Coyne on “What Darwin Got Wrong”

Jerry Coyne has done a joint review of Dawkins’ “The Greatest Show on Earth” and Fodor and Piattelli-Palmarini’s “What Darwin Got Wrong”.  I’m not all that concerned with Dawkins’ book, and think that it might go too deep for my limited interests.  However, after reading Coyne’s review, I am interested in “What Darwin Got Wrong”, for two reasons:

1) Because after reading the review I think they might have a point.

2) Because after reading the review I wonder if they’ve also gone insane.

It’s never good to judge a book by the writings of someone who has a stake in them being wrong, since all sorts of misinterpretations can occur.   So, to tell if 2) is right, I have to read it myself to make sure that the insane claims really are insane.  But I can deal a bit with 1), by looking at what Coyne says about it and seeing if his replies might make sense against insane points but not against sane points (we might end up agreeing on the same points, oddly enough).

Coyne’s “ad” for his review is here:  http://whyevolutionistrue.wordpress.com/2010/04/22/i-review-what-darwin-got-wrong-and-the-greatest-show-on-earth-in-the-nation/

The review — and it was most gracious of the magazine to allow it to be put up for free on-line, at Coyne’s insistence, so kudos to both — is here:  http://www.thenation.com/doc/20100510/coyne/3

(We start on page 3 because that’s where I’m going to start; the previous two pages talk more about Dawkins’ book which I don’t think I’d object much to, so …)

So, let’s start with Coyne’s criticisms:

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“… let’s examine F&P’s claims. These fall into two groups. The first is that scientists have recently discovered a lot of things about genetics and development that make natural selection look ineffective:

        “Contrary to traditional opinion, it needs to be emphasized that natural selection among        traits  generated at random cannot by itself be the basic principle of evolution. Rather, there must be strong, often decisive, endogenous constraints and hosts of regulations on the phenotypic options that exogenous selection operates on.”[reformatting of the quote is my screw-up; this section is a quote from “What Darwin Got Wrong”]

In other words, Darwin’s assertion that species are “quite plastic” is wrong: organisms are so constrained by their biological nature that they’re not free to change, even if it would be good for them to do so.”

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Whoa.  Wait.  That’s not an “in other words”.  That doesn’t seem to be what F &P-P (Fodor and Piattelli-Palmarini) are actually saying.  In fact, just from that quote they seem to be saying the precise opposite: that in order for any sort of external selection to work, there has to be constraints on the organism, and so you can’t just get random changes selected for.  This seems pretty reasonable, as if it was completely random changes you could get an awful lot of changes that either didn’t relate to the previous ones that were successful or that were, in fact, fatal, and even fatal to a more developed organism.  And it seems to me that this notion of constraints is, in fact, precisely what Dawkins uses to deny that natural selection is actually “random”; you can’t get any change, but can only get changes that are allowed by the DNA expressions and structures of the organism.  You don’t just get wings, but you first get small changes, selected for, that can develop over time into radical changes, but it doesn’t just happen at random.

Now, how much this impacts the ideas on either side is an open question, but I don’t get a good feeling when even I — and, I admit, I’m not an expert in biology and, quite frankly, hate doing it, personally — can look at a quote and think that the interpretation of it is somewhat lacking.

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Let’s look at one of these: phenotypic plasticity. This refers to the ability of a phenotype–an observable trait or characteristic of an organism–to change within a single generation in response to environmental fluctuations. This is what happens, for instance, when you get a tan. If you have an outdoor cat, its fur gets thicker in winter. The plumage of Arctic animals like the ptarmigan, ermine and Arctic hare changes color from brown to white as winter comes on. Even the lowly brussels sprout has sophisticated plasticity: when it detects that a sprout-eating butterfly has laid eggs on the plant, it changes its leaf chemistry to attract parasitic wasps that destroy those eggs.

F&P imply that somehow–they’re not clear about how–this ability to undergo adaptive developmental change within a generation prevents natural selection from causing genetic change between generations. But that isn’t the case. In fact, far from being an impediment to natural selection, the ability of an individual to adapt to a changing environment is a product of natural selection! Individuals who can tan in the sun (and thus prevent melanomas) have an advantage over those whose pigmentation is fixed. Cats are better off if the length of their fur suits them to the seasons. Genes that are able to respond to predictable variation in the environment will always outcompete those that produce only a fixed (and hence episodically maladaptive) trait.”

