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Author
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Topic: Is the DNA code universality strong evidence for evolution?
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charlie d.
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Member # 159
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posted 13. March 2003 21:02
It seems to me that it all boils down to how evolvable the genetic code really is. While there clearly is some flexibility for the occasional codon/aminoacid correspondence, evolving an entirely different genetic code in an established organism is, for obvious theoretical reasons, extremely unlikely. Thus, once organisms became settled within certain biochemical and genetic constraints, the prediction would be that chances of evolving significantly different codes would have been minimal.
Now, such constraints could have become manifest in the history of life either before or after the delineation of some major phylogenetic separation. Thus, while it is true that multiple genetic codes may not necessarily spell doom for the hypotheis of common descent, certainly a universal genetic code is a significant piece of evidence in its favor. But maybe I am missing something.
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yersinia
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Member # 324
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posted 13. March 2003 21:34
CH, your initial post was confusing "evolution" and common descent:
quote:
Evolution envisions the code arising from simpler codes (IOW, the code did not pop into existence out of nowhere). Therefore, according to evolution the code can evolve and so evolution does not require the code to be universal. Furthermore, multiple codes could have arisen via multiple biogenesis events. In addition to not requiring the universality of the code, the evolution of the code and associated machinery would not be trivial.
[...]
The situation is that evolution speculates about how the code could have evolved, and evolution does not require the code to be universal. Yet evolutionists claim the universality of the code as compelling evidence. So, what I'd like to explore in this thread is this claim. Is the claim sound and valid or is there something wrong with evolutionist's reasoning?
...but you haven't really re-stated things after you acknowledged the difference. The above quote does make sense if one simply substitutes "common descent" for "evolution". So I'm still not sure what you're arguing.
But generally:
What do *you* consider good evidence for common descent?
For example, in a criminal forensic situation, on what basis do we conclude that a sample came from a particular person? How are paternity cases decided? How was it established that Native Americans are more closely related to east asian groups than some other arbitrarily chosen group of humans?
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Cornelius G. Hunter
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Member # 81
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posted 14. March 2003 01:15
Nic and Charlie:
Nic, you ask: "What do *you* consider good evidence for common descent?"
Charlie points out that if the code couldn't evolve "once organisms became settled within certain biochemical and genetic constraints" then its universality "is a significant piece of evidence" for common descent. This seems right at first, however, I see a couple of serious problems.
First, is the premise correct? The minor deviations we find today are supposed to have evolved via common descent from the universal code. Could it not be possible that this micro evolution process could extrapolate over the millions of years to create bigger changes? Also, there is no doubt that there are a whole lot of folks who believe the code evolved from simpler codes. It is difficult to understand, nor has any detailed or convincing explanation been given for, why such a complex code and machinery can be evolved to, yet then no further such evolution is allowed. So it is not clear that the premise is so obvious.
Second, even if we did convince ourselves that the premise was true and therefore that common descent predicts and requires a single code, the evidence that there is a single code would still not justify the evolutionist's high claims vis-à-vis the evidence. This is the fallacy of affirming the consequent. Yes, the universality of the code would fail to falsify common descent, but why say it is such compelling evidence?
So what do I think is good evidence for common descent? Well, how's this:
*************
The introduction of the dingo appears to have quite rapidly caused the extinction of the thylacine, which was extinct from mainland Australia before Europeans arrived. Thylacine species persisted for tens of millions of years in the Australian fossil record, into the period of human habitation, and yet some stone-age boat people (unintentionally) killed them off by transplanting an apparently superior design, the dingo.
The only place that thylacines hung on until the 1900's was in the isolated island of Tasmania, where dingos and bounty hunters reduced their population to fatally low numbers by the 1930's.
As if this wasn't enough, this appears to be a general pattern with only a few exceptions: placentals have proven to be superior competitors for the same ecological niches, which is why there are precious few marsupials in South America (formerly an Australia-like place before the Panamanian isthmus connected it to North America), and why so many marsupials are endangered in Australia, while things like feral rats, cats, rabbits, and dogs (dingo) are thriving wildly.
