Why Gradualism?

In Why Evolution is True, Jerry Coyne writes that gradualism is one of the six tenets of “the modern theory of evolution” (which he equates with Darwinism – see page 3).

Eugene Koonin writes that the tenet of gradualism is known to be false (The Logic of Chance p. 398).

Yet gradualism is obviously still quite popular here in “The Skeptical Zone.”

Surely gradualism is not a logical requirement or entailment of the theory of evolution. Neither is it supported by the evidence.

So given what we know about evolution, why do evolutionists still cling to gradualism? My suspicion is that the alternative smacks too much of miracles. So gradualism is more of a religious conviction than a scientific one.

What is the evidence for and against the gradualist hypothesis?

195 thoughts on “Why Gradualism?

  1. There is no conflict between punctuated equilibrium and gradualism other than in the minds of people who appear not to understand one or both.

  2. Allan Miller:
    phoodoo,

    You’d already decided to be an ass in your very first post to me, to which that was a response, so fuck off.

    Oh really? Hm, what was your first post back on your return, let’s see if I can recall?

    Allan Miller:
    Rumraket,

    Hahaha! Phoodoo on phitness! Plus ça change …

    Manger de la merde, Alain!

  3. Allan Miller: You took exception to that?

    Double standards are the standard for them. It’s a problem for them that a complete record of the evolution of the eye, step by step, molecule by molecule, is not available but not a problem to them to claim the same eye was Intelligently Designed on the basis of nothing at all.

    It’s hypocrisy wrapped in the Dunning–Kruger effect.

  4. OMagain: It’s a problem for them that a complete record of the evolution of the eye, step by step, molecule by molecule, is not available

    Which eye? Didn’t it evolve like 18 times at least?

    Did it happen in the same order each time? Or did the pupil come first sometimes, and other times the light sensitive spot came first? Is the tear duct usually last?

  5. OMagain,

    Those light sensitive spots, with little indentation mutations must be ubiquitous as heck. I wonder if that is an eye starting in the back of my knees? That could be handy.

  6. phoodoo,

    Which eye? Didn’t it evolve like 18 times at least?

    Which flagellum was Intelligently Designed?

    Did it happen in the same order each time? Or did the pupil come first sometimes, and other times the light sensitive spot came first? Is the tear duct usually last?

    The eye did not evolve according to you. So what purpose would there be in even attempting to have that discussion with you?

    Those light sensitive spots, with little indentation mutations must be ubiquitous as heck. I wonder if that is an eye starting in the back of my knees? That could be handy.

    We all await the true version of events. You know where the thread is.

  7. vjtorley,

    But if you don’t like the design of the human eye, then I’m going to pose Huxley’s question to you: “What is your alternative?”

    Why don’t animals need glasses?

  8. vjtorley,

    But if you don’t like the design of the human eye, then I’m going to pose Huxley’s question to you: “What is your alternative?”

    Are you going to simply ignore the fact then that you’ve no Intelligent Design based explanation for the origin of eyes? Presumably you will continue to believe they were indeed Intelligently Designed, but why?

  9. vjtorley,
    If you honestly believe that eyes were designed then how do you explain the fact that something like 65% of people need glasses to adjust their vision? Could your designer not have made eyes that regrow, like teeth? Or eyes that adjusted themselves over time?

    I mean, you’ve already linked to articles about how clever the design of eyes are, could your designer not have gone a little further and actually make them work properly for life?

    It’s almost as if eyes start to fail late in life, after reproduction ability ends. Does your designer have something against old people?

  10. Allan Miller: There is no conflict between punctuated equilibrium and gradualism other than in the minds of people who appear not to understand one or both.

    Perhaps I might convince you to change your mind on that.

    Unless you count Gould among those unfortunates who don’t understand either gradualism or punctuated equilibrium.