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This might be a fair interpretation of their claim, and if this is their claim then, yes, they’re nuts.  But let me posit this: Imagine that we have a beneficial trait — say an increase in brain size — that mutates into an organism.  But, just by sheer “luck”, it happens to only propogate amongst cat-like creatures that don’t have the ability for their fur to grow thicker by the seasons.  Now, from what Coyne has just said above, we know that growing thicker fur confers an advantage.  Does it confer a greater advantage at that moment than increases in brain size?  If it does, then selection will weed it out, not because it isn’t advantageous but because it is correlated with another trait that isn’t advantageous.  Now, let’s imagine another trait, like having lighter coloured fur (so it stands out more in the environment).  But let’s say that it happens to be the case that it mainfests in the animals whose fur can thicken.  It, then, should survive as long as it is not so deterimental to the organism that it drops its survival below that of the animals that do not have the “thicken fur” trait but do have the “brain size increase” trait.

Now, it would be a fair argument to say that this case is fairly contrived, and I concede that.  My concern is that it seems to me that, in principle — at least at this time — you couldn’t tell the difference.  Why is this a problem?  Well, it means, to me, that attempts — particularly problematic in evolutionary psychology (which is where I encountered and hated it), but which seem to be common in everything dealing with evolution — to explain a trait by assuming it is beneficial and then finding an explanation for how it could have been beneficial seem pretty dangerous, and that if there is disagreement it is really hard — if not impossible — to tell who’s right.  If someone claims that a trait is a free-rider, and other people claim that it has benefits (but don’t agree on the benefits) at least for traits developed over the long term we really don’t have a way to settle that.  That’s something that should give biologists some pause, at least.  (I’ll address the examples where we can, later.  I tend to like to go in order, which can be confusing but makes my life easier [grin]).

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Indeed, virtually none of the biologists who study the “constraints” described by F&P share their dim view of natural selection. That’s because, over and over again, selection has wrought the most improbable and unpredictable changes in animals and plants. F&P claim, for example, that selection could never produce winged pigs because of developmental constraints: “Pigs don’t have wings because there is no place on pigs to put them. There are all sorts of ways you’d have to change a pig if you wanted to add wings. You’d have to do something to its weight, and its shape, and its musculature, and its nervous system, and its bones; to say nothing of retrofitting feathers.”

Haven’t F&P heard of bats? Bats evolved from small four-legged mammals, probably resembling shrews. You could say the same thing about shrewlike beasts that F&P did about pigs: how could they possibly evolve wings? And yet they did: selection simply retooled the forelegs into wings, along with modifying the animal’s weight, shape, musculature, nervous system and bones for flying (no feathers needed). One of the great joys of being a biologist is learning about the many species in nature whose evolution would appear, a priori, impossible.”

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Okay, see, I’ve read about the “pig” example, and every time I’ve read it I’ve ended up interpreting it as really this argument: “It’s not the case that pigs don’t have wings because wings aren’t beneficial to pigs, or that there was some ‘have wings’ trait that was selected out by natural selection.  Pigs don’t have wings because they’ve never, ever, exhibited a trait that could lead them to wings.  Pigs just don’t have any ‘wing-creating’ trait, and never exhibited one.  Selection only works on what can be selected for, and if a trait — even in its basic stages — doesn’t manifest it will never be selected for, no matter how beneficial it would be for the pig to fly”.  And this seems pretty reasonable to me.  Any attempt to say “pigs don’t have wings because there is/was no benefit to them developing wings” is, in fact, neither empirically nor philosophically sound.

But this in no way discredits the theory about bats.  We can in fact presume that some precursor of wings did develop in bats, and in some way that filtered through a number of adaptations until they had full wings.  Whether or not all of those — or even most of those — adaptations were selected for as opposed to being free riders seems, to me, to be an open question, but that bats did develop wings and did so gradually from shrew-like creatures is, to me, undeniable.

So, if F & P-P really do say what Coyne interprets them as saying, they’re insane … but that’s not how I’ve taken that every time I’ve read it.  I’ll have to read the book to say for certain.