By any standard of "good design", it appears that the hypothetical IDer's actions "make little sense": to carefully craft all of these marsupial species for parallel ecological niches on separate landmasses, let them be fruitful and multiply for millions of years, followed by prompt extermination once tectonic accidents or stone-age boats allow apparently superior designs to invade.
http://www.iscid.org/ubbcgi/ultimatebb.cgi?ubb=get_topic;f=6;t=000266;p=3
*************
This comes from Nic himself. Nic, you have constructed what I think is a very strong argument for common descent here. Why? Because if the species weren't specifically designed (or created), then common descent becomes by far the most likely explanation for them. By using the process-of-elimination approach, you obviate the affirming the consequent fallacy. IOW, your argument is not so much "these must have evolved" as it is "these must not have been designed or created." Not only does this not affirm the consequent, but (assuming we agree that common descent and creation are the only two viable candidates) you are now in a position to make the claim that common descent is a fact.
In fact, I have found this form of argument used for the universality of the DNA code. IOW, it is said that if the species were created they wouldn't have the same code and hence the universality of the code is compelling evidence – it proves common descent. I wonder if this is what evolutionists are getting at when they make such high claims vis-à-vis this evidence? It would explain everything.
There is one small hitch. This very powerful argument comes at the cost of making assumptions about the Creator or Designer. How does one defend such assumptions and how does one justify bringing such assumptions into science? I don't think either are possible unless they are in response to previously made claims by, for example, creationists or IDers. Hence there appears to be a thesis-antithesis relationship based on metaphysical claims.
--Cornelius
[ 14. March 2003, 02:09: Message edited by: Cornelius G. Hunter ]
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yersinia
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posted 14. March 2003 04:41
quote:
This comes from Nic himself. Nic, you have constructed what I think is a very strong argument for common descent here. Why? Because if the species weren't specifically designed (or created), then common descent becomes by far the most likely explanation for them. By using the process-of-elimination approach, you obviate the affirming the consequent fallacy. IOW, your argument is not so much "these must have evolved" as it is "these must not have been designed or created." Not only does this not affirm the consequent, but (assuming we agree that common descent and creation are the only two viable candidates) you are now in a position to make the claim that common descent is a fact.
In fact, I have found this form of argument used for the universality of the DNA code. IOW, it is said that if the species were created they wouldn't have the same code and hence the universality of the code is compelling evidence – it proves common descent. I wonder if this is what evolutionists are getting at when they make such high claims vis-à-vis this evidence? It would explain everything.
There is one small hitch. This very powerful argument comes at the cost of making assumptions about the Creator or Designer. How does one defend such assumptions and how does one justify bringing such assumptions into science? I don't think either are possible unless they are in response to previously made claims by, for example, creationists or IDers. Hence there appears to be a thesis-antithesis relationship based on metaphysical claims.
Far be it for me to criticize my own thylacine example, which I'm quite proud of, but: I made an assumption about the Creator or Designer there, also. In that case it happens that the assumption was one which most IDers appear to (at least subliminally, they won't always admit to it explicitly) adhere to, namely that the designs should be some general version of "good" (meaning high quality, lacking blatant kludges, not good vs. evil "good").
I suspect that the reason you didn't notice this assumption was that you took it for granted.
But if we're going to really not allow the evolutionists to make any assumptions about the designer(s), well then, isn't it perfectly possible that the designer just has a twisted sense of humor and had it in for large carnivore marsupials this millenium? Or maybe there were multiple designers and the marusupial designer was just more inept than the placental designer. Or maybe the designer was insane. Or maybe the weakness of marsupials was "front-loaded" into them for some higher purpose.
In fact, Mike Gene has performed exactly the above procedure. He and many IDers suggested that the mutation-repressing features of basic biochemistry were a result of good design. When an article was pointed out that pointed out that cytosine deanimation appeared to be a kind of kludge similar to the thylacine example above, did Mike Gene do what Cornelius Hunter did with thylacines and say, basically, "good counterexample"? No, he has gone and constructed a whole, very complex sub-theory that this particular mutation-increasing trait is not a kludge but a "front-loading" design feature that, via the mutation bias it imparts, leads in some still vaguely-specified fashion to a vaguely-different form of evolution than we would get otherwise. Never mind that doing any designing with a mere mutation bias seems to be rather like typing with your elbows -- that is, slow, wildly inefficient, uncertain, with a high probability of not achieiving the desired result (whatever that is) at all -- nope, Mike can conjure the whole thing pretty much out of thin air since, well, because when we're dealing with unconstrained designers pretty much anything is possible.
quote:
In fact, I have found this form of argument used for the universality of the DNA code. IOW, it is said that if the species were created they wouldn't have the same code and hence the universality of the code is compelling evidence – it proves common descent. I wonder if this is what evolutionists are getting at when they make such high claims vis-à-vis this evidence? It would explain everything.
