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There is no neutral theory of evolution

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Further to“Is there a real neutral theory of evolution?”, apparently U of T’s Larry Moran responded to Vince Torley so as to make clear that he has no serious quarrel with schoolbook Darwinism:

My verdict: An embarrassing climb-down for Professor Moran

Reading Professor Moran’s post, I was struck by its muted tone. Moran believes that “some evolution at the morphological level can be attributed to … random genetic drift,” including “neutral morphological changes and a small percentage of detrimental morphological changes.” He admits that “Neutral Theory and random genetic drift … are not very good at explaining most adaptations,” adding that “the vast majority of complex structures seem to be adaptations of one sort of another.” He then tentatively proposes that “there are many ‘functions’ and ‘behaviors’ that are neutral,” but concedes that “it’s difficult to rule out any adaptive component.” He finally acknowledges that “natural selection plays an important role in the origin of most complex structures and novel adaptive morphological features,” but goes on to suggest that “there are likely to [be] many ‘novel morphological features’ that are non-adaptive.” However, since Professor Moran has already conceded that “the vast majority of complex structures seem to be adaptations of one sort of another,” it is difficult to know what to make of his last suggestion.

How about this: There is no neutral theory of evolution, but there are evolutionary biologists who wish there were. And as soon as they reveal the fact that they might be considering escape plans, thy have to backtrack. It’s okay, This is what retirements are for.

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11 Replies to “There is no neutral theory of evolution

  1. 1
    Mung says:

    There is a neutral theory of evolution and it is better at explaining the facts than neo-Darwinism.

  2. 2
    Piotr says:

    It’s amazing that after all the explanations given so far some folks are still unable to understand that natural selection (adaptive evolution) and random drift (neutral evolution) are not mutually exclusive but rather complementary. If somebody emphasises the importance of neutral evolution, it doesn’t mean denying that selection is a real and important process.

  3. 3
    gpuccio says:

    Piotr:

    The real problem is not that they are “mutually exclusive”. Obviously, they are not.

    The problem is that they are different things, and that there is a repeated shift from one to the other when we ask which of them is responsible for functional information in biology.

    The traditional view, defended also by Matzke and by you, is that NS is responsible for that. In that case, neutral evolution is irrelevamt for biological function.

    Others, like Moran and Nei, seem to suggest an important role for neutral evolution in generating function. Even if they do not exclude the importance of NS.

    Shifting from one model to the other is a smart way to elude analysis. It’s certainly easier to analyze and falsify a well defined model, rather than a slipping one.

    The simple truth is that neither can explain functional information, but for different reasons.

  4. 4
    Piotr says:

    The problem is that they are different things, and that there is a repeated shift from one to the other when we ask which of them is responsible for functional information in biology.

    No, they are not “different things”. They are two components of the same thing — the variable survival of alleles. Drift is the purely random component (accidental sampling error) and selection is the bias (in response to environmental and “internal” pressures).

    The traditional view, defended also by Matzke and by you, is that NS is responsible for that. In that case, neutral evolution is irrelevamt for biological function.

    You are putting things in my mouth (and I suppose Nick’s, too). I don’t think anyone in the field seriously doubts that selection is the main engine of the spread and fixation of adaptations, which doesn’t mean that it’s the sole explanation of them (it certainly isn’t responsible for their origin), or that neutral evolution is irrelevant.

    Note that in real populations drift and selection always act in combination. For example, whether an innovation with a positive selection coefficient has a chance to spread depends on the relative strength of selection against drift. In nearly neutral evolution drift will often override selection, but still the probability of fixation is slightly influenced by the fact that the mutation is not entirely neutral. It isn’t a question of switching between one or the other mode. They are both present.

    Others, like Moran and Nei, seem to suggest an important role for neutral evolution in generating function. Even if they do not exclude the importance of NS.

    I haven’t read Nei yet, but I agree with a lot of what Larry Moran says (not that my amateurish agreement carries much weight). Even if the non-random selection component is primarily responsible for the fixation of adaptive changes, its operation is constrained by mutations (which don’t happen just because they are needed) and may be helped along by neutral evolution (which prepares the scene for adaptive changes).

    Shifting from one model to the other is a smart way to elude analysis. It’s certainly easier to analyze and falsify a well defined model, rather than a slipping one.

    Your “slipping model” is a strawman. We can calculate the expected effects of drift and selection, depending on things like the size and structure of populations.

    Population genetics is one model taking into account both components (and much more).

    The simple truth is that neither can explain functional information, but for different reasons.

  5. 5
    Piotr says:

    I forgot to comment on the last paragraph. It’s perhaps just as well, so all right, no comment.

  6. 6
    Joe says:

    Piotr, neither natural selection nor drift actually do anything. That is what you don’t realize. And population genetics does not model reality. No one knows how long it takes to get a new allele to fix.

  7. 7
    phoodoo says:

    Mung,

    I don’t get it, whether mutations that crop up are somewhat beneficial at a certain time, or just meaningless, aren’t both ideas about equally weak in explaining how you can build a complicated well working structure?

    What’s all the fuss, neither makes any sense. The mutations still have to be sequential and combine together into something very sophisticated-both are far flung stories.

    Its like saying, do you think wolverines are

    1. sublime

    or

    2.essential.

    Where is the choice for none of the above?

  8. 8
    Mung says:

    phoodoo, don’t worry about it too much. Many of my posts are cryptic. They are intended only for the initiated.

    But I will give you a nudge in the right direction.

    Neutral theory was developed to explain something. What was it that neutral theory proposed to explain?

    Why couldn’t that “it” be explained by Darwinian theory?

    What was Darwinian theory developed to explain.

    Of the two, which explains better that which it was intended to explain, neutral theory or Darwinian theory?

    In my opinion, neutral theory offers a better explanation of what it was intended to explain than Darwinian theory offers of what it was intended to explain.

    I obviously also disagree with the title of the OP. There is a neutral theory of evolution. In fact, it’s a better theory than Darwinism, but we don’t get sensational headlines title “There is no Darwinian theory of evolution!”

    Sadly

    Thus the comment @ 1.

    Sorry, but that’s just how my mind works!

    🙂

    (Not that anyone would ever want to take a deeper look into my mind than what was just offered!)

    YECH!

    warned you!

  9. 9
    Mung says:

    Piotr, are you certain you’re not confusing the neutral theory of evolution with genetic drift?

  10. 10
    phoodoo says:

    Mung,

    Yea, I am just trying to get at what the heart of this discussion on five different threads is about. I am totally confused. How could phenotype evolution be caused by anything but mutation? Where is the disagreement amongst evolutionists?

    You get some mutations, they either last or they don’t for whatever reason. Then you get a few more mutations. That is the whole gist of evolutionary theory. What is the debate about? I can’t see anyone explaining why this is even an important point.

    The distinction of whether or not a mutation starts out as very useful is small and meaningless. The important point is are the mutations teleological. I think the odds suggest they almost would have to be.

  11. 11
    Mung says:

    phoodoo:

    How could phenotype evolution be caused by anything but mutation? Where is the disagreement amongst evolutionists?

    Well, if you’re a neo-Darwinist, the cause is natural selection.

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