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Thread: Have Birds Ever Evolved Into Reptiles?

  1. #1 Have Birds Ever Evolved Into Reptiles? 
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    OK...let's assume that a reptile species was well-suited to a particular niche. Let's further assume that some of these reptiles ventured off into a new niche and then evolved into birds so they could be better adapted to the new niche.

    Question: Have birds ever evolved back into reptiles?

    I have noticed that land mammals have evolved into whales, but not into fishes. They are still mammals. Has any end species evolved back into its ancestor species if and when it switched back to the old niche? (Assuming the niche is available.)


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  3. #2 Re: Have Birds Ever Evolved Into Reptiles? 
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    Quote Originally Posted by williampinn
    OK...let's assume that a reptile species was well-suited to a particular niche. Let's further assume that some of these reptiles ventured off into a new niche and then evolved into birds so they could be better adapted to the new niche.

    Question: Have birds ever evolved back into reptiles?

    I have noticed that land mammals have evolved into whales, but not into fishes. They are still mammals. Has any end species evolved back into its ancestor species if and when it switched back to the old niche? (Assuming the niche is available.)
    The likelihood of it happening is astronomically low. Would not expect it to ever happen on the timescale of billions of years.


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    sometimes an evolutionary step along the way makes it very unlikely that a reversal will ever happen again

    in the case of fish and whales: the gill arch which is an essential part of a fish's breathing apparatus has been used in different parts of the mammal skull going from the jaws to the middle ear

    likewise birds no longer have a front leg that could function in a weight-carrying capacity - whereas many dinosaurs could revert to a quadrupedal stance because in most cases the front legs hadn't shriveled to the point of uselessness, that option no longer appears to exist for birds

    the embryological chasm is just to wide
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    yes, birds evolved into fish. (penguins).
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    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    "Reality is that which, when you stop believing in it, doesn't go away." (Philip K. Dick)
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    Quote Originally Posted by marnixR
    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    So unlikely that it falsifies The Modern Synthesis. Creationists win!
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    Quote Originally Posted by TheBiologista
    Quote Originally Posted by marnixR
    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    So unlikely that it falsifies The Modern Synthesis. Creationists win!
    How do creationists win? Perhaps there is simply a rule like, "You can't unring a bell." In the absense of such a rule, it seems likely that some mammals should have evolved back to reptiles when the dinosaurs became extinct. If the probability is next to zero. Naturally I am curious why that is the case. Aren't you?
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    Quote Originally Posted by spuriousmonkey
    yes, birds evolved into fish. (penguins).
    Oh yes, of course! Thank you! Penguins are definitely fishes, or, in your parlance, fish.
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    Quote Originally Posted by williampinn
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by marnixR
    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    So unlikely that it falsifies The Modern Synthesis. Creationists win!
    How do creationists win? Perhaps there is simply a rule like, "You can't unring a bell." In the absense of such a rule, it seems likely that some mammals should have evolved back to reptiles when the dinosaurs became extinct. If the probability is next to zero. Naturally I am curious why that is the case. Aren't you?
    Precisely what path a given species evolves along has a large degree of chance involved. The mutations that create the variation on which natural selection acts are entirely random. Thus, even at the same starting point in the same environment, two groups of organisms will eventually develop characteristics unique to them. Thus the chances that the paths any group of modern mammals might take would lead EXACTLY back to reptiles, in every detail, is extremely small.

    But we do see descendant groups returning to niches similar to those of their ancestral groups, as with your own example of mammals returning to the marine environment. They have essentially done what you've asked, only the exact physiology to every degree is not the same, but the functionality is nearly so. Selection has shaped similar functions but since the raw material it has to work with is highly variable it didn't get to those functions in the exact same way.
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    Doesn't this question stem from the presumption that birds, at some point, stopped being reptiles? We still classify them as "Reptilia". At what point does something stop being one thing and start being something else?
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    Quote Originally Posted by paralith
    Quote Originally Posted by williampinn
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by marnixR
    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    So unlikely that it falsifies The Modern Synthesis. Creationists win!
    How do creationists win? Perhaps there is simply a rule like, "You can't unring a bell." In the absense of such a rule, it seems likely that some mammals should have evolved back to reptiles when the dinosaurs became extinct. If the probability is next to zero. Naturally I am curious why that is the case. Aren't you?
    Precisely what path a given species evolves along has a large degree of chance involved. The mutations that create the variation on which natural selection acts are entirely random. Thus, even at the same starting point in the same environment, two groups of organisms will eventually develop characteristics unique to them. Thus the chances that the paths any group of modern mammals might take would lead EXACTLY back to reptiles, in every detail, is extremely small.

    But we do see descendant groups returning to niches similar to those of their ancestral groups, as with your own example of mammals returning to the marine environment. They have essentially done what you've asked, only the exact physiology to every degree is not the same, but the functionality is nearly so. Selection has shaped similar functions but since the raw material it has to work with is highly variable it didn't get to those functions in the exact same way.