There is one small hitch. This very powerful argument comes at the cost of making assumptions about the Creator or Designer. How does one defend such assumptions and how does one justify bringing such assumptions into science? I don't think either are possible unless they are in response to previously made claims by, for example, creationists or IDers. Hence there appears to be a thesis-antithesis relationship based on metaphysical claims.
Regarding the standard code: do we have any basis for thinking that the hypothetical designer *would* use a different but similarly optimal code? Sure, we can invent some reasons, if, say, the designer was interested in promoting lateral gene transfer. But we could just as well say that we would expect a designer to want to make his work obvious to whatever intelligent beings might result down the line, and therefore would have used many wildly different nontransformable codes to make it clear to later observers that separate origination events had occurred. IMO we have no basis to favor one over another.
However: under the hypothesis that a group of organisms are related by common descent, we would expect that the organisms would share arbitrary (=could be much different) traits via heredity. We know that the traits that are hardest to change will change the slowest.
We know that the genetic code is hard to change for anything with a large genome because switching a codon assignment would mess up any number of crucial proteins. We know that the (minor) variant codes are pretty much only found in organisms with small genomes (mitochondria, bacteria) or otherwise peculiar genomes (ciliates, which have microchromosomes where each gene can have it's own chromosome). Plus, we know of some extant organisms (some bacteria) where wobbly codon assignments exist but are not harmful. These wobbly assignments (e.g. the stop codon) correspond to the code deviants that we most commonly see in deviant organisms.
Based on all this, we would expect that if all life shared a common ancestor, things like the genetic code would be the most likely things that we would expect them to share. Thus we have an expectation based on common descent and knowledge about the code.
Based on design, we have: well, I think we have no expectation either way. So you're right, it hasn't been ruled out, we just have no positive reason to predict one way or the other.
For that matter, we should also point out that the following hypotheses have also not been ruled out:
- quantum leprechauns guiding molecular interactions so as to produce one or multiple codes
- unknown forces of the universe that bring about one or multiple codes
- that matter and energy actually have inherent intelligence and thereby brought about one or multiple codes
- etc. An infinite list of possible, not-ruled-out ghosts and goblins can be conjured by the imagination to "explain" observations in an ad hoc manner. Just within the label "ID" we could construct an infinite number of possible designers to explain any potential observation.
Cornelius, you seem to think it is the duty of responsible science to go off on an intellectual ghost-busting expedition before any conclusions can be drawn about observations supporting a specific natural-causes hypothesis (like descent with modification). But you can't slay a beast that is just a shadow.
Here is my point: what do you want science to do? Spend all its time considering conceivable actions by the universe of unknown entities lacking even a shred of positive evidence in their favor? There are an infinite number of such critters hanging out in the imagination.
Instead, shouldn't science take hypotheses that actually have some empirical implications and initial empirical support (e.g.: we see organisms reproducing) and go about testing those?
quote:
There is one small hitch. This very powerful argument comes at the cost of making assumptions about the Creator or Designer. How does one defend such assumptions and how does one justify bringing such assumptions into science? I don't think either are possible unless they are in response to previously made claims by, for example, creationists or IDers. Hence there appears to be a thesis-antithesis relationship based on metaphysical claims.
Short answer: vaguely-specified independent design doesn't lead us to expect anything in particular either way; common descent does. You can therefore have positive evidence for common descent, negative evidence *against* design is not a requirement for this to occur.
Similarly, we don't need evidence against invisible star-pushing leprechauns to conclude that the regular wobbling of stars points to the existence of extrasolar planets.
yersinia
PS: Now in actual fact, IDists of various stripes do rather often make more explicit claims about the proposed designer and his actions. These can then be tested. Strangely, however, IDists often try to disguise these more specific claims or won't admit to them. I find this strange because specificity in one's hypothesis is a great scientific advantage: it allows for expectations and testing.
[ 14. March 2003, 04:58: Message edited by: yersinia ]
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charlie d.
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posted 14. March 2003 11:51
quote:
Charlie points out that if the code couldn't evolve "once organisms became settled within certain biochemical and genetic constraints" then its universality "is a significant piece of evidence" for common descent. This seems right at first, however, I see a couple of serious problems.