    …punctuated equilibrium refutes the third and most general meaning of Darwinian gradualism…

    – Stephen Jay Gould. The Structure of Evolutionary Theory. p. 756

    Refutes is a pretty strong word.

  11. phoodoo: Those light sensitive spots, with little indentation mutations must be ubiquitous as heck.

    What with eyes being so obviously adaptive and easy to evolve it’s a miracle we even have light-sensitive spots at all any more. Though even if we didn’t have them any more evolutionists would still have to make them up.

  12. OMagain: If you honestly believe that eyes were designed then how do you explain the fact that something like 65% of people need glasses to adjust their vision?

    Original sin;-) Perhaps when ‘death’ entered the world, so did myopia.

  13. OMagain: It’s almost as if eyes start to fail late in life, after reproduction ability ends.

    Praise god, from whom all hydrophilic polymers flow.

  14. Mung,

    Gould is wrong. I have a suspicion that his Marxism got the better of him here. He was looking for a theory of revolutions, and a revolutionary theory. He over-inflates the case on both. I also think you exhibit a confirmation bias in failing to give any weight to the fact that he only ‘refutes’ the third of the possible senses of gradualism. What of one and two?

    Since we are holding up glove-puppets, I invite you to shadow box with Richard Dawkins, in his chapter ‘Puncturing Punctuationism’ in The Blind Watchmaker***

    *** I am inclined to report serendipitious typos. On this occasion, I nearly posted this with “The Bling Watchmaker“!

  15. To put it another way, gradualism and punctuated equilibrium are only in conflict under a rather particular definition of gradualism designed to make them so. If we were to examine the entire historic genomic succession from a common ancestor to a later pair, one of which exhibited morphological stasis and the other appeared suddenly in the fossil record, would we see a discontinuity anywhere in the succession?

    If not, I don’t see how gradualism would be refuted by such patterns, except in the sense of ‘gradual means no geologically rapid change … and no stasis either for that matter’. Eldredge and Gould’s mechanism would not, on the face of it, lead to any such discontinuity. It’s not a genetic mechanism at all.

  16. Mung: Allan Miller: There is no conflict between punctuated equilibrium and gradualism other than in the minds of people who appear not to understand one or both.

    Perhaps I might convince you to change your mind on that.

    Unless you count Gould among those unfortunates who don’t understand either gradualism or punctuated equilibrium.

    …punctuated equilibrium refutes the third and most general meaning of Darwinian gradualism…

    – Stephen Jay Gould. The Structure of Evolutionary Theory. p. 756

    Refutes is a pretty strong word.

    Haha.

    The problem is Gould doesn’t understand punctuated equilibrium!

    Perhaps Allan is on to something!

  17. phoodoo,

    Haha.

    The problem is Gould doesn’t understand punctuated equilibrium!

    Perhaps Allan is on to something!

    So you tell me why I should agree with Gould (with whom you would disagree on every single evolution-related issue) rather than Dawkins (with whom you would disagree on every single evolution-related issue)? Your disagreements with them would include the existence of both PE and of gradualism …

    Perhaps also explain why PE is not at odds with Gould’s first 2 senses of gradualism, and what they actually are, but only Gould’s personal definition 3 – and explain what that is.

    This is typical of the average Creationist trying to claim support from evolutionists, in argument by quote. Their pet authority could not possibly be wrong (On This Alone), even if the person rooting for them does not themselves understand the issue, and thinks everything else the authority says is tosh. ‘Tis enough that the authority disagrees with their present interlocutor. Another authority says otherwise … then what?

    Stadtler and Waldorf strike again.

    Hahaha.

  18. Here’s the question for those ostensibly supporting Gould and the ‘refutation’ of gradualism.

    In what way do the changes involved in PE, and their manner of distribution in populations, differ from the changes involved in ‘gradualism’?

    Here’s another: is it a matter of size or rate?

  19. Allan Miller,

    In what way do the changes involved in PE, and their manner of distribution in populations, differ from the changes involved in ‘gradualism’?

