everything alive now is adapted rather well to where it is. Until something changes! And, of course, something is almost always changing. Perhaps slowly but on rare occasions more rapidly.

It could be that a slightly deleterious gene occurs on the same chromosome as a slighly beneficial gene. Since they are on the same chromosome, they tend to be inherited together. The disadvantages of the one are offset by the benefits of the other, so there is no net filtering effect. Agreed, the two genes can be separated during a crossover. But if they are close together on the same chromosome, then the probability that a crossover will divide them is relatively small. To consider the filtering in this case, you have to look not at the time between generations, but at the time between crossover events that divide between the two genes. The rate of filtering would be extremely slow.

I don't know enough genetics to be sure but I think you are wrong in what you are stating here.

Sure, there might be a statistical filtering effect. But for small differences in how well adapted, this filtering is a weak effect in a sea of contingencies. Any filtering would be very slow, and in my opinion it would be too slow to account for biological diversity.

Again I am not an expert but I believe that the math of population genetics says that your opinion is wrong.


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RAZD
Member (Idle past 342 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 6 of 309 (296969)
03-20-2006 10:48 PM
Reply to: Message 1 by nwr
03-20-2006 8:58 PM


muddled thoughts.
It is roughly the same as the "Selfish Gene" account popularized by Dawkins.

No amount of genetic "selfishness" allowed large dinosaurs to survive the KT extinction event.

The problem I have is that genes don't get selected on their own, that they are necessarily {groups\sets\associations\clubs}.

The evolutionary result can be derived from a "profligate" {set of genes} that necessarily have numerous small genetic "errors in translation" in the process of making a {carrier\progeny} such that there are a number of near copies (of the whole {group\set\association\club}) made ... of which the best copies survive -- when tested.

But not every generation is tested by {competition\environmental} factors, and not every individual in a generation is tested by {genetic\developmental} factors (although very poor adaptations would be readily eliminated). Environmental factors can reverse over the course of a species lifetime.

This means that there is often quite a bit of mixing up of {carrier\progeny} bits and pieces by generations of reproduction before any selection testing takes place.

This can result in stasis because you are looking at the difference between a bell curve with 100 data points and a bell curve with 10,000 data points - the average is the same, and the only difference is in the extreme ends where the numbers are necessarily low in proportion to the population.

To me this also means there can be some 'backin-an-fillin' around a general "trendency" rather than a progression, whenever there are no extreme tests, but there are oscillating factors (like {environment\climate} or population {explosion\contraction}).

And this can result in "spandrels" that have no apparent purpose or function, variations on a theme (which perhaps can lead to 'accidental' speciation when potential mates do not recognize each other as mate-able -- a la ring species {termination\overlaps}). Curly hair versus straight. Blue eyes.

But they are not necessary, nor is the development of more complex structures when the existing ones are adequate.

In the absence of extreme events life kind of just muddles along, all the available niches are pretty well filled with species that are adequately adapted to them, and the relationship of species to environment, to others (competition, predation), whatever, is pretty constant.

When extreme events occur they may overwhelm the ability of adaptation to allow survival, so it may just be a case of life that existed outside the test area picks up the slack rather than any survivors.

Certainly this appears to have been the case following the major extinction events, where other species moved in to fill the voids in the available niches.

Not sure this helps ...


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Parasomnium
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Posts: 2194
Joined: 07-15-2003


Message 7 of 309 (296991)
03-21-2006 5:45 AM
Reply to: Message 3 by nwr
03-20-2006 10:08 PM


Defending neo-Darwinism
nwr writes:

mathematicians tend to understand the mathematics better than non-mathematicians. Fred Hoyle was no slouch at mathematics, and he found fault with the neo-Darwinist account.

Well, apart from stating the obvious about mathematicians, your mentioning Fred Hoyle doesn't do your argument much good either. Hoyle was not a mathematician, he was an astronomer, and a controversial one at that. Although he coined the term "Big Bang" himself, he fervently opposed the idea, even in the face of ever accumulating evidence for it. His equally fervent opposition against chemical evolution, culminating in his comparison of the random emergence of even the simplest cell to the likelihood that "a tornado sweeping through a junk-yard might assemble a Boeing 747 from the materials therein", is a prime example of the misunderstanding of the probabilities involved, which I mentioned earlier.

..., and if the environment can only sustain the better adapted, which is also a fact, then the adaptive changes are preserved at the expense of the less well adapted.

That's where the argument begins to run into problems. The expression "better adapted" is itself a little vague.

[...] There are many contingencies of life that affect whether an individual survives to reproduce. Differences in how well adapted are only part of the story. Sure, there might be a statistical filtering effect. But for small differences in how well adapted, this filtering is a weak effect in a sea of contingencies. Any filtering would be very slow, and in my opinion it would be too slow to account for biological diversity.