First, is the premise correct? The minor deviations we find today are supposed to have evolved via common descent from the universal code. Could it not be possible that this micro evolution process could extrapolate over the millions of years to create bigger changes?
I don't think so. Changing the genetic code is very different from changing one aminoacid a a time in a single protein. The limiting factor is the functional tolerance of the entire proteome for massive aminoacid substitution. While for a single protein you can envision the progressive change of one residue at a time, or for a specific pathway the change of one factor at a time, for the genetic code progressive accumulation of changes makes little theoretical sense.
Imagine a change in the standard genetic code that in one organism generates a new codon-aa association. This appears indeed to have happened occasionally in evolution, but where do you go from there? As far as all the other codons are concerned, the new variant code is no different from the standard one, and any new change will bring the exact proteomic changes it would bring to the standard code. While for an individual protein a first neutral residue substitution may bring more tolerance (or even selective advantage) for a second change, when the change affects the entire proteome, tolerance shifts will balance out over a large number or proteins, and the second change would be just as disadvantageous as it was before the first occurred.
Furthermore, genetic code changes occur most often in highly unusual circumstances, for instance in organisms whose GC content is so skewed that certain codons become extremely rare if not entirely "extinct" (and can thus be easily "reassigned"), or, as pointed out by yersinia, those whose proteome is highly reduced (for instance, endosymbionts/parasites). Even if conditions make one or a few such code changes possible, it becomes unlikely to imagine significant additional changes accumulating, because selective constraints on abundant codons will always persist. quote:
Also, there is no doubt that there are a whole lot of folks who believe the code evolved from simpler codes. It is difficult to understand, nor has any detailed or convincing explanation been given for, why such a complex code and machinery can be evolved to, yet then no further such evolution is allowed. So it is not clear that the premise is so obvious.
I think the evolution of the genetic code is believed to have occurred in critters far simpler and more biochemically "moldable" than current ones (indeed, far more simple than the LCA, whether it was one organism or a genetically orgiastic community thereof). As for explanations, I gave a general one above that makes sense to me. There was a good recent review in Nature Genetics on the genetic code (though I am sure you've read it). quote:
Second, even if we did convince ourselves that the premise was true and therefore that common descent predicts and requires a single code, the evidence that there is a single code would still not justify the evolutionist's high claims vis-à-vis the evidence. This is the fallacy of affirming the consequent. Yes, the universality of the code would fail to falsify common descent, but why say it is such compelling evidence?
I am not sure about this "affirming the consequent" thing.
A universal genetic code is a fair and fairly restrictive prediction for organisms derived by common descent whose biochemistry is sufficiently complex to generate constraints. These constraints are and can be verified both on theoretical grounds and empirically, in the attempts to generate organisms with variant genetic codes. I think there is little doubt that msot living organisms display just this kind of contrained biochemistry.
On the other hand, the finding of many/very different genetic codes would be a prediction for either a) lack of common descent, b) common descent in which historically individual lineages separated before complex organismal biochemistry became established, or c) common descent for organisms with persistent very simple biochemistry.
Very different predictions, very different observations, very different inferences.
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Cornelius G. Hunter
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posted 14. March 2003 12:40
Nic:
I enjoyed and agree with much of what you say, but need to clarify a few things. You write:
************ Nic wrote:
Far be it for me to criticize my own thylacine example, which I'm quite proud of, but: I made an assumption about the Creator or Designer there, also. In that case it happens that the assumption was one which most IDers appear to (at least subliminally, they won't always admit to it explicitly) adhere to, namely that the designs should be some general version of "good" (meaning high quality, lacking blatant kludges, not good vs. evil "good").
I suspect that the reason you didn't notice this assumption was that you took it for granted.
************
I was surprised that you thought I didn't notice your assumption. I thought I made it clear that that was my point; ie, you have a powerful argument, but it comes at a cost. Did you know that William Paley wrote that the basis of his whole scheme was that "God wills and wishes for the happiness of his creatures" ? It was, in fact, a consistent theme in eighteenth century English natural theology. Nature was expected and viewed as being perfect and harmonious. People like Hume and Darwin had a field day with this. We are seeing the same thing today with ID and evolution.