    Welcome back 🙂
    How do you think gradualism supports the evolution of complex systems such as the circulatory system, where all the components depend on each other?

  20. A few questions:

    Is Gould’s PE based on fossil data or on genomic data?

    If you look at molecular evolution, is there any evidence for PE?

    Is there any evidence at all for variable rates of molecular evolution corresponding to punctuation events?

  21. colewd,

    Welcome back

    Thanks!

    How do you think gradualism supports the evolution of complex systems such as the circulatory system, where all the components depend on each other?

    It doesn’t, especially – if placing it in opposition to saltation or PE, none of them refers particularly to a given system, and none of them would be more palatable to your dyed-in-the-wool Creationist sympathies. Although we can see in the development of an individual from a zygote (forget mammals for now), these components do not depend on each other in quite the way you seem to imagine. Irreducible complexity is not reliably demonstrated by the removal of an individual’s heart.

  22. colewd:
    Allan Miller,

    Welcome back
    How do you think gradualism supports the evolution of complex systems such as the circulatory system, where all the components depend on each other?

    Gradualism doesn’t support anything. I think you may mean the converse, asking how the evolution of complex systems supports, or, more correctly, is consistent with gradualism. Do you have an opinion on that? One would also need to know which definition of gradualism you are inquiring about.

    If we interpret it as merely a contrast with saltationism, then of course complex systems imply gradualism. Complicated systems of mutually dependent parts are unlikely to arise in one step. Gradual co-evolution of the parts makes much more sense.

    Now you may intend the claim that only complete systems are useful and that partial systems can have no advantages. In other words, “What good is half an eye?” or “What good is half a wing?”. The answer to that is, in the first case, to show living species with “half an eye”, and, in both cases to present plausible uses for intermediate stages.

  23. petrushka:
    A few questions:

    Is Gould’s PE based on fossil data or on genomic data?

    If you look at molecular evolution, is there any evidence for PE?

    Is there any evidence at all for variable rates of molecular evolution corresponding to punctuation events?

    Who were these questions for? The answers are “fossil”, “possibly, depending on how you interpret the data”, and “possibly, depending on how you interpret the data”.

    There is some evidence that rates of molecular evolution are correlated with rates of speciation. Does that support PE? There is good evidence that rates of molecular evolution are highly variable. There is some evidence that rates of molecular and morphological evolution can sometimes be correlated within lineages or across clades. Does that support PE? There is no way that I can see to determine whether fast molecular evolution corresponds to punctuation events unless you can observe a punctuation event and assay molecular evolutionary rates in real time. Conceivably one might do that using ancient DNA, but good luck gathering the data.

    Me, I’d look for evidence elsewhere. Does the proposed mechanism of PE actually function? Does speciation typically occur in peripheral isolates? Probably not.

  24. petrushka,

    Is Gould’s PE based on fossil data or on genomic data?

    Fossil

    If you look at molecular evolution, is there any evidence for PE?

    Not directly – that was the point of my question above. Eldredge and Gould’s mechanism (originally allopatric speciation, then something else I’d have to look up) would not generally leave a signal in genomes. Evidence is mostly based on morphology, which is likely biased towards a view consisting mainly of non-neutral alleles. Neutral evolution sails on regardless.

    Is there any evidence at all for variable rates of molecular evolution corresponding to punctuation events?

    I’m not aware of any.

  25. There is an element of ‘selection-or-drift?’ in the ‘PE-or-gradual?’ question (if we accept, for no particular reason, Gould’s Definition 3, which I feel was engineered specifically to make PE at odds with it).

    It is unlikely that there was never a speciation event*** associated with stasis followed by rapid change. It is also unlikely that there was never a speciation event involving ‘phyletic gradualism’. Or a bit ‘o’ both. Also unlikely that morphological stasis between nodes was associated with cessation of all change.