    Do you think whales will eventually develop gills? Even in an entirely random system of mutations, there is expected value, a kind of determinism that results when you average out hundreds of samples of mutations. A whale with gills would have an advantage and natural selection should skew the the normalizaiton curve of probabilities in favor of gills.
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    Quote Originally Posted by Finger
    Doesn't this question stem from the presumption that birds, at some point, stopped being reptiles? We still classify them as "Reptilia". At what point does something stop being one thing and start being something else?
    Techinically they are both animals, so by that logic evolution does not occur.
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    Quote Originally Posted by williampinn
    Do you think whales will eventually develop gills? Even in an entirely random system of mutations, there is expected value, a kind of determinism that results when you average out hundreds of samples of mutations. A whale with gills would have an advantage and natural selection should skew the the normalizaiton curve of probabilities in favor of gills.
    Certainly, a probability that it won't happen is accompanied by a probability that it will happen. But the additional problem here is that of historic constraint, which spurious knows a lot about. Basically, traits do not exist in isolation. Even if selection is focused on one particular trait, there will be changes in other traits due to the complex ways they relate to each other. Thus you can't just pop a breathing gill in a whale without first changing the structures in the skull and neck, adjusting the circulatory system to route through the gills, etc etc. This represents a stumbling block towards going back to gills, because we don't just need mutations for gills but for all the related structures that make them function with the rest of the body.

    Again, natural selection worked with what it had and instead whales and other marine mammals adapted for holding their breath (using their existing respiratory systems) for a very long time, long enough to feed, mate, or whatever else they need to do under water where there is no air, achieving a functionally similar result to having gills.
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    Quote Originally Posted by paralith
    Basically, traits do not exist in isolation. Even if selection is focused on one particular trait, there will be changes in other traits due to the complex ways they relate to each other. Thus you can't just pop a breathing gill in a whale without first changing the structures in the skull and neck, adjusting the circulatory system to route through the gills, etc etc. This represents a stumbling block towards going back to gills, because we don't just need mutations for gills but for all the related structures that make them function with the rest of the body.
    This sounds so much like the irreducible compexity argument. Somehow the gill will pop into existence and then the other parts won't work right because they must work together. But a partially functional gill could work with the other parts, and those other parts would also mutate gradually as well.

    Quote Originally Posted by paralith
    Again, natural selection worked with what it had and instead whales and other marine mammals adapted for holding their breath (using their existing respiratory systems) for a very long time, long enough to feed, mate, or whatever else they need to do under water where there is no air, achieving a functionally similar result to having gills.
    But evolution always works with more than it has or random mutations would have no value. Something new must be added to the mix or there is no change.
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    Quote Originally Posted by williampinn
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by marnixR
    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    So unlikely that it falsifies The Modern Synthesis. Creationists win!
    How do creationists win?
    Not being serious.

    Quote Originally Posted by williampinn
    Perhaps there is simply a rule like, "You can't unring a bell." In the absense of such a rule, it seems likely that some mammals should have evolved back to reptiles when the dinosaurs became extinct. If the probability is next to zero. Naturally I am curious why that is the case. Aren't you?
    Why the probability is so low? Because of the number of complex changes required to reach a specified outcome via evolution. The probability of species X evolving into a specified species Y is negligibly low, but the probability of X evolving into something, anything, is far better.
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    Quote Originally Posted by TheBiologista

    Why the probability is so low? Because of the number of complex changes required to reach a specified outcome via evolution. The probability of species X evolving into a specified species Y is negligibly low, but the probability of X evolving into something, anything, is far better.
    Actually the reverse is true. It is highly improbable that a species would evolve into just anything. It is very probable that cells will evolve into creatures with two eyes and not one eye or three eyes, etc. It is no accident that most marine animals have gills. Natural selection is the key.

    A bird evolving into an exact clone of its ancestor is improbable, but it should evolve into something similar if the ancestor model is the fittest model. Evolution should work in both directions.

    (Edit): Even with a low probability, given millions of years you would think there would be at least one instance of complete reverse evolution.



    So back to the original question (slightly modified to include some variance)...
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    Quote Originally Posted by williampinn
    Actually the reverse is true. It is highly improbable that a species would evolve into just anything. It is very probable that cells will evolve into creatures with two eyes and not one eye or three eyes, etc. It is no accident that most marine animals have gills. Natural selection is the key.
    Natural selection is key - but natural selection happens after variation is introduced - via mutation. The first step in all of this is random.

    A bird evolving into an exact clone of its ancestor is improbable, but it should evolve into something similar if the ancestor model is the fittest model. Evolution should work in both directions.
    This is, I think, why biologists are such sticklers about the definition of fitness, and why there's been more drama than may be necessary in the other thread you started about fitness. We want to be very specific about what fitness means, but why? Because natural works on the level of individual fitness; if you want to understand why some things have evolved via natural selection and others haven't, you need to think about the very specific meaning and measurement that is fitness, and not other measures like staying power. Thus, why should birds evolve to fill a reptile niche if they're doing just fine in the niche they're in now? Sure, the reptile niche, like that of the crocodile, may be more stable over long periods of evolutionary time, but natural selection is a short-sighted process. As long as individuals are doing very well in their lifetimes at passing along their genes where they are as they are, natural selection will not push them into another niche, even if we humans are cognitively aware that another niche may be better if you want to be a long-lasting species.

    That all being said, I've been trying to point out repeatedly that there ARE cases of descendants moving into niches that may be more typical to reptiles, and have functionally similar traits in order to do well in that niche. It's just that the deep down specifics are not exactly the same. Think of roadrunners - living in the desert, eating insects, running around on the ground - something a lot of lizards do. And these roadrunners do very well there, and perform a lot of the same functions that desert dwelling lizards do. The specifics of the morphology are quite different but natural selection got to the same functions in the quickest and cheapest way possible, by altering what was already there.

