Reasons Behind the Theory of Evolution by Natural Selection

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Re: Reasons Behind the Theory of Evolution by Natural Select

Post Number:#46  Postby ape » January 2nd, 2010, 10:51 am

Hi Alun,


Your conclusions are fair and excellent!:)


This has been a good discussion due to our attitudes, and I hope that you and I have set an example for others of any persuasions to also exemplify!:)


You DO have everything, especially old, and new, to teach the world!:)
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Re: Reasons Behind the Theory of Evolution by Natural Select



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Post Number:#47  Postby Belinda » January 3rd, 2010, 7:54 am

From Alun's OP
C1-3) If a mutation does not help an organism reproduce, there will not be any pressure for that change in genetic information to promulgate.
* This is microevolution by natural selection. We see it all the time in antibiotic-resistant bacteria.

Aren't some mutations linked with other,more reproduction -significant mutations? I mean, some of the traits we see in various creatures may not help the individual to live to be someone's ancestor because that trait is either redundant or is positively bad for the possible ancestor but because it is linked to and trumped by the 'good' trait, it survives.
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Post Number:#48  Postby Meleagar » March 7th, 2010, 9:35 am

The problem is that your final conclusion:

Alun wrote:C3-4) Evolution in the past can be explained as a consequence of species divergence due to reproductive pressure.


cannot be logically arrived at by your previous argument.

If we assume that a process which can acquire X amount of variation (microevolutionary variances), it does not follow that such a process can achieve any amount of variation or change, because the landscape between two variances might include obstacles that are categorically different than that which is known to be travresable by the accepted process.

An analogy would be that walking can get one from your house in Kansas City to the store down the street, but it cannot get you to Japan, even though both are known physical locations, and even though people in Japan can walk from their home to the store down the street.

Just because a species can take a walk over time to a different beak size, or variant colorations, or larger or smaller scales or differently-shaped claws, doesn't mean that any location, or any variance whatsoever, is available by the same walking process.
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Re: Reasons Behind the Theory of Evolution by Natural Select

Post Number:#49  Postby Alun » June 20th, 2010, 11:26 pm

I may not stick around for long, and obviously I'm late to my own topic here, but I figured this thread could use some attention.

Hi ape
ape wrote:Your conclusions are fair and excellent!:)

My reply is late in coming, but I must say I'm pleasantly surprised that you're so satisfied. Thanks for the discussion!

_______________________________________________

Hi Belinda
Belinda wrote:Aren't some mutations linked with other,more reproduction -significant mutations? I mean, some of the traits we see in various creatures may not help the individual to live to be someone's ancestor because that trait is either redundant or is positively bad for the possible ancestor but because it is linked to and trumped by the 'good' trait, it survives.

Yes, there are a lot of ways this can happen at the level of phenotype and genotype. For example, a single mutation may affect two genes, having both a good an bad result. Alternately, a single mutation may have both a good and bad result. The latter case is, from what I know, far more likely, since genes don't target just one process in one type of cell, but have systemic ramifications for the entire organism.

I intended to refer to the overall effect of a single process of mutation--rather than a single changed gene, which seems to be how you read it.

________________________________________

Hi Meleagar

Meleagar wrote:If we assume that a process which can acquire X amount of variation (microevolutionary variances), it does not follow that such a process can achieve any amount of variation or change, because the landscape between two variances might include obstacles that are categorically different than that which is known to be travresable by the accepted process.

That's true, but I did not say, "Any and all sorts of evolution are in fact explained..." The point of this thread was to show that the theory of evolution by natural selection is not conceptually incoherent--it is in fact conceptually convincing. (Note that this is a philosophy of science forum, not a science forum.) I suspect that neither of us is qualified to vet the statistical data inferred from experiments analyzing genetic variation and natural selection, nor the data from historical genetic variation, but experts in the field routinely do so and bolster the concepts I'm advancing here with empirical evidence.

_______________________________________

I would edit the OP to clarify the portions being contended, but I see that this feature has been removed in my absence. As such all I can do is apologize for what is unclear; I wish I could make changes to reflect some of the positive criticism.
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Post Number:#50  Postby Belinda » June 21st, 2010, 6:11 am

Alun replied to Belinda
I intended to refer to the overall effect of a single process of mutation--rather than a single changed gene, which seems to be how you read it.