    *** That reminds me: that’s what PE is about – in PE, change is said to mostly occur around speciation events, and anagenesis (change in lineage) is limited.

  26. Allan Miller: So you tell me why I should agree with Gould…

    You can disagree with Gould. But using Gould to contradict those dangerous Creationists does come with a built in problem, as I pointed out.

    Allan Miller: There is no conflict between punctuated equilibrium and gradualism other than in the minds of people who appear not to understand one or both.

    Stephen Jay Gould comes to mind. 🙂

  27. Allan Miller,

    . Although we can see in the development of an individual from a zygote (forget mammals for now), these components do not depend on each other in quite the way you seem to imagine. Irreducible complexity is not reliably demonstrated by the removal of an individual’s heart.

    In this Zygote the pre existence of the information (DNA) already exists to build the complete system and the Zygote has access to oxygen through the mother until development is finished. Oxygen transport is mission critical to multicellularity and it is a interdependent complex system.

  28. colewd: In this Zygote the pre existence of the information (DNA) already exists to build the complete system and the Zygote has access to oxygen through the mother until development is finished. Oxygen transport is mission critical to multicellularity and it is a interdependent complex system.

    There’s your ignorance of biology talking again. Size and metabolic rate are both important in deciding how elaborate oxygen transport has to be. There are land-living vertebrates without lungs that get all the oxygen they need through their skin. There are little worms and many larger animals that have no special system for oxygen transport at all. There are animals in which the blood has no oxygen-transport function.

    And your first sentence is a change of subject from a system to the genetic “information” used to build that system. The point was about gradual construction of a system, which you always hint but never quite manage to say doesn’t happen. Perhaps if you made some actual claims rather than winking and nudging, your points would be clearer.

  29. John Harshman,

    There’s your ignorance of biology talking again. Size and metabolic rate are both important in deciding how elaborate oxygen transport has to be. There are land-living vertebrates without lungs that get all the oxygen they need through their skin. There are little worms and many larger animals that have no special system for oxygen transport at all. There are animals in which the blood has no oxygen-transport function.

    How does this explain the evolution of a completely different strategy of providing cellular oxygen with interdependent parts?

    And your first sentence is a change of subject from a system to the genetic “information” used to build that system. The point was about gradual construction of a system, which you always hint but never quite manage to say doesn’t happen. Perhaps if you made some actual claims rather than winking and nudging, your points would be clearer.

    This is all the same subject which is how does a complex system evolve incrementally. There is no complete explanation until the origin of the genetic information to build that system is explained. Allan brought the genetic information part of the discussion in when he surfaced the Zygote analogy.

  30. colewd: In this Zygote the pre existence of the information (DNA) already exists to build the complete system

    So what? It’s still a gradual process building IC from scratch. It’s game over, no matter how much you try to move the goalposts. IC systems can be build gradually given the right conditions, despite the interdependence of the system’s parts.
    Your stupid handwaving ignores the obvious fact that all the evolutionary precursors of current IC systems would also be DNA based organisms.

    Heh

    colewd: the Zygote has access to oxygen through the mother until development is finished

    Oh yeah? What about avian eggs?
    And so fucking what anyway?

  31. John Harshman: Who were these questions for?

    Some questions are just questions. I always assumed that speciation was not triggered by accelerated rates of molecular evolution. Or more specifically, accelerated rates of mutation.

    Just curiosity.

  32. dazz,

    colewd: the Zygote has access to oxygen through the mother until development is finished

    Oh yeah? What about avian eggs?