All the strong arguments for evolution, laid out by Darwin, and subsequently advanced by evolutionists up to today are of the form of your thylacine example. Strip evolution of its metaphysical arguments and you are left with rather ambiguous and even negative evidence. (fossils that appear planted there, adaptation mechanisms that are highly complex [ie, evolution must have created an small-scale evolution machine], fossil patterns that do not support the idea that small-scale change extrapolates to large-scale change, many examples of similarities that must have arisen independently even though contingency is supposed to dominate necessity, etc. etc.).
You stated in an earlier post that the DNA code deviations follow a phylogenetic pattern, but in fact this does not seem to be the case. Ken Miller tried to make this point but it made no sense. The DNA code variations are scattered across various types of organisms. For example, the UAR codon is observed to switch from "stop" to "Gln" in green algae, various ciliates, and some diplomonads. Likewise, the UGA codon is observed to switch from "stop" to "Trp" in other various ciliates and two firmicutes. Perhaps this confusion arose because Knight* used a diagram to illustrate the distribution of the deviations and the diagram, if one doesn't look at the details, kind of looks like a phylogenetic tree – it isn't.
*Knight, D.R., et. al., “Rewiring the keyboard: evolvability of the genetic code,” Nature Reviews-Genetics, 2:49-59.
You wrote:
********************* Nic wrote:
Cornelius, you seem to think it is the duty of responsible science to go off on an intellectual ghost-busting expedition before any conclusions can be drawn about observations supporting a specific natural-causes hypothesis (like descent with modification). But you can't slay a beast that is just a shadow.
Here is my point: what do you want science to do? Spend all its time considering conceivable actions by the universe of unknown entities lacking even a shred of positive evidence in their favor? There are an infinite number of such critters hanging out in the imagination.
Instead, shouldn't science take hypotheses that actually have some empirical implications and initial empirical support (e.g.: we see organisms reproducing) and go about testing those?
*********************
You're misunderstanding me a bit. Science is a complicated thing that is hard to describe, and therefore hard to place limits on. Just what is science? One thing is clear, a great many scientists have used liberal metaphysics in their theorizing. Evolution is an outstanding example of this (you are arguing that ID is too). I'm not (necessarily) saying this should be outlawed. Nor am I arguing here that evolution is false. I certainly see it as a very powerful theory. But all its power comes from metaphysics. This is why it is called a fact. It is a fact because the alternatives have been refuted.
One would never say a scientific theory is a fact because its predictions have been observed. This is a blatant fallacy of which I have never seen evolutionists guilty of. Instead, it is a fact because evolution interprets nature as having falsified creation (Darwin: "The several subordinate groups in any class cannot be ranked in a single file, but seem clustered round points, and these round other points, and so on in almost endless cycles. If species had been independently created, no explanation would have been possible of this kind of classification," this is one of a multitude of examples).
This sort of reasoning is fundamental to evolution. Hence, the "fact of evolution" is also fundamental. If you don't agree evolution is a fact, that necessarily implies that you do not agree with its fundamental reasoning. The "fact" of evolution is part and parcel to the theory itself. Check out, as a typical example, SJ Gould's piece** on why evolution is a fact. All of his evidences and arguments are metaphysical.
**http://www.freethought-web.org/ctrl/gould_fact-and-theory.html, Evolution as Fact and Theory (from Hen's Teeth and Horse's Toes, 1994)
Sooo, do I want science to spend all its time considering conceivable actions by the universe of unknown entities? Of course not. What I do think scientists should do, however, is to clearly lay out all the metaphysical assumptions. Instead of claiming to be free of religious influence, let's drop the pretense and own up, as you have so admirably here. Evolution is a fact because it makes metaphysical assumptions which rule out creation. As such, it is contingent on religious assumptions. I wouldn't argue evolution if false anymore than I'd argue that Buddhism is false.
--Cornelius
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Cornelius G. Hunter
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posted 14. March 2003 12:43
Charlie:
You wrote: "I am not sure about this "affirming the consequent" thing."
Example: Ptolemy predicted an ecclipse using his earth-centered system. The ecclipse occurred. If you then conclude Ptolemy's theory is correct and the earth is the center of the universe, then you are affirming the consequent.
--Cornelius
[ 14. March 2003, 12:44: Message edited by: Cornelius G. Hunter ]
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charlie d.
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posted 14. March 2003 14:18
quote:
Cornelius:
Evolution is a fact because it makes metaphysical assumptions which rule out creation.
