Has evolution been proven ?

Actually, this isn't a bad exercise. However, it might be more appropriate to examine a basal crossopterygian (lobe-fin fish) and a basal tetrapod, rather than modern salamander.Let's see if this image works: Note the close resemblance between the structure of the lobe-fin's limbs (from a modern Latimeria chalumnae skeleton) and a tetrapod (from, I think, an Ichthyostega stensonioei). The amphibian's bones are a bit larger, but all of them have a close (like, one-to-one) correspondance with the bones in the crossopterygian. Since the "modifications" were minor, there's no apparent reason why darwinian processes couldn't have made the tetrapod from a fish. Gee, it sure looks like the concensus scientific opinion is right that "fishy went a-walkin'" back in the Devonian, and the ones that did were lobe-fins.

Hi Denesha,Welcome to evcforum! Hope you enjoy your stay. If English is a second (or more) language, then feel free to ask for clarification of something someone writes - most of us are willing to explain. Here's an example of a language problem. In English, scientists seldom talk about "proof", because the connotation is "mathematical certainty" - something that science simply doesn't have. It's better to talk about "evidence", in which case your statement would be completely correct. The evidence for evolution is pretty convincing, IMHO. edited 'cause even in English I can't spell...[This message has been edited by Quetzal, 03-15-2004]

I don't disagree with you Mr. J. Scientists, even in the "hallowed pages" of peer-reviewed journals, often mention "proof" of something or other. However, I would argue that when they use it they are considering they're talking to other scientists - and with the tacit understanding that science by definition is never proven in the absolute sense. My real quibble is that when you transfer the term to a place like EVCforum, or other debate arena where the creationists try and conflate Proof in the absolute sense with proof in the colloquial sense, it behooves us to be scrupulous in how we use the word. Because the entire creationist assault on evolutionary theory is based on equivocation and semantics, we have to avoid falling into the trap. We need to continually make explicit what is implicit in scientific discussions.OTOH, just 'cause they're highly educated scientists doesn't mean they can either spell or use words correctly. You have NO idea how many times and how much effort was required to re-write my partner's scientific reports just to make them marginally comprehendable. And this is a PhD evo biologist with a long string of articles to his credit. Sheesh, but he was a TERRIBLE writer.

How very odd. I'm usually much better at interpreting someone's point. I thought the exercise was designed to show dissimilarity between fish and amphibian. The comparison between the Latimeria skeleton - a free-swimming fully fishy fish - and Ichthyostega, a partially land-dwelling/walking amphibian would show that the similarities more than outweighed the differences. In fact, there's a water-dwelling intermediate between the crossopterygians and the amphibian I showed (Acanthostega) which demonstrates even more clearly the similarities - it even has a fishy tail along with its legs. I couldn't find a decent picture (see Mark24's avatar for one).I think the major problem with your excercise was that you appeared to be comparing apples and oranges - the fish description you gave was of an actinopterygian ("ray finned"). The ray-fins are what we normally think of as "fish". However, since actinopterygii aren't considered to be on the branch leading to tetrapods, comparing the two is meaningless. IOW, you're absolutely right - comparing a ray fin to a salamander shows there's little likliehood the one could have evolved into the other. However, that's not the lineage. As to the survival issue, I'm not sure I understand what you're asking for. Why would there be any problem with the gradual reshaping of an already existing structure like the crossopterygian fin-leg - which contains in miniature all of the bones required of a tetrapod - via natural selection? It didn't happen overnight - a gradual lengthening and reshaping of the limb, pelvis, etc, over thousands of generations wouldn't pose any survival problem that I'm aware of. In fact, I can think of quite a few advantages, for instance to allow its possessor to better take advantage of shallow or estuarine habitats, or to be a better bottom ambusher, or to move between drying lakes and whatnot during the Devonian drought, etc. Perhaps you could elaborate as to why you think there would be a net fitness disadvantage? Or perhaps elaborate your central argument more fully to insure I don't misinterpret what you're after again?