    (Edit): Even with a low probability, given millions of years you would think there would be at least one instance of complete reverse evolution.

    So back to the original question (slightly modified to include some variance)...
    Along the lines of what Biologista already said, the likelihood of one organism, in every tiny detail of its morphology, to evolve twice (let's disregard the whole ancestor/descendant thing at this point - evolve twice by any possible path) is extremely low. The likelihood of similar functions evolving in diverse animals that live in similar environments is much higher, and we see it very often.
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    Quote Originally Posted by williampinn
    Quote Originally Posted by TheBiologista

    Why the probability is so low? Because of the number of complex changes required to reach a specified outcome via evolution. The probability of species X evolving into a specified species Y is negligibly low, but the probability of X evolving into something, anything, is far better.
    Actually the reverse is true. It is highly improbable that a species would evolve into just anything. It is very probable that cells will evolve into creatures with two eyes and not one eye or three eyes, etc. It is no accident that most marine animals have gills. Natural selection is the key.
    Obviously by "anything" I meant anything within the constraints of selection and mutation.

    Quote Originally Posted by williampinn
    A bird evolving into an exact clone of its ancestor is improbable, but it should evolve into something similar if the ancestor model is the fittest model. Evolution should work in both directions.
    Evolution does not produce the fittest to an environment in an absolute sense, it produces "fit enough". And you're sorta right, which is why we get convergence.

    Quote Originally Posted by williampinn
    (Edit): Even with a low probability, given millions of years you would think there would be at least one instance of complete reverse evolution.
    Well that depends how many millions of years and how low a probability you're talking about, doesn't it? If the probability is say 1 in 10^12 per year, you would not expect to see the event occur even once within the 4 billion-ish years that life has existed on Earth.
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    Quote Originally Posted by williampinn
    Quote Originally Posted by Finger
    Doesn't this question stem from the presumption that birds, at some point, stopped being reptiles? We still classify them as "Reptilia". At what point does something stop being one thing and start being something else?
    Techinically they are both animals, so by that logic evolution does not occur.
    Not at all what I meant. My point is that it is wrong to think of evolution as "a group of animals turning into another group of animals." It's more accurate to say that one group of animals will diversify and broaden within itself, branching off into several groups within the same set. Each subsequent group then in turn diversifies and branches off into its own set. And so on, and so on.. Its impossible for a lineage to break off into something not connected to its parental set. I also pointed out that birds are already classified as reptiles, so what exactly do you mean when you ask if they could "evolve back into reptiles?" Asking it is like asking "why don't we evolve back into mammals?"
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    Besides the fact that taxonomy is largely arbitrary, birds are generally not considered reptiles. However, both modern reptiles and birds are diapsids.
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    You've got it backwards. Diapsids are a subset of Reptiles, not the other way around. Turtles aren't diapsid, they're anapsid.

    If we still relied on what was generally accepted, then whales would still be fish. Taxonomy may be complex, but it isn't arbitrary. The pattern exists in nature with or without the names we've assigned for our own convenience. No matter what we called them, our concept of a reptile would only exist if we included birds. Here, take a look at the phylogenetic tree for Reptiles and I'll show you what I mean:



    Lets go ahead and move "reptilia" down to exclude dinosaurs and birds. This would make crocodiles the only reptiles in the world. Excluding lizards (subsets of "Lepidosauromorpha") and even turtles (subsets of "Testudines".) I doubt very much that anyone is prepared to declare turtles and lizards non-reptilian (We all saw what happened when they reclassified Pluto.) In order to include even lizards, let alone turtles, we simply must include birds. What's arbitrary is to exclude birds for the sake of tradition.

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    Quote Originally Posted by paralith
    Quote Originally Posted by williampinn
    Actually the reverse is true. It is highly improbable that a species would evolve into just anything. It is very probable that cells will evolve into creatures with two eyes and not one eye or three eyes, etc. It is no accident that most marine animals have gills. Natural selection is the key.
    Natural selection is key - but natural selection happens after variation is introduced - via mutation. The first step in all of this is random.

    A bird evolving into an exact clone of its ancestor is improbable, but it should evolve into something similar if the ancestor model is the fittest model. Evolution should work in both directions.
    This is, I think, why biologists are such sticklers about the definition of fitness, and why there's been more drama than may be necessary in the other thread you started about fitness. We want to be very specific about what fitness means, but why? Because natural works on the level of individual fitness; if you want to understand why some things have evolved via natural selection and others haven't, you need to think about the very specific meaning and measurement that is fitness, and not other measures like staying power. Thus, why should birds evolve to fill a reptile niche if they're doing just fine in the niche they're in now? Sure, the reptile niche, like that of the crocodile, may be more stable over long periods of evolutionary time, but natural selection is a short-sighted process. As long as individuals are doing very well in their lifetimes at passing along their genes where they are as they are, natural selection will not push them into another niche, even if we humans are cognitively aware that another niche may be better if you want to be a long-lasting species.