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“But wait a minute. If you translate that last sentence into layman’s English, here’s what it says: “Since it’s impossible to figure out exactly which changes in organisms occur via direct selection and which are byproducts, natural selection can’t operate.” Clearly, F&P are confusing our ability to understand how a process operates with whether it operates. It’s like saying that because we don’t understand how gravity works, things don’t fall.”

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If F & P-P are really saying that nothing ever gets selected for on the basis of benefit, then they’re insane.  But I think the biggest issue is this: how can you say that natural selection is responsible for our traits when you don’t know how many of our traits were propogated through the species because they were beneficial or because they were free riders on other things?  If, say, 90% of our traits were either free riders or free riders until an environmental change made them beneficial, you can’t say that things like: brain size, consciousness, eye sight, bipedalism, opposable thumbs, etc , etc are the way they are because of natural selection, since any and all of them might have developed as free riders.  And if it could be the case that the vast majority of our traits could owe most or all of their presence to free riding, doesn’t that make natural selection less important, and other factors more so?  And so shouldn’t we stop just looking for benefits to explain traits?

Now, Coyne does have a reply to this.  Before I discuss it, I want to make it clear that I don’t deny that traits can persist and propogate because they are selected for on the basis of benefit to reproduction.  There are clearly some cases where this occurs, and Coyne’s examples may well be of such cases.  The issue, for me, really is how we determine this generally, not in specific cases.  If Coyne can prove that a specific case is certainly chosen by natural selection, then I’m more than happy to grant that case (and hope that F & P-P would as well).

So, the peppered moth:

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Here’s a more realistic example. Perhaps the most famous case of natural selection in action is the color change that occurred in Britain’s “peppered moth” over the past 150 years. Before the Industrial Revolution, these moths had white wings speckled lightly with black, although avid collectors found a few all-black mutants. As pollution from manufacturing increased the concentration of suspended particles in the air, black moths became more numerous, and eventually predominated in many places. When clean air laws reduced Britain’s pollution in the 1950s, the evolution of wing color reversed, and in most places the white color once again became common. The difference between white and black moths was shown to reside at a single gene.

What caused these evolutionary changes? There were several theories. One was that the target of selection wasn’t the moth’s color but the survival of caterpillars that, while not showing the color differences of adults, happened to be affected by the same gene. Another suggestion was that natural selection acted on color: perhaps sharp-sighted birds picked off moths whose color contrasted with that of the trees on which they rested. In unpolluted woods, lichen-covered trees are light-colored but turned black as pollution increased. This would give a selective advantage first to the dark-colored moths and then, as pollution abated, to light-colored moths.

F&P would presumably counsel us to give up at this point, since we can’t, they say, distinguish between the counterfactuals of selection “for” larval survival and “for” adult color. But we can! Breeding experiments in the laboratory showed that the survival of caterpillars couldn’t explain the increase and subsequent decline of the black form. In contrast, field experiments that involved observing predation on dead moths of different colors fastened to trees of different colors, and on live moths of different colors released in unpolluted woods, showed that selection on color was strong, easily able to explain the evolutionary changes observed in nature.”

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I think this is a pretty strong case, so let me nitpick that last statement a bit: his claim is that the observations showed that colour is able to explain it.  Does that mean that that is what happened?  What if there was an unobserved gene that simply allowed black moths to better survive in polluted areas than the whiter ones?  You might still see selection by predation, but that wouldn’t be what was doing most of the work, even if the claim was that it was strong enough to do so.  How would we test this claim?

And this is in a case where we have lots of readily available data, and one could still raise — pointless, I admit — doubts.  Now, let’s take the list of traits that humans or even pigs have.  For how many of them could we do that sort of analysis?  How many of them can we prove exist only because of a benefit?  The stegosaurus example is not the only case where we really have no way of proving it, one way or the other.

See, there’s an additional problem here.  To be selected for, a trait has to develop.  And so someone might be able to find a case where that trait did develop because of a benefit.  But it has to be in the gene pool first, which means it has to a) manifest and b) survive.  Take our black-coloured moths.  There were black-coloured moths — as far as I know — before the industrial evolution.  It wasn’t the most common trait, but it was there.  So why was it there?  Because it benefitted?  Unlikely, and absolutely false if Coyne’s explanation is the right one.  So black colouring, then, was a free rider that simply happened to end up beneficial when the environment changed.  So, then, it is reasonable to ask what the peppered moth is an example of?  The trait is not explained by natural selection, but the numbers of individuals with that trait is.  I suspect that F & P-P want explanations for why they have that trait (black-colouring) and don’t really care about why most moths don’t exhibit that one.  And the explanation given, it seems to me, doesn’t explain how they got that trait in the first place (and, interestingly, seems to work against it).