Hi BAE, About the only way you're going to get the detail you need on the bones issue is to get a copy of one of the textbooks that deal at that level. My personal favorite is Caroll's "Vertebrate Paleontology and Evolution" (WH Freeman, 1987), although that's preference born of familiarity rather than any specific "this 'uns better than that 'un" analysis. It's also a bit dated and he doesn't seem to like cladistics very much (I want to get Caroll's newer "Patterns and Processes of Vertebrate Evolution").On the other bit about salamanders, I have some notes that I'll dig out and post (probably this afternoon if I get a chance) that cover the concensus phylogeny (evolutionary lineage) of modern salamanders - although you again need to remember that salamanders are NOT tetrapod "ancestors" or even necessarily representative of the basal tetrapod lineage. They are descendents of this ancestral form, just like every other amphibian on the planet including frogs etc., and include IIRC some 10 living and 4 extinct families of organisms in the Order Caudata (or sometimes called Urodela). That's not only a lot of critters, but it represents a lot of critters with vastly different morphologies - from newts to sirenians to true salamanders to hellbenders.If you want a more appropriate group of critters to research for your comparison, I would suggest the Dipnoi (lungfish). These little guys are some of the last living descendants (along with the Coelacanthinae) of the crosspterygian lineage - the critters that went walking. Comparisons are great - but make sure you're comparing the right things.I'll be happy to wait until you've done some more reading. I would, however, appreciate it if you'd address the points I raised in this and my previous post when you're ready.

You'll enjoy it Mark. Knoll's a great writer, and he presents an easily understandable review of what's known about the first 3 billion years of life on Earth. I really liked it.

No worries. I totally agree with what you said. TV and popular books often either overstate the case or go for the visual effect. I'm not against "dumbing down" concensus science to make it understandable and attractive, but this is often carried to far. You should see my wife and I yelling and throwing popcorn at the TV when my kids watch the PBS series "Walking with Dinosaurs" . (My kids love it, but my wife and I are shouting things like, "And you know this how exactly?" or "That's an unwarranted extrapolation you boobs".) A fun time is had by all. Great! They're both good, but I'd suggest the newer "Patterns and Processes". A lot of additional, more recent info is included. Hope you enjoy it, even if you don't accept the conclusions. Well, we certainly appear to be discussing the neodarwinian evolution idea, but I'm not sure I agree with the second part of your statement. If you'll refer to the last paragraph of my post #21, I think you'll see that I don't consider the gradual transition from crossopterygian fin-limb to tetrapod limb to be very problematic under that paradigm. In fact, if you go a bit further back in time to some of the earlier rhipidistian fish (from which the crossopterygians were derived), you'll see that even the "first stage" doesn't appear very difficult. See if you can find a picture of first, a Eusthenopteron and then a Panderichthys, and then look again at the Latimeria skeleton. Note as well that, although I suggested the Dipnoi, the living species of this family really don't have the right fin structure, so I retract my comparison suggestion. The closest living organism we can come at that may illustrate the transition from the rhipidistian fish to tetrapods is the coelacanth - but it wasn't THE transitional. That honor is reserved for the Eusthenopteron - Panderichthys - Acanthostega - Ichthyostega transition. By the time you get from the first to the last, you've gone from free-swimming fish to a fully-formed basal tetrapod with all the adaptations necessary for at least waddling about on dry land (I doubt it'd be winning any marathons). The transitions are in the nature of small, gradual adaptations over millions of years - from the early Devonian of Eusthenopteron to the Late Devonian of Ichthyostega.Hope this clarifies my position.

Yep. Yer preaching to the choir, Abby.

Well, I'd say unless you have some particular desire to buy the books, you should be able to get both from your uni library - they're pretty much standard texts. Looking forward to your reply when you're ready.