    That all being said, I've been trying to point out repeatedly that there ARE cases of descendants moving into niches that may be more typical to reptiles, and have functionally similar traits in order to do well in that niche. It's just that the deep down specifics are not exactly the same. Think of roadrunners - living in the desert, eating insects, running around on the ground - something a lot of lizards do. And these roadrunners do very well there, and perform a lot of the same functions that desert dwelling lizards do. The specifics of the morphology are quite different but natural selection got to the same functions in the quickest and cheapest way possible, by altering what was already there.

    (Edit): Even with a low probability, given millions of years you would think there would be at least one instance of complete reverse evolution.

    So back to the original question (slightly modified to include some variance)...
    Along the lines of what Biologista already said, the likelihood of one organism, in every tiny detail of its morphology, to evolve twice (let's disregard the whole ancestor/descendant thing at this point - evolve twice by any possible path) is extremely low. The likelihood of similar functions evolving in diverse animals that live in similar environments is much higher, and we see it very often.
    If you stop and think about it, all your arguments could be made against forward evolution.

    Today I watched a video featuring physicist Michio Kaku who shed some light on why evolution can't go backwards. It has to do with the Big Bang, the expanding universe and entropy. "You can't unbreak an egg." Reverse evolution would be like reverse entropy--it would violate the second law of thermodynamics.
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    Quote Originally Posted by Finger
    Quote Originally Posted by williampinn
    Quote Originally Posted by Finger
    Doesn't this question stem from the presumption that birds, at some point, stopped being reptiles? We still classify them as "Reptilia". At what point does something stop being one thing and start being something else?
    Techinically they are both animals, so by that logic evolution does not occur.
    Not at all what I meant. My point is that it is wrong to think of evolution as "a group of animals turning into another group of animals." It's more accurate to say that one group of animals will diversify and broaden within itself, branching off into several groups within the same set. Each subsequent group then in turn diversifies and branches off into its own set. And so on, and so on.. Its impossible for a lineage to break off into something not connected to its parental set. I also pointed out that birds are already classified as reptiles, so what exactly do you mean when you ask if they could "evolve back into reptiles?" Asking it is like asking "why don't we evolve back into mammals?"
    It is more like saying why don't we devolve into the mammals we were previously. The fact that birds are classified as reptiles only strengthens the notion that they could revert back to reptiles--they already have most of the genetic material they need, so what's the hold up?
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    Quote Originally Posted by i_feel_tiredsleepy
    Besides the fact that taxonomy is largely arbitrary, birds are generally not considered reptiles. However, both modern reptiles and birds are diapsids.
    TThat sounds more accurate. Thank you for clearing that up.
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    Quote Originally Posted by williampinn
    If you stop and think about it, all your arguments could be made against forward evolution.
    not so - the probability of any specific outcome is extremely low, so if you see evolution as having to achieve one particular outcome then your statement would be correct

    however, with "forward" evolution (whatever that may mean) at least one outcome will happen, unless the organism goes extinct
    that's why it's impossible to predict in specific terms which organisms will evolve from certain ancestors - it's a bit like trying to predict who will win the lottery, whereas stating that at least one person WILL win the lottery has a good chance of coming true
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    Quote Originally Posted by marnixR

    not so - the probability of any specific outcome is extremely low,
    What is the probability? In one generation it would be low, but given enough time, a normalization curve kicks in and a specific result is the expected result.

    Quote Originally Posted by marnixR
    that's why it's impossible to predict in specific terms which organisms will evolve from certain ancestors - it's a bit like trying to predict who will win the lottery,
    Not even wrong. If evolution was analogous to the lottery, it wouldn't work. Evolution works because it has two rules the lottery does not have:
    1. Natural selection;
    2. Heredity.

    Both of these rules skew the results in favor of those organisms that are well-adapted to an environment and can pass on their traits to the next generation. It is these two rules that make evolution predictable, otherwise the fossel record would be a hodge podge.
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    Quote Originally Posted by williampinn
    Both of these rules skew the results in favor of those organisms that are well-adapted to an environment and can pass on their traits to the next generation.
    but how can you tell what the environment will be like a hundred years, let alone a million years, from now ?
    after all, if the work of Peter and Rosemary Grant in the Galapagos has shown us anything, it's that the environment and selection pressures can vary wildly even from one year to the next

    the adaptation that works now may be your downfall in the new environment
    that's why all you can predict is that organisms will change over time, but you can't be sure about the specifics of that change
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    Quote Originally Posted by Finger
    You've got it backwards. Diapsids are a subset of Reptiles, not the other way around. Turtles aren't diapsid, they're anapsid.

    If we still relied on what was generally accepted, then whales would still be fish. Taxonomy may be complex, but it isn't arbitrary. The pattern exists in nature with or without the names we've assigned for our own convenience. No matter what we called them, our concept of a reptile would only exist if we included birds. Here, take a look at the phylogenetic tree for Reptiles and I'll show you what I mean:



    Lets go ahead and move "reptilia" down to exclude dinosaurs and birds. This would make crocodiles the only reptiles in the world. Excluding lizards (subsets of "Lepidosauromorpha") and even turtles (subsets of "Testudines".) I doubt very much that anyone is prepared to declare turtles and lizards non-reptilian (We all saw what happened when they reclassified Pluto.) In order to include even lizards, let alone turtles, we simply must include birds. What's arbitrary is to exclude birds for the sake of tradition.