Of course you are right in saying that chance plays a part in how evolutionary history unfolds: even what might be considered the best adaptations to the current environment may not protect a creature against very sudden, haphazard changes like asteroid impacts and such. However, events like that kill indiscriminately, leaving the statistical filtering effect you mentioned firmly in place. Any net filtering effect will inevitably lead to diversification, it just remains to be seen how fast it proceeds. Since you question the adequacy of the speed with which it takes place, it's up to you to show that it's too slow if you do not wish to be accused of personal incredulity.

I'd like to point out that the sheer numbers involved, in terms of the individuals and generations that have passed, and the vast gulf of time this has taken, are mind-boggling. I think that personal incredulity might well be a symptom of a boggled mind.

A long cumulation of these changes naturally leads to extremely well adapted, very complex structures.

That's where it becomes downright implausible. The neo-Darwinistic account is one of gradual change. The arguments about irreducible complexity arise because gradual change does not plausibly lead to very complex structures. The biology shows how complex structures can arise, but the gradualism of the neo-Darwinist model seems to argue against it.

You will have to explain this in more detail to convince me. How does gradual change not plausibly lead to very complex structures, and how does the gradualism of the neo-Darwinist model seem to argue against it?

According to neo-Darwinism, evolution advances by adaptation. However, it seems to me that a species cannot exist unless it is already adapted.

You seem to assume that being adapted is an all-or-nothing quality. Although I am sure you don't mean it that way, you might want to reassure me.

The only way I can see a species being mal-adapted, is when some environmental change destroys the environment to which a species was previously adapted. Granted, such changes can and do occur, some caused by other evolutionary changes in the biosphere (what Dawkins refers to as an arms race). But I am skeptical that such environmental change can account for all of the adaptation that would be needed to explain the degree of biological diversity and complexity that we find.

Isn't that just more personal incredulity you are displaying here? Could you somehow quantify your skepsis?

Being science-minded, they will certainly not resist your theory if it stands up to rigorous scientific tests and explains things better than the theory of evolution does.

My theory doesn't change the biology at all, so it should stand up to the biological testing. And it would still be a theory of evolution, just not the neo-Darwinist version. But I think you underestimate the resistance to change.

If your theory is a theory of evolution, it should not just stand "biological testing", whatever that means, but it should stand evolutionary testing, i.e. it should make evolutionary predictions that could be verified.

This message has been edited by Parasomnium, 21-Mar-2006 02:35 PM


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Chiroptera
Inactive Member


Message 8 of 309 (297022)
03-21-2006 9:09 AM
Reply to: Message 3 by nwr
03-20-2006 10:08 PM


quote:
However, mathematicians tend to understand the mathematics better than non-mathematicians. Fred Hoyle was no slouch at mathematics, and he found fault with the neo-Darwinist account.

Replace "mathematician" with biochemist and "Fred Hoyle" with "Michael Behe" and you have Behe's famous taunt to evolutionary biologists who, he claims, don't really understand biochemistry.


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EZscience
Member (Idle past 4091 days)
Posts: 961
From: A wheatfield in Kansas
Joined: 04-14-2005


Message 9 of 309 (297038)
03-21-2006 10:13 AM


Units of selection and units of evolution
I think this discussion might benefit from everyone specifying the units of evolution they are referring to when they talk about evolutionary process. RazD has made reference to this, but many other references to evolutionary processes do not specify the units under discussion or distinguish between genes, individuals, or species and this is important.

The gene is a unit of inheritance, not a unit of selection. The lowest level at which selection can act is on the individual. This is also the level at which selective forces are strongest. Selection in some forms can sometimes act at higher levels (groups), but discussions about species evolution often erroneously imply that selection acts on species - it doesn't. Species, as gene pools, are units of evolution, but they are not units of selection. Similarly, adaptations are a property of populations or species, not individuals. A species' fate (persistence, divergence into many other species, or extinction) is some function of its genetic potential, inherent biological constraints determined by its phylogeny, and chance events, all played out in the context of a changing environment. Species can evolve/adapt quickly under some circumstances, slowly under others, or remain virtually unchanged for millenia. Thus biological complexity is one possible outcome of species evolution, but it is not an inevitable result.

This message has been edited by EZscience, 03-21-2006 09:14 AM


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nwr
Member
Posts: 5727
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.4


Message 10 of 309 (297078)
03-21-2006 1:22 PM
Reply to: Message 4 by crashfrog
03-20-2006 10:13 PM


Perhaps it would help if you were to elucidate the ways that you find Para's account, which is marvelously simple and obviously correct, to be uncompelling to you.

I thought I did that. Apparently Para thought so to, and has responded. I will continue that debate.

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nwr
Member
Posts: 5727
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.4


Message 11 of 309 (297083)
03-21-2006 2:00 PM
Reply to: Message 5 by NosyNed
03-20-2006 10:36 PM


Re: Gradualism
I'm not sure that there as ever been utter gradualism.

Probably correct. However, this debate isn't about evolution. It is about the adequacy of the neo-Darwinian account of evolution.

The problems introduced by IC have NOTHING to do with gradualism as far as pace goes. They do have to do with "step size". However, they do not deal with pathways through evolutionary space.