So, if we have a trait that is bad enough to limit the number of organisms but survives anyway, then it seems that “selection” didn’t operate on that trait.  How many of these traits do we have?  I don’t know, but I’m not convinced that anyone else does either.

A quick final comment about artificial versus natural selection.  Artificial selection dodges all of these issues because it selects for specific traits: the breeding and culling are aimed precisely at getting that specific trait to manifest.  Natural selection, as F & P-P point out, does not.  It aims at getting an organism that reproduces.  Because of this, artifical selection as an explanation for why a specific trait is as it is is a good and reasonable and testable and settleable explanation.  But with natural selection, all we have is “It lived and reproduced”.  We don’t know why.  We don’t know if it was the trait that we are looking at that made the difference or if it played any real role at all in the survival and reproduction.  There is an intensely complicated relationship between all the traits in an organism and its environment that confuses things.

In essence, you can’t apply natural selection explanations to one trait alone.   You always have to consider all the traits and the envionment the organism it was in to get an explanation for any particular trait.  If F & P-P want to simply draw attention to that, I’m on their side.  If they want to claim that therefore natural selection never happens, they’re insane.  And without invoking the Fallacy of the Golden Mean, from both my experience and from my reading I strongly suspect that the real point is somewhere in between.  Heuristically speaking, it usually is.

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8 Responses to “Coyne on “What Darwin Got Wrong””

  1. Hardlyhome Says:

    You say: “that in order for any sort of external selection to work, there has to be constraints on the organism, and so you can’t just get random changes selected for.”

    I read the quote closer to Coyne but anyway… sorry but I don’t really get what you mean here? Can you be a bit more specific about what type of random changes you are talking about here, genetic or phenotypic? If you mean genetic, why not?

    The free-rider argument seems a bit silly to me. Exactly how is one trait free-riding on another? The actual mechanism? And anyway, in your examples, why does it have to be either/or? Why can’t there be a fluctuation of the relative proportions of the two alleles over time as selection pressures vary?

    Have you seen any real examples of someone saying something as silly as “pigs don’t have wings because there is/was no benefit to them developing wings” ? I don’t think I have.

    You say (in the bit about peppered moths): “So black colouring, then, was a free rider that simply happened to end up beneficial when the environment changed. ” No black colouration was not a free rider at all it is a genetic mutation that is fairly common from what I have read. Because it is a common mutation there is always a small number of new mutants sporting a black coat. No free rider at all.

    Then you say:”So, then, it is reasonable to ask what the peppered moth is an example of? The trait is not explained by natural selection, but the numbers of individuals with that trait is. I suspect that F & P-P want explanations for why they have that trait (black-colouring) and don’t really care about why most moths don’t exhibit that one. And the explanation given, it seems to me, doesn’t explain how they got that trait in the first place (and, interestingly, seems to work against it).”

    The peppered moth is used an example of natural selection in text books.
    The original trait is the black colouring. That is explained by mutation not selection. The selection bit comes with the relative frequencies of the two alleles. The explanation is one of selection causing the changing frequencies of the two alleles not how the allele came to be in the first place.

    You again:”So, if we have a trait that is bad enough to limit the number of organisms but survives anyway, then it seems that “selection” didn’t operate on that trait. How many of these traits do we have? I don’t know, but I’m not convinced that anyone else does either.”

    The particular mutation that gives rise to the mellanic form is a fairly common mutation just as some of the haemophilia mutations in humans are fairly common. That’s why the trait survives under non-ideal conditions. And anyway, how quickly a trait dies out depends on many things including the size of the selection pressure. If the selection pressure is not that great the trait can hang around in small numbers for a long time.