Obviously, I agree with you that observed speciation and genetics pretty conclusively show beyond reasonable doubt that evolution has occurred, as do mutualisms and other symbioses, predator-prey relationships, antibiotic and pesticide resistance, community assembly, biological succession, etc. None of these by themselves "prove" anything. It's the accumulation of these completely independent lines of evidence that lead inexorably to the same conclusion that makes evolutionary theory so robust.Unfortunately, in general that's not the creationists' argument. They will confidently proclaim that all the examples you'd care to give of speciation don't represent macroevolution (hence mangling the terminology for their own ends). So it is necessary when arguing with them to show that the predictions of evolutionary theory (or if you prefer, retrodictions) have been borne out. The only way to do that is to reference the historical record of life on Earth - the fossils. In spite of its terrible patchiness, incompleteness, and highly skewed distribution (i.e., many more easily fossilizable marine organisms than land animals, etc), the fascinating fact is that what we do have fits perfectly into the evolutionary framework. We CAN predict that, if swimmers became land critters for instance, we should find fossils of the 'tween organisms that show this transition - and we have.I don't think it's a futile argument, except in the sense that just about any argument with a True Believer (tm) is futile. It is, literally and in a nutshell, the route that was taken by scientists in the present and past to derive the theory of evolution in the first place.

It truly beats the hell out of me. No matter how many times I've posted or read someone else's post where the evidence - right there in front of their eyes - is presented to a creationist to no effect. I was convinced that evolution was the best explanation for the diversity of life by my own observations of nature. The framework of the TOE provides the sole best available explanation for what we see all around us. Populations change at both the microscale and macroscale. No one who isn't blind, IMO, would be able to deny it with a little effort at getting out in the field and LOOKING. So if you can figure out why they ignore the evidence of their own eyes, let me know. It is really beyond my comprehension.The fossil record is really only necessary to demonstrate that what we see today operated in the same fashion millions of years ago. I don't disagree with you that fossils "don't prove evolution". The record of past life is simply one more - independently derived - line of evidence in favor of the theory. A strong one, perhaps, but the 25 species of Tenrecidae on Madagascar or the mutualistic relationship between Acacia acacia and Pseudomyrmex spp, provides as good.

On the other hand, what evidence - other than an individual's subjective feelings, which are unreplicatable - exists that allows a person to differentiate between the two explanations? You and I can easily go out in the woods, or to an isolated archipelago, or to the fossil-rich badlands of western North America or southern Africa, and literally touch with our own hands and see with our own eyes the facts of nature and the diversity of life. How does "godidit" provide a better explanation of what we see than the ToE? What piece of evidence, or line of evidence, explains the myriad of utterly independent lines of evidence that all lead to the same conclusion? Remember, you not only have to show that natural processes provide an insufficient explanation for the facts, but show how a supernatural process actually manifests itself to the exclusion of natural processes if you're going to make the case that God is a valid alternative. Otherwise, you're falling back on a weak "god of the gaps" and "argument from personal incredulity". I don't "dismiss" the supernatural explanation. If it could be shown that completely arbitrary discontinuities existed that could not be explained (not "haven't been explained yet") by current theory, then I'd drop it like a hot rock and start looking for other explanations. Unfortunately for the True Believer (tm), such discontinuities have not been shown to exist. Indeed, special creation was the reigning paradigm for almost 1500 years, and was reluctantly abandoned when the evidence started accumulating that it didn't, in fact, explain the observations. Many of the most brilliant naturalists of the late 18th and early 19th Centuries expended considerable effort to reconcile special creation with the mounting evidence unearthed during the Age of Exploration. Many of them, like Lyell and Wallace (among many others) remained uncomfortable with the evidence to the ends of their days - but were honest enough and had enough integrity to admit that ideas of special creation and a young Earth were incompatible with what they themselves saw.As to "perfect evidence of the existence of God", I think you should post it. You'd literally be the first in recorded history to do so. However, that discussion would not be appropriate for this thread, and it's quite unlikely that I would argue with you about it - I find metaphysics and philosophy to be about as interesting as watching paint dry, and have come to the conclusion that arguing about the existence or non-existence of a particular deity is tantamount to arguing over the square root of a duck - pointless in the extreme. OTOH, if you can demonstrate the operation of the supernatural by referring to concrete, repeatable, physical manifestations, then I'd be happy to join in. Show us the evidence that the supernatural explanation trumps the natural explanation. LoL. Sorry, I'm not laughing at you. Your statement about back-patting just struck me funny. You've obviously never been to a symposium where a controversial detail of the ToE has been dissected. Read up on the history of MacArthur/Wilson vs Lack vs Whittacker, or PE vs Gradualism (Dawkins/Dennett vs Gould/Lewontin et al), or Margulis/Sagan/Lovejoy vs the world. Backpatting is about as far from what occurs as I can conceive of. In any case, I DON'T accept the ToE as the current best explanation for the diversity of life because of its "popularity". I accept it because I have literally spent years "in the field" making my own observations. I consider it the best explanation because it does - explain what I have seen, that is. The ToE provides a coherent framework for understanding everything I've observed and pondered over from community succession to species diversity in heterogenous rainforest to plant-insect symbiosis to ecosystem and metapopulation dynamics. I can identify keystone species in a fragmented habitat - and make a prediction on minimum viable preserve size - based on the evolutionary relationships between the components. It allows me to rationally determine the likely outcome of ecosystem disruption. It lets me predict the potential cascade effect of the loss of one or more components of a natural community. It allows me to understand extinction with an eye to preventing it. The list is endless as to what can be derived from application of the theory.How can reference to the supernatural or divine intervention or even the existence or not of a deity do the same? And how does it do it better?Edited to change Denton to Dennett - hey, they both start with "D", gimme a break - and a couple of stupid typos.[This message has been edited by Quetzal, 03-30-2004]

