Evo-Info 3: Evolution is not search

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Introduction to Evolutionary Informatics, by Robert J. Marks II, the “Charles Darwin of Intelligent Design”; William A. Dembski, the “Isaac Newton of Information Theory”; and Winston Ewert, the “Charles Ingram of Active Information.” World Scientific, 332 pages.
Classification: Engineering mathematics. Engineering analysis. (TA347)
Subjects: Evolutionary computation. Information technology–Mathematics.

Marks, Dembski, and Ewert open Chapter 3 by stating the central fallacy of evolutionary informatics: “Evolution is often modeled by as [sic] a search process.” The long and the short of it is that they do not understand the models, and consequently mistake what a modeler does for what an engineer might do when searching for a solution to a given problem. What I hope to convey in this post, primarily by means of graphics, is that fine-tuning a model of evolution, and thereby obtaining an evolutionary process in which a maximally fit individual emerges rapidly, is nothing like informing evolution to search for the best solution to a problem. We consider, specifically, a simulation model presented by Christian apologist David Glass in a paper challenging evolutionary gradualism à la Dawkins. The behavior on exhibit below is qualitatively similar to that of various biological models of evolution.

Animation 1. Parental populations in the first 2000 generations of a run of the Glass model, with parameters (mutation rate .005, population size 500) tuned to speed the first occurrence of maximum fitness (1857 generations, on average), are shown in orange. Offspring are generated in pairs by recombination and mutation of heritable traits of randomly mated parents. The fitness of an individual in the parental population is, loosely, the number of pairs of offspring it is expected to leave. In each generation, the parental population is replaced by surviving offspring. Which of the offspring die is arbitrary. When the model is modified to begin with a maximally fit population, the long-term regime of the resulting process (blue) is the same as for the original process. Rather than seek out maximum fitness, the two evolutionary processes settle into statistical equilibrium.

Figure 1. The two bar charts, orange (Glass model) and blue (modified Glass model), are the mean frequencies of fitnesses in the parental populations of the 998,000 generations following the 2,000 shown in Animation 1. The mean frequency distributions approximate the equilibrium distribution to which the evolutionary processes converge. In both cases, the mean and standard deviation of the fitnesses are 39.5 and 2.84, respectively, and the average frequency of fitness 50 is 0.0034. Maximum fitness occurs in only 1 of 295 generations, on average.

I should explain immediately that an individual organism is characterized by 50 heritable traits. For each trait, there are several variants. Some variants contribute 1 to the average number offspring pairs left by individuals possessing them, and other variants contribute 0. The expected number of offspring pairs, or fitness, for an individual in the parental population is roughly the sum of the 0-1 contributions of its 50 traits. That is, fitness ranges from 0 to 50. It is irrelevant to the model what the traits and their variants actually are. In other words, there is no target type of organism specified independently of the evolutionary process. Note the circularity in saying that evolution searches for heritable traits that contribute to the propensity to leave offspring, whatever those traits might be.

The two evolutionary processes displayed above are identical, apart from their initial populations, and are statistically equivalent over the long term. Thus a general account of what occurs in one of them must apply to both of them. Surely you are not going to tell me that a search for the “target” of maximum fitness, when placed smack dab on the target, rushes away from the target, and subsequently finds it once in a blue moon. Hopefully you will allow that the occurrence of maximum fitness in an evolutionary process is an event of interest to us, not an event that evolution seeks to produce. Again, fitness is not the purpose of evolution, but instead the propensity of a type of organism to leave offspring. So why is it that, when the population is initially full of maximally fit individuals, the population does not stay that way indefinitely? In each generation, the parental population is replaced with surviving offspring, some of which are different in type (heritable traits) from their parents. The variety in offspring is due to recombination and mutation of parental traits. Even as the failure of parents to leave perfect copies of themselves contributes to the decrease of fitness in the blue process, it contributes also to the increase of fitness in the orange process.

Both of the evolutionary processes in Animation 1 settle into statistical equilibrium. That is, the effects of factors like differential reproduction and mutation on the frequencies of fitnesses in the population gradually come into balance. As the number of generations goes to infinity, the average frequencies of fitnesses cease to change (see “Wright, Fisher, and the Weasel,” by Joe Felsenstein). More precisely, the evolutionary processes converge to an equilibrium distribution, shown in Figure 1. This does not mean that the processes enter a state in which the frequencies of fitnesses in the population stay the same from one generation to the next. The equilibrium distribution is the underlying change­less­ness in a ceaselessly changing population. It is what your eyes would make of the flicker if I were to increase the frame rate of the animation, and show you a million generations in a minute.