Your argument is rather forced. I'd say that evolution is a fact because it is consistent with an enormous amount of empirical observations, with no contrary evidence. Indeed, it is a fact, just like gravitation or the existence of subatomic particles, because it has such evidentiary support that at this point it is almost inconceivable that contrary evidence will ever be found.
The only role metaphysics has in this is dependent on the use of metaphysics by evolution opponents. For instance, the fossil record is consistent with evolutionary theory on its face (biological types appear and disappear in time in an ordered fashion, transitional forms are common, etc), however, if the objection is brought that fossils may have been planted there purposefully by a divinity, or that a divinity may have created and destroyed biological forms at whim during the planet's history, it is entirely legitimate to bring up the metaphysical issues raised by the modus operandi of such a divinity. Evolution does not depend on such metaphysical arguments, though, but on the value of the empirical record.
As for Darwin, I don't even think it's fair to categorize his references to creationism as truly metaphysical in nature: he compared creationism to his own theory (that aimed to explain biological diversity as the product of evolution by natural selection) because creationism, in its many forms, was at his times a dominant - in fact the dominant, in some scientific circles and certainly among the public - scientific theory for the explanation of biological diversity.
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Cornelius G. Hunter
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posted 14. March 2003 15:06
Charlie:
You wrote:
************
Your argument is rather forced. I'd say that evolution is a fact because it is consistent with an enormous amount of empirical observations, with no contrary evidence. Indeed, it is a fact, just like gravitation or the existence of subatomic particles, because it has such evidentiary support that at this point it is almost inconceivable that contrary evidence will ever be found.
************
This statement is quite relevant to this thread. Although I introduced the thread using the universality of the DNA code as my example, my point was that it was merely an example, and the real question I wanted to explore was the high claims of evolutionists in the face of ambiguous evidence (as exemplified in the DNA code argument).
So, when you say "evolution is a fact because it is consistent with an enormous amount of empirical observations, with no contrary evidence" this is really exactly what this thread is about. How is it that you and evolutionists come to these conclusions? On the face of it, your statement has several problems. I'm sure you are aware of these, and so I'm wondering how you come to your conclusions.
Obviously, there is plenty of contrary evidence and evolution is not a fact. One example from this thread is the existence of the DNA code (universal or not). Obviously evolution has only speculation about how it would have arisen. You also noted the empirical fact that many fossils appear fully formed, planted there in the fossil record. How is this not "contrary evidence"? Obviously we could go on and on about contrary evidence, as there is plenty. I could fill pages with contrary evidence, it comes out all the time.
What I'd like to understand, however, the reasoning behind the high claims. I am not picking on your statement, as it is quite typical. One hears this all the time, but why?
You wrote: "Evolution does not depend on such metaphysical arguments, though, but on the value of the empirical record." But it is precisely those metaphysics which convert that empirical record into supporting evidence. How, then, can it be that evolution doesn't depend on metaphysics?
--Cornelius
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charlie d.
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posted 14. March 2003 15:32
Cornelius:
if we had never even heard of the Bible, or any other creation story, or of any God whatsoever, the fossil record would still be evidence supporting the idea that life forms appeared, disappeared and changed according to certain patterns during the history of this planet - which is what evolution (the fact) is all about. I don't see how you can argue otherwise (unless you want to introduce a metaphysical stance - but then I would be authorized to argue metaphysics too).
[And incidentally I never said that fossils "appear fully formed, planted there in the fossil record" - in fact I said that, as predicted, transitional forms are common. The "planting" argument I referred to was a creationist argument - and includes the planting of intermediate forms.]
It now seems clear that your goal with this thread was not to discuss the genetic code and its evolution/evolvability, but the old canard about the metaphysical nature of evolutionary theory.
Anyway, to go back to the original empirical issue: evolutionary theory makes specific predictions about whether the genetic code would or not be universal, depending on various considerations about extent and pattern of common descent, biochemical/genetic constraints, and historical contingency. It so happens that the existence of a universal genetic code, together with some theoretical considerations about code optimization etc, strongly supports certain evolutionary models, including universal common descent.
If you'd like to argue why it is (or shouldn't be)so, from a non-metaphysical standpoint, give it a shot. Otherwise I don't see really what we should discuss.
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Cornelius G. Hunter
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posted 14. March 2003 16:05
Charlie:
I merely want to do is understand better what you are saying. When you say the fact of evolution has to do with the changing fossil record you seem to be reducing evolution to merely "change over time" regardless of mechanism. If this is so, then of course, evolution is a fact, no problem. But in your other statements I sense you are not restricting the word "evolution" in this sense. It sounds like you are saying evolution as we colloqially understand it (ie, Darwin's theory).