Really? I think it would be fascinating to hear you expand on the facts that would lead one to believe that the scientific theory of evolution, in all its details, is a philosophical or metaphysical belief system. What part of sexual selection, or shared retrogenes, or say, biogeography is metaphysics? Since you obviously have such a depth of knowledge about evolution, I'd love for you to clarify these questions. Looking foward to your response. Yep, except I'd say it's more like a belief system that is used to fold, spindle, distort, or otherwise mutilate the evidence developed by science to fit a pre-conceived worldview. And the direct evidence in the trees, rocks, and living organisms for creation ex nihilo is what, exactly? Please be specific. Erm, no. It's not a presupposition. The evidence of both living and extinct organisms leads to the conclusion. Except for the bit about vertebrates giving rise to ape-like creatures and ultimately humans, since the latter two ARE vertebrates. And the fact that the lineage of vertebrates diverged from the stem metazoan lineage about the same time the invertebrates did so - that's pretty far down at the roots of multi-cellular life. Invertebrates (as we understand the term today) likely didn't "give rise to vertebrates" (note the spelling, btw). Be that as it may, the point is that this was a conclusion based on evidence uncovered over several centuries. It was not an interpretation of the evidence - the evidence led to the conclusion. Unlike creationism, where the conclusion is known and the evidence rejected or accepted on the strength of how closely it adheres to the pre-determined conclusion. As you yourself stated: Talk about projection. Again, no. It takes no faith at all to accept the ToE. It takes, perhaps, substantially more thought to understand all of its ramifications - although the folks that spend a lifetime becoming biblical scholars or theologians have probably expended as much. OTOH, I agree that all it takes is faith - without even the necessity of reflection - to reject the evidence of the senses in favor of an ancient myth which wasn't even intended for that purpose. Of course, that's not faith in God or even Christianity so much as it is unquestioning faith in a badly translated book whose original sources are lost to antiquity. Now THAT I agree with wholeheartedly.