    As to your last couple of paragraphs, I get the distinct impression you are confusing popular explanations with what biologists actually say between themselves. ISTM that the simplistic explanation you give in the last couple of paragraphs is just that, overly simplistic and not the sort of thing a biologist is ever going to say when he\she is being careful about their arguments. Lies-to-Children and all that. Of course we don’t *know* that any of the reasons given are totally correct, that goes without saying. Or at least it should.

    The first three sentences of your last paragraph, sorry mate I don’t want to sound juvenile but (I’m going to) DUH. Why do you think the same few examples keep getting trotted out over and over and over. Because real life is complicated and messy and it is really difficult to find examples that are as clear cut as the peppered moth example is. If you think biologists aren’t saying that then you aint listening.

    Have fun,
    Craig

  2. verbosestoic Says:

    As to your first point, it’s just that you aren’t getting complete randomness. There are constraints in DNA and what it can express and in what traits can be expressed from what point you’re at, at least directly. I’m not well-versed in the details, not being a biologist, but I do recall that Dawkins makes a big deal over it in “The God Delusion” with that exact same sort of wording. But, in short, my impression is that you aren’t just randomly tossing ANYTHING out, and so it reduces the improbability of getting to that final state starting from the supposed initial states.

    I’m also not getting into any sort of mechanisms of free-riding, but free-riding would be cases where an organism has a beneficial trait and other traits that that organism has that don’t in and of themselves have survival or reproductive value propagate because they are in an organism that reproduces — or reproduces more — because of that beneficial trait. There’s no requirement for the traits to be directly linked, but they can be.

    I don’t think that anyone has used that precise example — although some of the comments in reply to the review came close — but I have heard of arguments in at least evolutionary psychology that are that bad. I’m not sure how far it extends past evolutionary psychology but if they are misusing evolution, one would think that Coyne and others would correct them as to what evolution entails, and make it clear that normal evolutionary reasoning doesn’t fall victim to the same traps.

    I’m not clear how you’re using the term “mutation”, or how you’re claiming that the black colouring was the original colouring. First, I only consider mutation to be an actual change to the genes themselves. Blue eyes are not, to me, considered a mutation but are instead an actual trait that is in the minority. If selection was the explanation FOR the traits, we would expect to be able to claim that the trait of “black colouring” exists because it was beneficial. But it isn’t beneficial, so why did that trait develop and why does it survive? Well, it might in some sense be recessive, but that causes issues with the number changes when there was more pollution. So what is the underlying reason why there can be black coloured peppered moths?

    I did concede that the numbers is explained by selection, but do think that they are more interested in explanations for the TRAIT, not just its frequency in the population. And it is a free rider since, as proven, it is NOT beneficial, and therefore it must exist because of other factors that it can use to continue to propagate. Which might not be the sort of free-riding that I outline above, I concede, but it is something other than selection for benefit.

    If the popular impression is not accurate, then biologists — and Coyne — should simply be saying “That’s what is sometimes said, but it isn’t what we do” and taking at least part of the responsibility for not using their own terms clearly outside of their own field. If you aren’t taking care to ensure that your terms are properly used, you don’t get to complain when people get them wrong.

    Even the peppered moth seems a more complicated case than it seems, depending on the explanation one is looking for and the definition one is using for things like “mutation”. If you do understand that, then all you need to say is “We already do that”.

  3. Hardlyhome Says:

    Can you please tell me what you think the “random” in “random mutation” actually means to a biologist because I don’t think you have it quite right. The definition of mutation I’m using is the same as yours, I just get the impression that you don’t quite grasp the way the word random is being used.

    Free riding without a mechanism is also a bit silly. You are positing a phenomena that you seem to believe may, at least, be very significant. So significant that it questions the very basis of the theory of evolution. Or at least much of the way it is taught. If you haven’t got a mechanism for this to happen I don’t see where this idea can possibly go. It is the mechanisms of evolution that are so important after all. If there is no mechanism by which traits can be linked in this way, how do you go about defending the belief in it?

    Could you give me an example of something as silly as the quote I asked you about in evolutionary psychology please because I’d like to know what sort of thing you mean. I’m a bit up in the air about it myself but I think it may have *some* merit. Not sure.