Animation 2. As the mutation rate increases, the equilibrium distribution shifts from right to left, which is to say that the long-term mean fitness of the parental population decreases. The variance of the fitnesses (spread of the equilibrium distribution) increases until the mean reaches an intermediate value, and then decreases. Note that the fine-tuned mutation rate .005 ≈ 10–2.3 in Figure 1.

Let’s forget about the blue process now, and consider how the orange (randomly initialized) process settles into statistical equilibrium, moving from left to right in Animation 1. The mutation rate determines

  1. the location and the spread of the equilibrium distribution, and also
  2. the speed of convergence to the equilibrium distribution.

Animation 2 makes the first point clear. In visual terms, an effect of increasing the mutation rate is to move equilibrium distribution from right to left, placing it closer to the distribution of the initial population. The second point is intuitive: the closer the equilibrium distribution is to the frequency distribution of the initial population, the faster the evolutionary process “gets there.” Not only does the evolutionary process have “less far to go” to reach equilibrium, when the mutation rate is higher, but the frequency distribution of fitnesses changes faster. Animation 3 allows you to see the differences in rate of convergence to the equilibrium distribution for evolutionary processes with different mutation rates.

Animation 3. Shown are runs of the Glass model with mutation rate we have focused upon, .005, doubled and halved. That is, uʹ = 2 ⨉ .005 = .01 for the blue process, and uʹ = 1/2 ⨉ .005 = .0025 for the orange process.

An increase in mutation rate speeds convergence to the equilibrium distribution, and reduces the mean frequency of maximum fitness.

I have selected a mutation rate that strikes an optimal balance between the time it takes for the evolutionary process to settle into equilibrium, and the time it takes for maximum fitness to occur when the process is at (or near) equilibrium. With the mutation rate set to .005, the average wait for the first occurrence of maximum fitness, in 1001 runs of the Glass model, is 1857 generations. Over the long term, maximum fitness occurs in about 1 of 295 generations. Although it’s not entirely accurate, it’s not too terribly wrong to think in terms of waiting an average of 1562 generations for the evolutionary process to reach equilibrium, and then waiting an average of 295 generations for a maximally fit individual to emerge. Increasing the mutation rate will decrease the first wait, but the decrease will be more than offset by an increase in the second wait.

Figure 2. Regarding Glass’s algorithm (“Parameter Dependence in Cumulative Selection,” Section 3) as a problem solver, the optimal mutation rate is inversely related to the squared string length (compare to his Figure 3). We focus on the case of string length (number of heritable traits) L = 50, population size N = 500, and mutation rate uʹ = .005, with scaled mutation rate uʹ L2 = 12.5 ≈ 23.64. The actual rate of mutation, commonly denoted u, is 26/27 times the rate uʹ reported by Glass. Note that each point on a curve corresponds to an evolutionary process. Setting the parameters does not inform the evolutionary search, as Marks et al. would have you believe, but instead defines an evolutionary process.

Figure 2 provides another perspective on the point at which changes in the two waiting times balance. In each curve, going from left to right, the mutation rate is increasing, the mean fitness at equilibrium is decreasing, and the speed of convergence to the equilibrium distribution is increasing. The middle curve (L = 50) in the middle pane (N = 500) corresponds to Animation 2. As we slide down the curve from the left, the equilibrium distribution in the animation moves to the left. The knee of the curve is the point where the increase in speed of convergence no longer offsets the increase in expected wait for maximum fitness to occur when the process is near equilibrium. The equilibrium distribution at that point is the one shown in Figure 1. Continuing along the curve, we now climb steeply. And it’s easy to see why, looking again at Figure 1. A small shift of the equilibrium distribution to the left, corresponding to a slight increase in mutation rate, greatly reduces the (already low) incidence of maximum fitness. This brings us to an important question, which I’m going to punt into the comments section: why would a biologist care about the expected wait for the first appearance of a type of organism that appears rarely?