Hi BAE, Hmm, I think you may have misphrased this (i.e., believer vs non-believer's feelings). However, I understand what you're trying to say. I tend to disagree. The key point here being that evolution, as a scientific theory, IS NOT and CAN NOT be based on feelings. Feelings are subjective, unique to an individual, non-concensual, un-repeatable, and inherently unfalsifiable. Evidence based on subjective testimony (i.e., an attestation of feelings on a subject) is not sufficient to prove the validity or invalidity of a non-subjective claim. IOW, you can't use it to argue against science - any science. It's not a question of evolutionists believing or not believing your claim to a subjective experience - it's that these experiences cannot be used in a scientific discussion. Period.Where the problem derives with what you stated is that you seem to be proposing that there is in fact objective criteria to judge subjective experience. In your case, you have stated that your belief in God has the same objective, empirical support as a scientific theory (evolution). This is basically a contradiction in terms: since "association with God" is an intensely subjective and individual experience (witness the myriad of differing interpretations of God amongst believers), it is not possible to introduce such belief or association as objective evidence. OTOH, if you were to provide physical, repeatable, (i.e., objective) evidence of the existence of God or at least valid and repeatable empirical evidence that such a being has manifested itself physically, then and only then would such an entity be "allowable" in a scientific discussion. Where are the fingerprints of God? Again, I disagree. Evidence - the data or facts of nature which are all around us - aren't going to change simply because our explanations for those facts are different. However, in evaluating those facts or in producing the inference to the best explanation, certain fundamental procedures must be adhered to by both sides:1. Our explanation must be falsifiable. We MUST be able to come up with a way to show that our idea is wrong. I know that's kind of counterintuitive, but what it means is that if our idea is false, then there conceivably can be evidence discovered that will prove it false, and if the idea is true, then the available evidence will not DISPROVE it. Consider: if nothing could ever disprove an idea or claim (the invulnerable claim), then whatever evidence DOES exist wouldn't matter - it would be pointless to even look at the evidence because the conclusion is already known.I've seen many creationists routinely violate this principle. There are two basic ways in which this happens:a) they make an undeclared claim (an assertion so broad, vague, or ambiguous that the assertion lacks any real content) such as "only with the eyes of the spirit can God's handiwork be seen". What is spirit? How do spiritual eyes work? How does a non-coporeal entity process light in the first place? What IS God and how would I know it when I see it? Etc.b) they use a "multiple out" (basically an inexhaustable series of excuses or ad hoc rationalizations to explain away contrary evidence or the lack of supporting evidence for their ideas). The "anticreationist scientific conspiracy suppressing creation science" is a prime example. There is literally no way to falsify a multiple out: the reason there is no evidence supporting the idea is that "they" are suppressing it. Heads I win, tails you lose.2. The evidence offered in support of our ideas must take into consideration all available evidence. IOW, no cheating: you can't take into consideration ONLY that evidence which seems to support your idea. ALL available evidence must be taken into account, and our idea MUST explain ALL the evidence. If neither idea can explain everything, then the one that explains the most with the fewest assumptions wins. That's how science works - this isn't a courtroom, where evidence can be manipulated and distorted to suit the preconceived conclusions of either the prosecution or defense. Nor can one side win on a technicality. By all means, interpret the evidence as you will - just be prepared to be hoist by the comprehensiveness petard.3. Evidence offered in support of our ideas must be evaluated without self-deception. Again, no cheating: if there exists evidence which contradicts the idea, then you have to be willing to abandon it. This is hard to do - people will do almost anything to avoid challenging cherished beliefs (denial, avoidance, rationalization, etc). Scientists aren't any better than anyone else in this regard - which was the basis of Kuhn's "scientific revolution" philosophy (btw, I think Kuhn was wrong: scientific progress doesn't normally happen through paradigm-bending "eureka" moments that are only accepted after all the adherents of the old paradigm are dead and buried. Rather, scientific progress normally occurs when some scientist is puddling about in the lab or walking through a rainforest and says, "Now that's odd. I wonder..." But I digress.) However, science has a built-in filter that corrects for this problem called "peer review". It doesn't mean that an individual scientist will necessarily abandon a pet theory when the evidence proves them wrong - see cold fusion for example. It means that the idea is going to have to be modified to reflect reality before being accepted.4. An independent observer, under the same conditions and circumstances, must be able to achieve the same results. If I correctly predict the next roll of a pair of dice, you need to demand that I repeat the feat before accepting that I can predict the future. Alternatively, if a phenomenon can be the product of a coincidence, the phenomenon must be