My mistake. I note your reply to Meleagar, about this being a philosophy forum, not a science form.I will try to remember your phrase 'conceptually convincing'.

However, in our capacity as philosophers, is the motivations of the particular philosopher relevant or not?

What I mean is that , for instance, we may say of Plato that he was an aristocrat and surmise that this fact underlies his philosopher kings political theory. So in the case of alternatives to natural evolutionary processes we may surmise that their protagonists have an ideological agenda.

In support of the scientific approaches to explanations of speciation we can safely say that scientists actively and objectively research possible instances where natural processes may be falsified.None have yet been found but scientists continue to retain open minds because open minds are necessary for scientific endeavours.
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Post Number:#51  Postby Alun » June 21st, 2010, 8:21 am

Belinda,
Belinda wrote:My mistake. I note your reply to Meleagar, about this being a philosophy forum, not a science form.I will try to remember your phrase 'conceptually convincing'.

Actually if I were able I would go back and modify the unclear wording in the OP, and perhaps embolden the "can" in the conclusion.
Belinda wrote:However, in our capacity as philosophers, is the motivations of the particular philosopher relevant or not?

That depends on exactly what the issue is. In this case, the coherency of the argument should be an objective fact. However, it is only an argument about the possibility of evolution by natural selection: Whether it is more or less intuitively convincing that natural selection really did and does cause evolution is certainly going to depend on predispositions about the evidence and alternatives.

As such, I do not expect thinkers like Nick_A, Juice or Meleagar to all of a sudden take kindly to the theory, but I do expect that they will see that the theory is not dead on arrival (if my argument does in fact follow). The other thing I hope the argument shows is how evidence for the theory of evolution by natural selection might be collected, and some examples of that evidence--generally, just that the theory is reasonable.
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Post Number:#52  Postby Meleagar » June 21st, 2010, 6:07 pm

It's only conceptually fulfilling, IMO, to those who don't recognize the fallacy of composition you've committed, which I've already explained.

Just because a process is known to produce some biological variation doesn't mean that the same process can produce any and every biological feature we observe, even if given any amount of time and any amount of resources.
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Post Number:#53  Postby Alun » June 21st, 2010, 7:34 pm

Hi Meleagar,

What I am saying is that to make the argument you want, significant empirical/scientific evidence is required, much of which is surely beyond both of our expertise and not philosophy. This is distinct from the problem of showing the conceptual possibility of evolution by natural selection. Surely you understand that an argument can show "evolution by natural selection is not an inherently contradictory or implausible explanation of species variation," without showing "evolution by natural selection is the exclusive explanation of any and all species variation."

In general, conceptual arguments against evolution by natural selection have centered on (0) scientific method, (1) the history of life on earth, (2) the nature of mutations, (3) the nature of reproductive/natural selection, and (4) the possibility of trait changes and species divergence. That is why I divided up the argument as I did.

It was not my intent to claim that any and all species divergence or trait changes which have been inferred from the historical record are explained by this argument for natural selection. At best, I have shown the backbone of the theory's explanatory structure, where each individual case requires a lot of scientific work to be a fleshed out explanation.
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Post Number:#54  Postby Meleagar » June 21st, 2010, 9:38 pm

Alun wrote:
What I am saying ...


I know what you were saying. IMO, you have not made such a case; you have not shown that natural selection is a conceptually coherent vehicle to get from point A to point Z by demonstrating that it can get you from point A to point B.

The reason it is not coherent is because it fails due to the fallacy of composition. Being able to get from A to B in no way makes a case for getting from A to Z, any more than being able to walk from my house to the store on the corner means I can also walk to Alpha Centauri, given enough time.

Z might be categorically different from B; Alpha Centauri, as a travel destination, is categorically different from the store on the corner; generating functioning winged flight from scratch might be (and, in fact, is) categorically different from "a random mutation to current genome, selected for because it happened to be beneficial in some way".
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Post Number:#55  Postby Alun » June 21st, 2010, 10:55 pm

Meleagar,

Perhaps if you could be more specific, I could understand your criticism. Here is what I hear you saying so far: I gave examples of two species that diverged from a single species do to reproductive selective pressure. That is, evolution from point A to point B.