    Sorry didn’t mean to give that impression re mellanic form. What I meant was that the actual mutation that causes the mellanic form is a very common, very simple mutation that happens all the time. That is why the trait of black body colour keeps coming up for it to be selected. In the past the rate of survival of this form was very low because it was at a disadvantage, therefore not very many would have reproduced at all, keeping the proportion of black moths at or very close to the mutation rate. When the environment changed, however, the mellanic form was no longer at such a disadvantage. Therefore it’s numbers increased. Then when the environment became cleaner again, it was at a greater disadvantage again, therefore it’s number reduced. The mutation keeps coming up all the time but the environment it lived in had changed. Therefore the selection pressures changed and therefore the relative proportions the the two morphs changed. No free riding at all just very simple random mutation producing the mutated allele and natural selection changing the relative proportions of the two forms.

    Blue eyes are not a mutation, correct. They are a trait, again correct, but the genetic change that produces blue eyes *is* a mutation. In exactly the same way, the mellanic form is a trait but the change that produces the mellanic form is a mutation. Selection is not the explanation FOR the trait. Mutation is the explanation for the trait. Selection is the explanation for the *relative prevalence* of the trait. So mutation is the explanation for the black morph and selection is the explanation for the change in frequency of the morph. Changing frequency as the environment it lives in changes. If F & P-P are trying to use selection to understand the *existence* of the mellanic trait they are batshit crazy.

    Have you read any Terry Pratchett? Particularly the first of the Science of Discworld books? If so, then you know that “Lies To Children” is a much bigger problem than just in biology. If not then I recommend you do. You will find much to agree with and much to disagree with. And it’s bloody funny as well. Anyway, where was I.. Oh yes. Yes maybe Coyne should be more careful and correct his commenter’s more often but, really, there is only so many hours in the day. And does every sentence out of a scientists mouth have to start with the same disclaimer every single time? It would get very boring to listen to.

    Have fun,
    Craig

  4. verbosestoic Says:

    Well, I’ll quote from one of my critiques of “The God Delusion”, but unfortunately I don’t have where the argument was originally made:

    “A better argument that I’ve heard (and it may even be in here, but I didn’t find it in my quick read through around where the issue is introduced when I realized I wanted to address it; Dawkins does a very good job of hiding his real arguments amongst the platitudes and odes to natural selection) is that it isn’t quite by chance because the mechanisms are constrained; sexual selection can only select from the available traits (even though that’s sort of random, but also constrained) and in general DNA only encodes for certain traits; the flipping has to flip to something that the organism can understand how to produce when it builds the offspring. So things aren’t really random, and so aren’t really by chance.”

    Note that I DO consider this to count as random, and don’t think this really works to address the criticisms of the randomness of the process. However, this does work for F & P-P since all they’re saying is that natural selection is, in fact, constrained; there are traits that a certain organism at a certain time will NOT be able to manifest because of those constraints.

    I hope you aren’t going to deny that free riding occurs. I also think that you’re overstating my position. I don’t deny natural selection, but do wonder if appealing to it — or benefit — for why a specific trait occurs may be problematic.

    As for mechanism, there would be multiple mechanisms. One would be cases where an organism has trait A that is really beneficial, and trait B that is either neutral or mildly detrimental. A’s overall fitness is better, so it reproduces, and B goes along with with, free riding. B may eventually itself become beneficial.

    As for dumb arguments, I did come across a debate — in a class — where there was talk about cheaters and cheater detectors and a lovely cycle of benefit causing cheater detectors to “evolve”, for which there is no evidence and which would be conscious adjustment for most of the time that detecting cheaters would matter. I also have issues with deriving altruism from benefit in the same way, as it has the same issues AND refutes it being altruistic if we ever become consciously aware that it benefits us. Are these as bad? Maybe not, but they hint to me the problem that’s being addressed here: we leap to any sort of benefit explanation and have no way of determining what the actual benefit is or, in fact, if there even is one.

    Now, about the whole mutation thing, note that I conceded that natural selection explains the numbers but not the existence of the trait, and argue that F & P-P want to explain why we have a trait and not others. So why are those moths white and blackish, but never purple? Can we just never get that sort of mutation, or does it just never survive? And so on.

    If the popular impression of evolution is incorrect, and Coyne is aware of that, then he should spend less time insulting F & P-P for getting it wrong and more time pointing out that, yeah, based on that they’re view is right but most of the problems they’re addressing are addressed at the actual scientific level. You don’t get to insult people for getting something wrong that is, in general, not explained very well.