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    Since mammals also evolved from reptiles, why not call them reptiles as well?
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    Quote Originally Posted by marnixR
    but how can you tell what the environment will be like a hundred years, let alone a million years, from now ?
    LOL! Climate models? How can we tell that spring will follow winter? The rules might change. But natural selection can't work if they do too frequently.

    Quote Originally Posted by marnixR
    after all, if the work of Peter and Rosemary Grant in the Galapagos has shown us anything, it's that the environment and selection pressures can vary wildly even from one year to the next

    the adaptation that works now may be your downfall in the new environment
    that's why all you can predict is that organisms will change over time, but you can't be sure about the specifics of that change
    Point taken but it is irrelevant, since my question extrapolates history and not the future. Even if we extrapolated into the future, we could make a specific prediction and eventually be right if there is enough time.
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    william, as marnix, biologista and others have been trying to point out, one of the main issues here is predictability. Spring may follow winter but if we have another ice age spring and summer may be all of two months long and the rest is winter and fall and you have drastically changed the conditions with which animals have to deal with. We don't know what mutations will pop up, so though we may be able to have a rough prediction of the types of functions animals may need in certain environments we can't be sure what solutions they will find. But we most certainly know they will find A solution, we just don't know which one.

    This is not an argument or evidence against evolution and if you continue to stubbornly insist that it is you'll find your threads locked.
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    Quote Originally Posted by Finger
    You've got it backwards. Diapsids are a subset of Reptiles, not the other way around. Turtles aren't diapsid, they're anapsid.

    If we still relied on what was generally accepted, then whales would still be fish. Taxonomy may be complex, but it isn't arbitrary. The pattern exists in nature with or without the names we've assigned for our own convenience. No matter what we called them, our concept of a reptile would only exist if we included birds. Here, take a look at the phylogenetic tree for Reptiles and I'll show you what I mean:



    Lets go ahead and move "reptilia" down to exclude dinosaurs and birds. This would make crocodiles the only reptiles in the world. Excluding lizards (subsets of "Lepidosauromorpha") and even turtles (subsets of "Testudines".) I doubt very much that anyone is prepared to declare turtles and lizards non-reptilian (We all saw what happened when they reclassified Pluto.) In order to include even lizards, let alone turtles, we simply must include birds. What's arbitrary is to exclude birds for the sake of tradition.

    Source
    "Mammals are a clade, and therefore the cladists are happy to acknowledge the traditional taxon Mammalia; and birds, too, are a clade, universally ascribed to the formal taxon Aves. Mammalia and Aves are, in fact, subclades within the grand clade of the Amniota. But the traditional class reptilia is not a clade. It is just a section of the clade Amniota: the section that is left after the Mammalia and Aves have been hived off. It cannot be defined by synapomorphies, as is the proper way. It is instead defined by a combination of the features it has and the features it lacks: reptiles are the amniotes that lack fur or feathers. At best, the cladists suggest, we could say that the traditional Reptila are 'non-avian, non-mammalian amniotes"

    This quote from Colin Tudge expresses it much better than I ever could. If we are to attempt to avoid creating arbitrary taxonomies we must decide that both birds and mammals are both reptiles, which would completely overturn the traditional use of the word.
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    Sorry about getting off-topic. I'd understand if the mods wanted to break this off into a new thread.
    Quote Originally Posted by i_feel_tiredsleepy
    "Mammals are a clade, and therefore the cladists are happy to acknowledge the traditional taxon Mammalia; and birds, too, are a clade, universally ascribed to the formal taxon Aves. Mammalia and Aves are, in fact, subclades within the grand clade of the Amniota. But the traditional class reptilia is not a clade. It is just a section of the clade Amniota: the section that is left after the Mammalia and Aves have been hived off. It cannot be defined by synapomorphies, as is the proper way. It is instead defined by a combination of the features it has and the features it lacks: reptiles are the amniotes that lack fur or feathers. At best, the cladists suggest, we could say that the traditional Reptila are 'non-avian, non-mammalian amniotes"

    This quote from Colin Tudge expresses it much better than I ever could. If we are to attempt to avoid creating arbitrary taxonomies we must decide that both birds and mammals are both reptiles, which would completely overturn the traditional use of the word.
    But, don't you find "except the ones with hair or feathers" a bit arbitrary itself? What's the justification for that exception anyway? And it would still exclude more than just aves and mammals, but any other dinosaur with feathers or therapsid with hair. I'm sorry, but it just doesn't make much sense to me. Its like old classifications that used to list Humans as "apes, but not really."

    Or are you saying that "Reptile" isn't a word that would be used in scientific classification anymore?
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    Quote Originally Posted by Finger
    But, don't you find "except the ones with hair or feathers" a bit arbitrary itself? What's the justification for that exception anyway? And it would still exclude more than just aves and mammals, but any other dinosaur with feathers or therapsid with hair. I'm sorry, but it just doesn't make much sense to me. Its like old classifications that used to list Humans as "apes, but not really."

    Or are you saying that "Reptile" isn't a word that would be used in scientific classification anymore?
    Essentially the way we use reptile in the popular sense isn't valid from a cladistic sense. It isn't possible to classify the traditionally defined reptiles separate from mammals and birds without arbitrary conditions like the presence of hair or feathers and warm-blood. All mammals can be classified together, as can all birds with each other. However, all reptiles would have to include both mammals and birds not just the traditionally defined reptiles.
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    The environment is both diverse and changing, as are lifeforms who are diverse and changing and change in function of both changing environment and other changing lifeforms(since the lifeforms themselves are part of the dynamic environment).

    reptiles evolved from a specific matrix of features and in various specific environments, what was advantageous for reptile evolution may not be required for birds who may already possess adaptations that offer the same functionality. So its unlikely you would get a reptile from a bird, but its possible you might get some animal that is reptile-like in some ways millions of years from now.