They have to do with whether a sequence of steps is required, such that intermediate steps should be impossible or very unlikely due to negative selection against them. To me, this does seem to be a problem in the neo-Darwinian account, although I don't see a problem in the biology. If I'm right, that would argue that there is a problem with neo-Darwinism.

The question is: Why are you skeptical?

Remember that my comment was in the context of an assumed neo-Darwinian model.

As is often the case with mathematical modelling, the model doesn't fully match reality. IMO the mismatch is serious, and the model is not adequate for the job.


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nwr
Member
Posts: 5727
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.4


Message 12 of 309 (297085)
03-21-2006 2:06 PM
Reply to: Message 6 by RAZD
03-20-2006 10:48 PM


Re: muddled thoughts.
No amount of genetic "selfishness" allowed large dinosaurs to survive the KT extinction event.

In my opinion, neodarwinism explain extinction rather well. But it doesn't do so well at accounting for novelty. You can account for the novelty by appealing to the biology. But if neodarwinism were a good model, then you should not have to keep appealing to the biology to help the model over its weak points.

The problem I have is that genes don't get selected on their own, that they are necessarily {groups\sets\associations\clubs}.

That's one of the over-simplifications made by the model.

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nwr
Member
Posts: 5727
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.4


Message 13 of 309 (297090)
03-21-2006 2:54 PM
Reply to: Message 7 by Parasomnium
03-21-2006 5:45 AM


Re: Defending neo-Darwinism
Well, apart from stating the obvious about mathematicians, your mentioning Fred Hoyle doesn't do your argument much good either.

I'm well aware that he is not very popular among evolutionists. Still, he did go to some effort to work out the implications of neo-Darwinist assumptions.

His equally fervent opposition against chemical evolution, culminating in his comparison of the random emergence of even the simplest cell to the likelihood that "a tornado sweeping through a junk-yard might assemble a Boeing 747 from the materials therein", is a prime example of the misunderstanding of the probabilities involved, which I mentioned earlier.

Hoyle did have a way with rhetoric. As far as I know, that comment was based on the neo-Darwinian model, rather than on what is observed biologically. To show he misunderstood the probabilities, you would have to show that his mathematical analysis was wrong. An appeal to empirically observed probabilities would tend to support Hoyle's conclusion that neo-Darwinism provides a poor account.

Any net filtering effect will inevitably lead to diversification, it just remains to be seen how fast it proceeds.

This is what is not obvious to me (assuming the neo-Darwinian model).

The model is usually described as one of optimizing the degree of adaptation. Supposedly the early earth was inhabited only by algae. So why are we here? Why does the biosphere not consist only of optimally adapted algae?

Since you question the adequacy of the speed with which it takes place, it's up to you to show that it's too slow if you do not wish to be accused of personal incredulity.

Perhaps my wording was a bit confusing. I don't see that speeding up the filtering would help. The model still does not adequately explain novelty.

You will have to explain this in more detail to convince me. How does gradual change not plausibly lead to very complex structures, and how does the gradualism of the neo-Darwinist model seem to argue against it?

The problem is that the change is described as optimizing what is already there, rather than as introducing novelty.

You seem to assume that being adapted is an all-or-nothing quality. Although I am sure you don't mean it that way, you might want to reassure me.

Sloppy wording. In my preferred alternative theory, I think of degree of adaptation as a numeric value. Roughly, it is the ratio of the expected population size of the next generation to the population size of the current generation (where "expected" is in the probabalistic sense).

In practical terms, a degree of adaptation significantly less than 1 would indicate a species on the path to extinction. A degree of adaptivity greater than 1 would lead to exponential growth, so could not be long sustained. Thus a degree of adaptation that hovers around 1 is what would be needed for a species to be considered well adapted.

----------

If your theory is a theory of evolution, it should not just stand "biological testing", whatever that means, but it should stand evolutionary testing, i.e. it should make evolutionary predictions that could be verified.

It predicts punctuated equilibria as a significant mode of speciation. It predicts that novelty will arise.

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nwr
Member
Posts: 5727
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.4


Message 14 of 309 (297093)
03-21-2006 2:59 PM
Reply to: Message 9 by EZscience
03-21-2006 10:13 AM


Re: Units of selection and units of evolution
I think this discussion might benefit from everyone specifying the units of evolution they are referring to when they talk about evolutionary process.

From my perspective, selection is primarily of individuals. It is a species (or a population) that evolves.

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crashfrog
Member (Idle past 404 days)
Posts: 19762
From: Silver Spring, MD
Joined: 03-20-2003


Message 15 of 309 (297095)
03-21-2006 3:47 PM
Reply to: Message 12 by nwr
03-21-2006 2:06 PM


Re: muddled thoughts.
But if neodarwinism were a good model, then you should not have to keep appealing to the biology to help the model over its weak points.

This is nonsense to me. What would be the basis of an evolutionary theory besides the biology of the organisms that are evolving? Evolution is a theory of biology. Why do you believe it is wrong to appeal to biology to explain evolution?


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