You're saying that when species divergence occurred from point C to D to E in the past, it is unreasonable to suppose and gather evidence which suggests it might have happened in the same manner as it has been observed between A to B. What I don't understand is what is distinct about the past scenario that makes this unreasonable.
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Post Number:#56  Postby Meleagar » June 21st, 2010, 11:21 pm

Alun wrote:Meleagar,

Perhaps if you could be more specific, I could understand your criticism. Here is what I hear you saying so far: I gave examples of two species that diverged from a single species do to reproductive selective pressure. That is, evolution from point A to point B.

You're saying that when species divergence occurred from point C to D to E in the past, it is unreasonable to suppose and gather evidence which suggests it might have happened in the same manner as it has been observed between A to B. What I don't understand is what is distinct about the past scenario that makes this unreasonable.


You are making the same category error. You are assuming that to acquire Z - functioning winged flight or steroscopic color sight from scratch - that your known A to B process is or can be accumulative towards Z.

Just as no amount of walking can get you significantly closer to the moon, there is no evidence whatsoever that your A to B process can get you significantly closer to Z.

However, since you (1) know someone did get to the moon, and (2) the only locomotive process you are aware of is walking, you think it is a reasonable conclusion that, if you walk long and hard enough, you can get to the moon.

You don't know that eyesight or winged flight **are** accumulations of variations, just as you don't know that a the man on the moon got there by walking. The reasonableness of your methodology is rooted in ignorance about what it takes to get to Z; no conceptual model of "how to get to the moon" can be intelligentlyh considered "reasonable" until one at least knows what it actually takes to get to Z.

"Speciation", which can occur when part of a genome simply degrades sufficiently but in a way that keeps the resulting organism viable, is not the same thing as "manufacturing a novel, deeply complex, functional, interdependent, heirarchial system and its blueprint and a system for activating and manufacturing it from scratch, along with a system for ensuring the blueprint is properly read and transcripted from code".

Equivocating the two is as nonsensical as comparing walking in a haphazard direction and getting "somewhere" with building a functional rocketship and flying it to the moon.
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Post Number:#57  Postby Alun » June 21st, 2010, 11:49 pm

Meleagar, there is not a conceptual difference between evolving one trait by natural selection and evolving the trait of flight or stereoscopic vision by natural selection; empirical investigation is needed to show whether or not the iterative process can make the same leap in both cases.
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Post Number:#58  Postby Scott » June 22nd, 2010, 5:54 pm

I also think the walking to the moon example is a false analogy. Walking to the moon is categorically different to walking across town in a way that walking across the country is not categorically different than walking across the town. In contrast, developing the trait of stereoscopic vision or any one of traits that in combination enable one to fly is not categorically different than developing other traits.

I could see how it would be categorically different to suggest a mouse suddenly gave birth to a bat capable of flight or that a bird gave birth to a fish capable of breathing under water. But of course the numerous drastic differences between those species are extremely greater than the differences that would evolve in a single generation or in a single instance of speciation. But when species G evolves from F which evolved from E which evolved from D which evolved from C which evolved from B which evolved from A, the difference between A and G may be much greater than the difference between A and B or between B and C, etc. This is part of why the moon analogy fails--because the question isn't so much whether the difference between G and A is categorically different than the difference between B and A but rather the question is whether the difference between G and F is categorically different than B and A. If walking across the country can be done by walking across town after town, then even though the difference between 1000 miles and 10 miles is great the difference between any one 10-consecutive-mile set in the 1000 miles and any other 10-consecutive-mile set is not so great; thus it is reasonable to say that both can be done by walking. The theory of evolution does not call for a leap as great as going from point A to F directly, but rather through a gradual step-by-step process, and unlike the difference between going to the moon and going across town, none of those small, gradual steps is that categorically different than the rest. For example, in reference to flying, even among the species that are currently alive right now--not counting the billions who have gone extinct--we can see a vast spectrum from those that can not fly including completely flightless birds and those that can fly best of all with many shades of grey in the middle marked by species who can glide a little to ones who fly for brief, awkward sets occasionally.