    From Scientific American:

    When oxygen enters an animal’s lungs, it is shuttled and distributed by the bloodstream. It is also the bloodstream that carries carbon dioxide back to the lungs to be breathed out. Animals that grow inside their mothers, like humans, get their oxygen from their directly mothers. The blood stream of the baby animal and the mother are connected via an umbilical cord, which allows the baby to collect oxygen that his or her mother breathes in as well as use the mother’s lungs to expel the carbon dioxide.
    How do animals, such as chickens, which develop inside an egg outside of their mothers’ bodies and therefore do not have umbilical cords, take in oxygen and get rid of carbon dioxide? Bird and reptile eggs have a hard shell. Directly under the shell are two membranes. Between the membranes is a small air cell, also called an air sack, filled with oxygen. As the animal develops it uses the oxygen, which must be replenished, and it also has to release carbon dioxide. How does this happen? Well, if you examine a chicken egg carefully with a magnifying glass, you’ll see that there are tiny little holes, called pores, in the shell. In this activity, we’ll see how those work to let the developing chick breathe.

    And so fucking what anyway?

    If you continue to make bold assertions, it doesn’t matter.

  33. colewd:
    John Harshman,

    How does this explain the evolution of a completely different strategy of providing cellular oxygen with interdependent parts?

    There is no such thing as “completely different”. That’s one problem you have. If you reject comparative biology (as one who believes in separate kinds must), there’s a lot you can’t learn.

    This is all the same subject which is how does a complex system evolve incrementally.There is no complete explanation until the origin of the genetic information to build that system is explained. Allan brought the genetic information part of the discussion in when he surfaced the Zygote analogy.

    No he didn’t. That was you, subsequently. His point had nothing to do with genetic information. And I don’t think it’s necessary to look at the genetic level. The existence of phenotypic intermediates is enough for many purposes. Sure, for a complete explanation, you need everylthing; that’s what “complete” means. But you don’t need a complete explanation to have a pretty good explanation.

  34. petrushka: Some questions are just questions. I always assumed that speciation was not triggered by accelerated rates of molecular evolution. Or more specifically, accelerated rates of mutation.

    Just curiosity.

    You have PE backwards. It isn’t accelerated mutation that’s supposed to cause speciation, it’s speciation that’s supposed to cause accelerated rates of, not mutation exactly, but fixation. PE relies on Ernst Mayr’s ideas of how speciation works, and those ideas are almost certainly very wrong.

  35. colewd:
    dazz,

    From Scientific American:

    If you continue to make bold assertions, it doesn’t matter.

    What does any of that have to do with anything?
    This is stupid even for you, Bill

  36. John Harshman: You have PE backwards. It isn’t accelerated mutation that’s supposed to cause speciation, it’s speciation that’s supposed to cause accelerated rates of, not mutation exactly, but fixation. PE relies on Ernst Mayr’s ideas of how speciation works, and those ideas are almost certainly very wrong.

    I don’t have it backwards so much a not having it. Apparently I am not alone.

    I didn’t assert anything about what is what. I asked questions for which I don’t have the answer.

  37. John Harshman,

    There is no such thing as “completely different”. That’s one problem you have. If you reject comparative biology (as one who believes in separate kinds must), there’s a lot you can’t learn.

    You have not given me a reason to accept it. Ok both “getting oxygen through the skin” and a circulatory system both involve getting oxygen inside cells but beyond that building a circulatory system is very different and requires a lot of new genetic information.

    No he didn’t. That was you, subsequently. His point had nothing to do with genetic information. And I don’t think it’s necessary to look at the genetic level. The existence of phenotypic intermediates is enough for many purposes. Sure, for a complete explanation, you need everylthing; that’s what “complete” means. But you don’t need a complete explanation to have a pretty good explanation.

    I understand your point that there is supporting phenotypic information. Since the current mechanism of choice is random genetic change followed by selection, and we know random change to a sequence will drift it toward non function, there is a big gap in the explanation. Do you believe that genotype change is responsible for change in phenotype?

    And I don’t think it’s necessary to look at the genetic level.

    Without this all you have is comparing similarities with no explanation of how they are linked except the word “evolved”. You are directly competing with the word “designed” which is how information is generated as far as we know.

  38. Mung,

    You can disagree with Gould. But using Gould to contradict those dangerous Creationists does come with a built in problem, as I pointed out.