  5. Hardlyhome Says:

    Sorry mate but your first couple of paragraphs don’t really explain to me what you think the word “random” means in the phrase “random mutation”, so I’ll give you my understanding and we can see how much you agree with. The word random means, specifically, that the *direction* of any mutation is not directed by any force at all. Any mutation that occurs in a gene does so according *only* to natural chemical and physical laws not because there is any other reason for the mutation. That is all it means. Nothing else. I get the impression that you seem to think there is some part of natural selection that is random? Natural selection is the exact opposite of random. It is natural selection that is *placing* constraints on what is developing, living and growing. If I have misunderstood you and you agree with all of the above I apologise but some of the things you say don’t make any sense to me if you understand the terms the way I do. For example, I don’t understand how you could say “…since all they’re saying is that natural selection is, in fact, constrained;…” because it is natural selection that is doing the constraining in the first place. And “…sexual selection can only select from the available traits (even though that’s sort of random, but also constrained)” doesn’t make much sense with correct ideas either. There is nothing random about any form of selection, sexual or natural.

    No of course I don’t deny free riding occurs, but I do have a great deal of trouble with the idea that it is significant. Particularly that it is significant enough to question much of evolutionary theory. Just think about your body and what part of it could be significantly injured and you still survive on a savannah a million years ago. There isn’t much spare that you could afford to lose is there? That leads me to believe that pretty much every part of a body is under significant selection pressures at all times. If I’m overstating your position I’m sorry. I didn’t do that as some cheap rhetorical trick it was genuinely what I thought you believed.

    As for mechanism, what I’m after is exactly *how* “…B goes along with…” What is the mechanism that forces or requires or even allows B to go along with A. That’s the mechanism I feel you are missing and really, really need to explain.

    When evaluating ideas from sociobiology, please don’t take them as if all biologists unequivocallly accept them. They don’t. The discipline has only been around forty years and I don’t think there are many who think any of their arguments are anything more than speculation. Speculation they may think has real merit but they don’t take them as more than that. You’re right, there is bugger all evidence for them and that has been one of the biggest problems getting them accepted. If you don’t like the arguments fair enough I can understand that. To me some of them make sense. But again, should every sentence from a scientist carry the standard scientific disclaimer?

    The other thing is that in your example of cheaters and cheater detectors, it’s not that the cheaters caused cheater detectors to evolve at all. How could they? What they mean is that the presence of cheaters caused an evolutionary pressure that meant cheater detectors have an advantage over non cheater detectors. The presence of cheater detectors then produced a selection pressure making being a better cheater an advantage. This, of course, caused a selection pressure that made being a better detector and advantage and so on ad infinitum. Now you’re right there is no evidence for this at all, behaviours don’t fossilise. But this doesn’t sound all that silly to me.

    I get to quote from a real scientific paper printed in a real journal here. From the “Journal of Heredity 2004:95(2):97–102” which you can find here http://bsgran.people.wm.edu/AllelicMelanism.pdf we get
    “The darkest melanic phenotype, named carbonaria, is nearly solid black and is easily distinguished from the much paler typical form (wild type) of the moth. Phenotypes that are intermediate between typicals and carbonaria are called insularia. The phenotypic differences result from multiple alleles at a single locus that exhibit an approximate dominance hierarchy: the carbonaria allele shows complete dominance over the insularia and typical alleles, and the several insularia alleles show incomplete dominance over the typical allele (Lees and Creed 1977).”
    So what we have is one single gene that, at least partially, controls coat colour. Only the mutations to this gene will change the moths colour in this way. So why do we get only a few colour choices and not hundreds? Simple. This gene controls the amount of the pigment melanin produced in the animals coat. Nothing else. If melanin is produced in all cells the animal is all black. If produced in some then the animal isn’t all black. That’s why we don’t get purplish ones because the pigment only produces one colour, black. This is why we need the various fields of biology to look at these questions. The answers are in biology and the devil is in the detail. Not that philosophers don’t have anything to add to the debate. They can make the coffee. 🙂

    Popular impressions and a book by academics are two completely different things. What Coyne says to the populace should be very different to what he says to two academics writing a book criticising things he understands and they obviously don’t. Do you really think it’s right to hold two academics to the same low standards as lay people?