    Bacteria is still around today and will continue to be around, we cant detect microscopic molecules of food, nor can we live on tiny molecules, cant live in cracks kilometers below the surface, nor inside the bowels of another human being, these are environments for which we are not adapted, that why different types of organism can coexist.

    Survival of the fittest is just an expression, a simplification. Its not about "fittest" in any absolute term, and its not even about the best adapted either because when a catastrophic change occurs the "fittest" can be wiped out and replaced by an unfit that happens to cope with the new environment or to live in an environment that is affected in a different way.

    One tribe of baboons, the alpha and most agressive/assertive members that are more likely to survive in a certain set of situations, got completely wiped out because they were the ones who ate meat infected with a deadly disease.
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    [quote="williampinn"]
    Quote Originally Posted by paralith
    william, as marnix, biologista and others have been trying to point out, one of the main issues here is predictability. Spring may follow winter but if we have another ice age spring and summer may be all of two months long and the rest is winter and fall and you have drastically changed the conditions with which animals have to deal with. We don't know what mutations will pop up, so though we may be able to have a rough prediction of the types of functions animals may need in certain environments we can't be sure what solutions they will find. But we most certainly know they will find A solution, we just don't know which one.

    This is not an argument or evidence against evolution and if you continue to stubbornly insist that it is you'll find your threads locked.
    I am not aware that I am stubbornly insisting anything. I am simply politely pointing out that you can in fact make predictions. Assume that the future environments are random. Whether you predict an ice age or an interglacial, given enough time, you will eventually be right. Try a probability experiment. Program your computer to spit out random integers within a certain range. Predict that the number 7 will eventually appear. It will eventually appear.

    Here is the math:
    If your range is between zero and 1 X 10^6, the probability of NOT getting 7 after one try is .999999. Seems pretty hopeless. So the question is, within how many tries will get you 7? The formula is:

    ln .999999^X = ln .0000001

    The answer is approximately 16,000,000 tries. The probability is very close to one or .999999887. The fact is anything that is remotely probable will happen eventually given a sufficient time frame.
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    [quote="williampinn"]
    Quote Originally Posted by williampinn
    Quote Originally Posted by paralith
    william, as marnix, biologista and others have been trying to point out, one of the main issues here is predictability. Spring may follow winter but if we have another ice age spring and summer may be all of two months long and the rest is winter and fall and you have drastically changed the conditions with which animals have to deal with. We don't know what mutations will pop up, so though we may be able to have a rough prediction of the types of functions animals may need in certain environments we can't be sure what solutions they will find. But we most certainly know they will find A solution, we just don't know which one.

    This is not an argument or evidence against evolution and if you continue to stubbornly insist that it is you'll find your threads locked.
    I am not aware that I am stubbornly insisting anything. I am simply politely pointing out that you can in fact make predictions. Assume that the future environments are random. Whether you predict an ice age or an interglacial, given enough time, you will eventually be right. Try a probability experiment. Program your computer to spit out random integers within a certain range. Predict that the number 7 will eventually appear. It will eventually appear.

    Here is the math:
    If your range is between zero and 1 X 10^6, the probability of NOT getting 7 after one try is .999999. Seems pretty hopeless. So the question is, within how many tries will get you 7? The formula is:

    ln .999999^X = ln .0000001

    The answer is approximately 16,000,000 tries. The probability is very close to one or .999999887. The fact is anything that is remotely probable will happen eventually given a sufficient time frame.
    william, no one is arguing that there isn't a possibility. I've said as much several times. It's just very unlikely and given that the probability is so low of arriving at the EXACT same morphological form twice, no, a couple million or even a couple billion years is not long enough to make that probability a statistical inevitability. And that's why it's no surprise nor any mark against evolution that it hasn't happened yet.
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    Quote Originally Posted by icewendigo
    reptiles evolved from a specific matrix of features and in various specific environments, what was advantageous for reptile evolution may not be required for birds who may already possess adaptations that offer the same functionality. So its unlikely you would get a reptile from a bird, but its possible you might get some animal that is reptile-like in some ways millions of years from now.
    Interesting. It certainly makes sense that if a bird has the same functionality as a reptile, it would not need to become a reptile. But then why did reptiles evolve into birds and not terradactyl-like species? Assuming reptiles and birds have similar functionality, shouldn't birds look more like flying lizards?


    Quote Originally Posted by icewendigo
    Survival of the fittest is just an expression, a simplification. Its not about "fittest" in any absolute term, and its not even about the best adapted either because when a catastrophic change occurs the "fittest" can be wiped out and replaced by an unfit that happens to cope with the new environment or to live in an environment that is affected in a different way.