replicated by someone else under the same conditions before coincidence can be rejected as an explanation. If coincidence IS the explanation, then the results will not be replicated. This especially harks back to your God hypothesis. If you claim God manifests in such and such a way, then the produced phenomena MUST be repeatable or observable by someone else - or many others - under identical conditions OR the phenomena produced for you must be considered coincidental and is invalid to use as evidential support for the hypothesis. See the problem?5. The evidence offered in support of our ideas must be adequate to establish the truth of the idea - the Rule of Sufficiency. There are a couple of parts to this bit:a) the burden of proof for any claim lies on the claimant. The absence of disconfirming evidence is NOT the same as presence of confirming evidence. It is invalid to demand that I disprove the existence of God, for example. Belief in the validity of a claim can't be based on the absence of negative evidence; only on confirming evidence. It is the claimant's responsibility to provide that evidence.b) extraordinary claims require extraordinary proof. I know this is kind of trite, but consider: if I claim that it rained today where I live, you could probably accept that claim as true (I'm in the northeastern US, it's the end of March, it often rains here this time of year). However, if I claim I was abducted by aliens and taken to the far side of the moon for bizarre medical experiments, you would be justified in demanding some additional evidence. My testimony, sufficient for the ordinary claim of rain in March, is not sufficient for the extraordinary alien abduction claim. The same thing works for the God hypothesis: the existence of a non-material, non-corporeal entity that is eternal and exists outside of the universe-as-we-know-it, is an extraordinary claim. Additional evidence of this entity's existence is required before it can be accepted as an explanation for anything.c) evidence based on testimony and/or recourse to authority is not sufficient to prove the truth (or falsehood!) of an idea. Basically, humans are fallible. Leaving outright fabrication aside, "expertise" is not a guarantee against mistakes. A person's credentials, knowledge and experience cannot, in and of themselves, be taken as sufficient evidence to establish the validity of an explanation. Eyewitness testimony is also exceptionally problematic, as any cop or trial lawyer will tell you. Single source testimony is even worse. Even if a lot of people think they see the same thing, I would be hesitant to accept an extraordinary claim on this alone. There is simply too much chance for error and collective delusion.So, bottom line: if both sides can examine the available evidence, and meet all of these criteria with their explanations, then we truly DO have two choices that come down to worldview. Care to take a stab at it? I'm not sure this is the case. Don't conflate disagreement over the details of evolutionary theory (arguments over relative importance of mechanisms, different cladistics, lumpers vs splitters, mode and tempo, the validity of molecular clocks, etc) with the fact of evolution: populations change over time, and with deep time, populations can change radically. There is literally zero disagreement over the fact that evolution has occurred among relevant scientists, and very little over the fact of common ancestry (which ancestor is which is another story). Contrast that with the gulf of opinion between ID, pantheistic creationism, YEC, OEC, etc. You may need to expand on this a bit before I can comment - I'm not sure I understand what you're getting at. What portions of the ToE are untestable (i.e., unscientific)? You might also explain what you mean by test - I think we may be talking about two different interpretations of what constitutes a valid scientific test. I think it would be great if we could come up with "necessary and sufficient" general arguments. It would save a lot of time. Perhaps we can use my five evidential criteria as a starting point? As to the potential falsifications, sure we can probably come to something of a general agreement on what would constitute a falsification of the ToE if found, but can we come up with something that would be a falsification of God if found? And if so, would you accept it? Oh, I don't know. Anyone that came up with a glaring error in the theory would be in line for the Nobel. As far as being persuaded, I won't lie to you: it would have to be pretty persuasive evidence to overturn a key feature of biology like evolution. You'd be turning the entire science upside down, because the reigning conception for the last 50 years or so was summed up by Dobhzansky: "Nothing in biology makes sense except in the light of evolution." That's not dogma, that's a statement on the nature of the problem faced by creationists. If you're going to overturn all of the biological sciences (note the plural), you're going to have to come up with something pretty fundamental to the theory that's wrong.Personally, I don't see that there's a single weak point that would topple the whole edifice unless it was something on the order of showing inheritance doesn't work the way we think it does, or that the Earth really IS only 6000 years old, or that teleological adaptation is more important that natural selection, or somesuch. However, the ToE is built up by literally thousands of independent, converging lines of inquiry from totally separate disciplines that ALL lead to the same conclusion. Your falsification of evolution will have to address each of them, I would think. Or at least come up with an alternative that ALSO converges to the same point on all of them.