You seem to be denying that fossils appear fully formed in the record. Your implication is that it is a bogus argument advanced by creationists with a religious agenda. But surely you are aware of the Burgess shale finds, as just one example. The general problem of rapid appearance followed by no change was a conundrum for paleontology for much of the twentieth century. The result (or a result) was the subhypothesis of punctuated equilibrium, which was really nothing more than Huxley's original view that evolution should not be limited to gradualism. Had Darwin gone that route evolution likely wouldn't have caught on. But by the 1970s evolution was considered to be a fact, so more radical subhypotheses could then be introduced.
You wrote: "It now seems clear that your goal with this thread was not to discuss the genetic code and its evolution/evolvability, but the old canard about the metaphysical nature of evolutionary theory."
I tried to make it clear in the IP, and throughout this thread that my goal is in parsing out / understanding the logic and reasoning behind evolution's high claims about the evidence. The genetic code's evolvability was not the main point.
Your wrote: "It so happens that the existence of a universal genetic code, together with some theoretical considerations about code optimization etc, strongly supports certain evolutionary models, including universal common descent. If you'd like to argue why it is (or shouldn't be) so, from a non-metaphysical standpoint, give it a shot."
We've already gone over in previous posts the fact that common descent does not require a single code. And furthermore, even if it did, it would not essentially prove common descent as is claimed. We've also talked about the fact that the universality of the code is very nicely explained by common descent. The question is, where do the high evidential claims come from, either vis-à-vis the universality of the code, or more generally, your claims in that evolution is a fact and there are no contrary evidences.
The point here is not so much to get into the scientific details of how evolution or common descent might explain or predict this or that (though that may be important in some cases), but to clarify the thinking behind such claims as evolution is a fact, there are no contrary evidences, the universality of the code is compelling evidence, etc. These statements are so contrary to what one typically finds in science that I think it is important to understand them. What is the underlying reasoning and logic?
At this point, however, I think it would be helpful to narrow the discussion. How about this: could you please lay out, in step-by-step fasion, how you conclude (i) that there are no contrary evidences for evolution, or (ii) that evolution is a fact. If you could pick one (or both) of these and include all assumptions and definitions, then that would explain what I'm asking.
--Cornelius
[ 14. March 2003, 18:33: Message edited by: Cornelius G. Hunter ]
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yersinia
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posted 14. March 2003 20:09
Cornelius,
You're shooting this thread off in a zillion directions. Your statements about transitional fossils, punk eek, the alleged non-derivedness of the deviant genetic codes, and challenging us to show that evolution is a fact would all take their own very long threads. If you'd like I can cite the relevant talk.origins FAQs for most of these.
What you haven't explained, however, is *why* shared standard code is not good evidence for common descent. You've asserted it over and over but I haven't seen an argument. We've explained (briefly) why the code would be expected to be difficult to change once established in large genomes, and therefore concluded that it would be very conserved in a process of descent-with-modification, and therefore the existence of this universally shared character (standard code or slight derivatives) is evidence for the action of said process of descent with modification. You haven't shown that there is any arbitrary metaphysics in that chain of argument. It's essentially the same argument that we use to conclude that person X not Y is the father of child Z in a paternity dispute.
Or do you see metaphysics in paternity disputes, also?
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yersinia
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posted 14. March 2003 20:17
PS: It would also be nice if you would give a brief outline of a *positive* model of the way you think science should be operating -- in general, or in the specific case of the question of common descent.
I don't think it can be done if you are supposed to take seriously every conceivable metaphysical process that the imagination can conjure up.
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Moderator
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posted 14. March 2003 20:35
My suspicions were confirmed regarding the direction of this thread. Calls for "evidence of evolution" just don't belong here. Also, the whole process of intentionally trying to set-up someone or a group of people is a red flag to the Brainstorms moderators.
This board is not just another stomping ground for beating up on your favorite (or least favorite theory). Collaboration, respect, cooperation and a real interest in moving the discussion forward are what we want.
Again, I suggest the postings of Mike Gene and Art as exemplary examples of two posters who disagree but respectfully and productively engage.
[ 14. March 2003, 20:41: Message edited by: Moderator ]
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