    One tribe of baboons, the alpha and most agressive/assertive members that are more likely to survive in a certain set of situations, got completely wiped out because they were the ones who ate meat infected with a deadly disease.
    I see your point, but I think fittest means that if the environment changes, only those species that were smart enough, fast enough, strong enough or just plain lucky enough will survive the next food poisoning or asteroid impact. It can also mean that if the environment stays constant, those who are fittest will maintain their status as such.
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    [quote="paralith"]
    Quote Originally Posted by williampinn
    Quote Originally Posted by williampinn
    Quote Originally Posted by paralith
    william, as marnix, biologista and others have been trying to point out, one of the main issues here is predictability. Spring may follow winter but if we have another ice age spring and summer may be all of two months long and the rest is winter and fall and you have drastically changed the conditions with which animals have to deal with. We don't know what mutations will pop up, so though we may be able to have a rough prediction of the types of functions animals may need in certain environments we can't be sure what solutions they will find. But we most certainly know they will find A solution, we just don't know which one.

    This is not an argument or evidence against evolution and if you continue to stubbornly insist that it is you'll find your threads locked.
    I am not aware that I am stubbornly insisting anything. I am simply politely pointing out that you can in fact make predictions. Assume that the future environments are random. Whether you predict an ice age or an interglacial, given enough time, you will eventually be right. Try a probability experiment. Program your computer to spit out random integers within a certain range. Predict that the number 7 will eventually appear. It will eventually appear.

    Here is the math:
    If your range is between zero and 1 X 10^6, the probability of NOT getting 7 after one try is .999999. Seems pretty hopeless. So the question is, within how many tries will get you 7? The formula is:

    ln .999999^X = ln .0000001

    The answer is approximately 16,000,000 tries. The probability is very close to one or .999999887. The fact is anything that is remotely probable will happen eventually given a sufficient time frame.
    william, no one is arguing that there isn't a possibility. I've said as much several times. It's just very unlikely and given that the probability is so low of arriving at the EXACT same morphological form twice, no, a couple million or even a couple billion years is not long enough to make that probability a statistical inevitability. And that's why it's no surprise nor any mark against evolution that it hasn't happened yet.
    One problem: you are forgetting that natural selection and heredity raise the probability substantially (see Blind Watchmaker by Richard Dawkins). My experiment was completely random and yet the probability was found to be close to one--the highest possible value for probability.

    Now you seem pretty certain that nothwithstanding a great deal of time, a bird can not elvolve back to a reptile. Show us your numbers and let's crunch them.
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    Interesting. It certainly makes sense that if a bird has the same functionality as a reptile, it would not need to become a reptile. But then why did reptiles evolve into birds and not terradactyl-like species? Assuming reptiles and birds have similar functionality, shouldn't birds look more like flying lizards?
    All of us are mutants, maybe this would help to consider. We all undergo a crazy amount of genetic damage that is being repaired on a continual basis but not all repairs get it right. Often a mutation has Zero effect that can be observed in a given environment or situation. There are people who have an alternate form of T-cell molecules, which has no apparent effect, except if they contract the hiv virus in which case they dont develop aids symptoms. The reptileish birds may have lived with the more birdish birds, but the repilish birds got wiped out for any number of reasons(disease, mating, reproduction, thermal, digestion,etc) and the more bird like survived, if birds were different then what they are now you would wonder why they are like that.

    The ability(or rather the condition) to have diversified progeny in which occasional individuals are relatively unfit(for the current environment) and die is a relative advantage, because if the environment changes it may be the type of ones that previously were less adapted that now find themselves adapted.

    "or just plain lucky enough"
    luck(randomness/unpredictability) is a factor but theres no luckyness trait, thats why the more diversified and spreadout life becomes the more it survives (at some point I think all life on earth was wiped out except for bacterias deep beneath the earth, if that is so we are alive because life had diversified and spread not because we were an animal/bacteria with any kind of being fitter than others at the surface.

    (We are also the result of cooperation/symbiosis too)
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    Natural selection can actually reduce the probability if, as I have tried to describe before, there are historical constraints. That makes the cost of certain changes increase substantially because you can't change just one trait but you have to change many altogether. When there's a lower cost way of achieving the same output, that is what natural selection will favor. In fact I think it would be more likely given a completely random wandering of traits due to a release in the selective pressure.

    The thing about irreducible complexity arguments is that they're saying arriving at complex function at all is impossible. Natural selection definitely improves the odds of this better than random wandering because it maintains functionality. What you're talking about isn't just anything that falls in the realm of complex function, but a very specific form that has already evolved once before. That's a different story.
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    Quote Originally Posted by icewendigo