    Yet somehow using Gould to contradict those dangerous evolutionists is A-OK? I think you are missing something central in your familiar Google-fingered rush to find Someone Who Disagrees With Evolutionist X.

    Allan Miller: There is no conflict between punctuated equilibrium and gradualism other than in the minds of people who appear not to understand one or both.

    Mung: Stephen Jay Gould comes to mind. 🙂

    Yet you can’t even answer the simple questions I posed on the subject. You stick your fingers into the Gould glove puppet and waggle them furiously, without being able to articulate an actual point. You’ve found an exception to my generalisation? Well done you.

    I’m happy to revise my statement:

    “There is no conflict between punctuated equilibrium and gradualism other than in the minds of people who appear not to understand one or both. An exception can perhaps be made in the case of Stephen Jay Gould, who specifically – but only in one sense – defines Gradualism in a manner that has PE in direct opposition to it, possibly to make PE appear more revolutionary than it really is. See Dawkins, The Blind Watchmaker Chap 9 for a critique of Gould’s position”. Dawkins argues that the version of ‘Gradualism’ Gould claims PE ‘refutes’ is held by no-one

  39. colewd,

    In this Zygote the pre existence of the information (DNA) already exists to build the complete system and the Zygote has access to oxygen through the mother until development is finished. Oxygen transport is mission critical to multicellularity and it is a interdependent complex system.

    I suggested you forget mammals (and other live births), but you seem unable to think outside of humans. Sure, oxygen is essential to a multicellular organism. Small ones, however, do not need a circulatory system. This provides an ‘in’ for incremental provision of more active systems, which then permit increase in size and complexity.

    Your imagination seems to go no further than whole systems popping into existence fully formed. I term it evolution blindness. You can’t even conceive of an evolutionary path for the sake of argument. It may be either cause or effect of your Creationism, I guess. But, if you want to critique evolution, it might help to think like an evolutionist – to anticipate what the evolutionary approach might be.

  40. colewd: Since the current mechanism of choice is random genetic change followed by selection, and we know random change to a sequence will drift it toward non function, there is a big gap in the explanation.

    No, you literally acknowledged the solution. SELECTION Random genetic change FOLLOWED BY SELECTION. So there will NOT be “sequence drift toward non function”.

    There is no gap in the explanation.

  41. colewd:
    John Harshman,
    You have not given me a reason to accept it.Ok both “getting oxygen through the skin” and a circulatory system both involve getting oxygen inside cells but beyond that building a circulatory system is very different and requires a lot of new genetic information.

    The term “new genetic information” is not well defined. It seems reasonable to me that we could define it in context as “mutations that increase fitness”. The point about the various organisms that lack circulatory systems of human complexity is that they show the plausibility of incremental steps leading from no circulatory system to yours. Given the possibility of such steps, and given the existence of random variation, natural selection would be capable of building the system. There’s your reason.

    I understand your point that there is supporting phenotypic information.Since the current mechanism of choice is random genetic change followed by selection, and we know random change to a sequence will drift it toward non function, there is a big gap in the explanation.Do you believe that genotype change is responsible for change in phenotype?

    Yes. What alternative do you propose? And Rumraket has concisely explained why there is no gap. Do you understand what natural selection is and how it works?

    Without this all you have is comparing similarities with no explanation of how they are linked except the word “evolved”.You are directly competing with the word “designed” which is how information is generated as far as we know.

    Once again, you provide no definition of “information”, and none can be extrapolated from anything you have said either. It would appear to be a magic talisman for you. We do indeed have a good explanation for how intermediates can be linked: natural selection. One can study selection acting on phenotypes without knowing the underlying genetic differences, and indeed that’s how it was done and had to be done before the advent of DNA sequencing.

    I am continually amazed at the contrast between your standard of evidence for evolution and your standard for resurrection. It appears that your standards are flexible and highly correlated with whether you already agree with the conclusions.

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