Here's a couple images helping show a few different points on the long evolution of flight:

Image

Image

Image

Although, it might be more interesting to talk about the evolution of long-jumping, wings, and feathers before talking about the more simple flight. Talking only of flight is like talking only of bipedal walking. The final jump to bipedal walking from those species closest to it but who didn't walk on only two feet is, like all jumps when broken down to the final step in a long small-step-by-small-step process, small.
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Post Number:#59  Postby Meleagar » June 22nd, 2010, 6:17 pm

Scott wrote:I also think the walking to the moon example is a false analogy. Walking to the moon is categorically different to walking across town in a way that walking across the country is not categorically different than walking across the town.


Yes, that was my point. Until one knows they are not making a categorical mistake, then claiming that a process that can lead to one goal can accumulatively lead to the other. We don't know that the two goals are in the same category.

In contrast, developing the trait of stereoscopic vision or any one of traits that in combination enable one to fly is not categorically different than developing other traits.


Please support this assertion. You might begin by defining "traits", then showing what traits have been empirically demonstrated to be produced by natural selection, and what is involved in generating a trait like stereoscopic vision.

I could see how it would be categorically different to suggest a mouse suddenly gave birth to a bat capable of flight or that a bird gave birth to a fish capable of breathing under water. But of course the numerous drastic differences between those species are extremely greater than the differences that would evolve in a single generation or in a single instance of speciation. But when species G evolves from F which evolved from E which evolved from D which evolved from C which evolved from B which evolved from A, the difference between A and G may be much greater than the difference between A and B or between B and C, etc. This is part of why the moon analogy fails--because the question isn't so much whether the difference between G and A is categorically different than the difference between B and A but rather the question is whether the difference between G and F is categorically different than B and A.


So far, it hasn't "failed". You've only asserted the contrary. Let's remember that I didn't claim that winged fight or stereoscopic eyesight was categoricallly different; I just pointed out that until one can demonstrate that they are not categoricallly different, the reasoning fails.

If walking across the country can be done by walking across town after town, then even though the difference between 1000 miles and 10 miles is great the difference between any one 10-consecutive-mile set in the 1000 miles and any other 10-consecutive-mile set is not so great; thus it is reasonable to say that both can be done by walking. The theory of evolution does not call for a leap as great as going from point A to F directly, but rather through a gradual step-by-step process, and unlike the difference between going to the moon and going across town, none of those small, gradual steps is that categorically different than the rest. For example, in reference to flying, even among the species that are currently alive right now--not counting the billions who have gone extinct--we can see a vast spectrum from those that can not fly including completely flightless birds and those that can fly best of all with many shades of grey in the middle marked by species who can glide a little to ones who fly for brief, awkward sets occasionally.


I have not challenged the evidence for common descent or the gradual change from one species to another; what I have pointed out is that Alun has not made a case that the particular process in question - natural selection - is up to the challenge, and that winged flight or stereoscopic vision isn't categorigically different from the kinds of mutations we empirically find natural selection to produce.

Unless natural selection is specifically shown, at least in principle, that it is capable of producing winged flight or stereoscopic vision, then it is not a reasonable claim - because we do not know if we are making a categorical error.

Because the wind can carve shapes in a cliff face in X amount of time, doesn't mean that it can carve the entire text of War and Peace in any amount of time, with any amount of cliff faces to work with. Just because a process can produce a variance in a material, doesn't mean that it can produce any variance, or any collection or aggregate of variances.

That is a compositional fallacy.
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Post Number:#60  Postby Alun » June 22nd, 2010, 8:44 pm

Meleagar wrote:Yes, that was my point. Until one knows they are not making a categorical mistake, then claiming that a process that can lead to one goal can accumulatively lead to the other. We don't know that the two goals are in the same category.

Obviously different cases require different explanatory content. Scientific explanation always requires empirical evidence--the argument I've given is only the general structure of the theory.
Meleagar wrote:Please support this assertion. You might begin by defining "traits", then showing what traits have been empirically demonstrated to be produced by natural selection, and what is involved in generating a trait like stereoscopic vision.

This is elementary and you had no problem with it when you read through section 2 of the OP. To reiterate, all biological evidence suggests that traits (observable characteristics of an organism) are entirely defined by the genetic information contained in DNA if it is 'read' by RNA. The conceptual argument that I made applies to anything defined by DNA in an organism. It will always be possible that some external force is evident, or that some degree of change cannot be explained by the internal mechanism suggested by the theory of natural selection, but both of these are contingent matters to be investigated empirically, not conceptual flaws in the argument.
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