    All of us are mutants, maybe this would help to consider. We all undergo a crazy amount of genetic damage that is being repaired on a continual basis but not all repairs get it right. Often a mutation has Zero effect that can be observed in a given environment or situation. There are people who have an alternate form of T-cell molecules, which has no apparent effect, except if they contract the hiv virus in which case they dont develop aids symptoms. The reptileish birds may have lived with the more birdish birds, but the repilish birds got wiped out for any number of reasons(disease, mating, reproduction, thermal, digestion,etc) and the more bird like survived, if birds were different then what they are now you would wonder why they are like that.
    If you made the claim that a flying lizard evolved from a ground lizard, I would immediately see the connection. If I hadn't read that birds evolved from reptiles, I never would have guessed. From what I understand, you can find within the bird's DNA something that points to its reptilian ancestry. It already has the the genes? So it seems the bird species would not even need a random mutation to revert back to a lizard. Our species, for example, could become apes again if just a couple of chromosomes that are fused together became separated. It is a wonder to me why reverse elvolution isn't as common as back and forth.
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    Quote Originally Posted by williampinn
    If you made the claim that a flying lizard evolved from a ground lizard, I would immediately see the connection. If I hadn't read that birds evolved from reptiles, I never would have guessed. From what I understand, you can find within the bird's DNA something that points to its reptile ancestry. It already has the the genes, so it seems the bird species would not even need a random mutation to revert back to a lizard. Our species, for example, could become apes again if just a couple of chromosomes that are fused together became seperated. It is a wonder to me why reverse elvolution isn't as common as back and forth.
    Genetic analyses of relatedness look at sequence identity - how many of the actual nucleotides in the sequence are the same? This means that even if there are similar genes or sequence units in birds and reptiles, the sequences of those genes are not exactly the same, the proteins they generate are not all the same. Even more importantly, the regulatory sequences that determine what and how much of a protein gets made and when, could be radically different even if the proteins themselves are the same. A difference in just a few nucleotides can radically affect the functional result. Even if the majority of the sequences are similar, the differences can be profound when it comes to phenotype.

    Reverse evolution isn't very common for the same reason that two identical populations that are merely separated geographically (but have the same type of environment) can still become very different, as I already explained. Mutation is random. The likelihood of the same mutations happening in two distinct populations is low. The likelihood of a mutation occurring in exactly the same spot that returns it to the ancestral conditions is low. But it is a possibility, and many algorithms that calculate relatedness based on sequence difference take the rate at which this happens into account. It's certainly more common in sequences not under selective pressure.
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    Quote Originally Posted by paralith
    Natural selection can actually reduce the probability if, as I have tried to describe before, there are historical constraints. That makes the cost of certain changes increase substantially because you can't change just one trait but you have to change many altogether. When there's a lower cost way of achieving the same output, that is what natural selection will favor. In fact I think it would be more likely given a completely random wandering of traits due to a release in the selective pressure.

    The thing about irreducible complexity arguments is that they're saying arriving at complex function at all is impossible. Natural selection definitely improves the odds of this better than random wandering because it maintains functionality. What you're talking about isn't just anything that falls in the realm of complex function, but a very specific form that has already evolved once before. That's a different story.
    OK, if the bird took the most economic pathway, I would estimate it would evolve to a reptile; it already has the traits. To make an analogy: Suppose you had an economy car and you made several changes to its charactoristics because you wanted a different color, style, more horsepower, etc. Then later you changed your mind because gas prices were rising and you decided you need an economy car again. Would it be easier just to undo the changes you've made or would it be easier to build a whole new car?

    I think it would be more economical if you simply undid the traits you added on top of the original car. If a whale never becomes a fish, then maybe it was never a fish to begin with, so it is not stuck with a fish blueprint and is free to evolve into something else.
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    Quote Originally Posted by paralith

    Reverse evolution isn't very common for the same reason that two identical populations that are merely separated geographically (but have the same type of environment) can still become very different, as I already explained. Mutation is random. The likelihood of the same mutations happening in two distinct populations is low. The likelihood of a mutation occurring in exactly the same spot that returns it to the ancestral conditions is low. But it is a possibility, and many algorithms that calculate relatedness based on sequence difference take the rate at which this happens into account. It's certainly more common in sequences not under selective pressure.
    That is surprising when you consider that there are many separated species, even with different common ancestors that have similar end species with similar traits. Natural selection is very powerful according to Dawkins. He gave some examples in his book "The Blind Watchmaker."

    A lot of people assume that anything random will somehow get in the way of an expected end result. If there are more degrees of freedom, the expected result is more likely, not less likely to occur than within a deterministic system where only birds can decend from birds.
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    Quote Originally Posted by williampinn
    Quote Originally Posted by paralith
    Quote Originally Posted by williampinn
    Quote Originally Posted by TheBiologista
    Quote Originally Posted by marnixR
    which is patent nonsense when even a 7-year old knows that a penguin is a chocolate bar
    So unlikely that it falsifies The Modern Synthesis. Creationists win!
    How do creationists win? Perhaps there is simply a rule like, "You can't unring a bell." In the absense of such a rule, it seems likely that some mammals should have evolved back to reptiles when the dinosaurs became extinct. If the probability is next to zero. Naturally I am curious why that is the case. Aren't you?
    Precisely what path a given species evolves along has a large degree of chance involved. The mutations that create the variation on which natural selection acts are entirely random. Thus, even at the same starting point in the same environment, two groups of organisms will eventually develop characteristics unique to them. Thus the chances that the paths any group of modern mammals might take would lead EXACTLY back to reptiles, in every detail, is extremely small.

    But we do see descendant groups returning to niches similar to those of their ancestral groups, as with your own example of mammals returning to the marine environment. They have essentially done what you've asked, only the exact physiology to every degree is not the same, but the functionality is nearly so. Selection has shaped similar functions but since the raw material it has to work with is highly variable it didn't get to those functions in the exact same way.

    Do you think whales will eventually develop gills? Even in an entirely random system of mutations, there is expected value, a kind of determinism that results when you average out hundreds of samples of mutations. A whale with gills would have an advantage and natural selection should skew the the normalizaiton curve of probabilities in favor of gills.
    lol.

    you don't even realize that gills evolved after lungs.
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