    Have fun,
    Craig

  6. verbosestoic Says:

    Phrasing parts of it like “selection” might have confused things, so let me clarify things by referring strictly to sexual selection:

    Selection in sexual selection — ie picking a sexual partner — isn’t random.

    The traits that come FROM sexual selection — through sexual reproduction — are, even though constrained.

    And it isn’t the case that natural selection is the big constraint here, or at least that’s not a safe argument. Natural selection can only select on the traits that do, in fact, appear. So natural selection has never worked on “purple peppered moths”, because as you point out it’s the fact that melanin cannot take on that colour that means that purple just isn’t a colour for those moths. You’d have to rework the entire mechanism of moth colouring to get purple moths.

    Which, I think, is the purpose of the “pigs with wings” example. Yes, pigs could have evolved wings. However, the way they went built them a structure that doesn’t allow for wings. You’d have to do major re-working to get pigs with wings. Could this happen under the right conditions over thousands of years? Perhaps, but it’s hard to see why it would or what environmental conditions could kick that whole process off.

    Additionally, natural selection can only work on things that have significant benefit or detriment to the organism. If the change is too slight, while some small number will reproduce more or less because of it that won’t be enough to really change the traits the organism has. And we can see this in the peppered moths, since we’ve proven that black colouring IS detrimental and yet such moths still do exist.

    This is why the peppered moth really isn’t — in my mind — a good example against F & P-P, if they’re at all sane. You can’t appeal to benefit to explain why there are black moths, because it normally isn’t a benefit to be a black moth. You end up appealing to underlying processes like recessive genes and mutation to get it. And that leaves the strict definition of “natural selection” that you use in the first paragraph out.

    Which is kinda the point, and all that I’m after. I’m after showing that it is a bad argument to — when trying to explain a trait — simply find a benefit for a trait and declare the trait explained. I don’t care much about the specific sociobiological arguments, but far more about the underlying way it’s done. Imagine, for example, that one theory says that the trait had benefit B1, another theory says that it has benefit B2, and a third says that it was a neutral free rider. How could you tell the difference between the two, to settle on one? If you can’t tell whether a trait even HAD a benefit or not, maybe you should reconsider a paradigm that relies on showing just that.

    I don’t think it is any accident that these philosophical objections are being raised when this view is coming into contact with Cognitive Science, one of the few areas where biology and philosophy are both still interested. Philosophers are now pointing out potential issues with the arguments, and how maybe the methodology and conceptual analysis is not done as well as they might have hoped. Biologists may counter with “Well, it works”, but maybe it doesn’t work well-enough.

    This holds with your counters to free-riding. There are, as I said, multiple mechanisms for potential free-riding. I gave you one, but there are others. I gave you the simplest one, that requires no actual linking between the two. Also, F & P-P give additional examples of things that might constrain what natural selection has available to select for. We don’t need to work out the science in detail to raise an alarm that these things are worth looking at.

    As for the popular impression, Coyne certainly should speak different to people inside his field as opposed to outside his field. F & P-P — as we are generally pointedly reminded — are NOT in his field, but his field is encroaching on theirs (which is what has them so irritated). If the simple version is causing grief for people not deeply in the know, then Coyne should simply be saying “Yeah, you have a point, we know, and we’ve corrected for it” as opposed to simply saying that they have no clue what they’re talking about and so aren’t worth listening to. It strikes me that Coyne’s reply reveals more about his own frustration than real problems in their argument, although in some cases they do seem to overstate their case and take it too far.

    Now, I’ll have to read their book to see if Coyne’s criticisms are really reasonable or not, as I’ve said a number of times.

  7. Another review of “What Darwin Got Wrong” … « The Verbose Stoic Says:

    […] (My post is here, if anyone wants to refresh their memory: https://verbosestoic.wordpress.com/2010/04/23/coyne-on-what-darwin-got-wrong/ ) […]

  8. Sing my Angel! « The Verbose Stoic Says:

    […] about when to him she didn’t, she got a harsh reaction. You can look at the reaction to Fodor and Piattelli-Palmarini’s “What Darwin Got Wrong” to see just how well evolutionary biologists reacted to those laypersons — who are far less […]

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