You will not make sense of what you’ve seen if you cling to the misconception that evolution searches for the “target” of maximally fit organisms, and that I must have informed the search where to look. What I actually did, by fine-tuning the parameters of the Glass model, was to determine the location and the shape of the equilibrium distribution. For the mutation rate that I selected, the long-term average fitness of the population is only 79 percent of the maximum. So I did not inform the evolutionary process to seek out individuals of maximum fitness. I selected a process that settles far away from the maximum, but not too far away to suit my purpose, which is to observe maximum fitness rapidly. If my objective were to observe maximum fitness often, then I would reduce the mutation rate, and expect to wait longer for the evolutionary process to settle into equilibrium. In any case, my purpose for selecting a process is not the purpose of the process itself. All that the evolutionary process “does” is to settle into statistical equilibrium.

Sanity check of some claims in the book

Unfortunately, the most important thing to know about the Glass model is something that cannot be expressed in pictures: fitness has nothing to do with an objective specified independently of the evolutionary process. Which variants of traits contribute 1 to fitness, and which contribute 0, is irrelevant. The fact of the matter is that I ignore traits entirely in my implementation of the model, and keep track of 1s and 0s instead. Yet I have replicated Glass’s results. You cannot argue that I’ve informed the computer to search for a solution to a given problem when the solution simply does not exist within my program.

Let’s quickly test some assertions by Marks et al. (emphasis added by me) against the reality of the Glass model.

There have been numerous models proposed for Darwinian evolution. […] We show repeatedly that the proposed models all require inclusion of significant knowledge about the problem being solved. If a goal of a model is specified in advance, that’s not Darwinian evolution: it’s intelligent design. So ironically, these models of evolution purported to demonstrate Darwinian evolution necessitate an intelligent designer.

Chapter 1, “Introduction”

[T]he fundamentals of evolutionary models offered by Darwinists and those used by engineers and computer scientists are the same. There is always a teleological goal imposed by an omnipotent programmer, a fitness associated with the goal, a source of active information …, and stochastic updates.

Chapter 6, “Analysis of Some Biologically Motivated Evolutionary Models”

Evolution is often modeled by as [sic] a search process. Mutation, survival of the fittest and repopulation are the components of evolutionary search. Evolutionary search computer programs used by computer scientists for design are typically teleological — they have a goal in mind. This is a significant departure from the off-heard [sic] claim that Darwinian evolution has no goal in mind.

Chapter 3, “Design Search in Evolution and the Requirement of Intelligence”

My implementation of the Glass model tracks only fitnesses, not associated traits, so there cannot be a goal or problem specified independently of the evolutionary process.

Evolutionary models to date point strongly to the necessity of design. Indeed, all current models of evolution require information from an external designer in order to work. All current evolutionary models simply do not work without tapping into an external information source.

Preface to Introduction to Evolutionary Informatics

The sources of information in the fundamental Darwinian evolutionary model include (1) a large population of agents, (2) beneficial mutation, (3) survival of the fittest and (4) initialization.

Chapter 5, “Conservation of Information in Computer Search”

The enumerated items are attributes of an evolutionary process. Change the attributes, and you do not inform the process to search, but instead define a different process. Fitness is the probabilistic propensity of a type of organism to leave offspring, not search guidance coming from an “external information source.” The components of evolution in the Glass model are differential reproduction of individuals as a consequence of their differences in heritable traits, variety in the heritable traits of offspring resulting from recombination and mutation of parental traits, and a greater number of offspring than available resources permit to survive and reproduce. That, and nothing you will find in Introduction to Evolutionary Informatics, is a fundamental Darwinian account.

1,439 thoughts on “Evo-Info 3: Evolution is not search”

  1. Rumraket: Phoodoo seems to say no, do you agree with his assessment?

    I don’t think phoodoo is saying no. I think no one is listening to what phoodoo is saying.

    I definitely think that if you kill off the offspring you don’t want and keep the ones that you do want, selecting for a specific trait (long floppy ears maybe), that you can sometimes get things with long floppy ears.

    Why don’t all the seals take a page from the bears and turn white too? Why aren’t all arctic seals white? Why aren’t all arctic species white? Do whales live in white water? Why are there white whales?

    You have things that are white in a white environment. You have things that are not white in a white environment. You have things that are white in a non-white environment. Being white is adaptive unless it isn’t. Things that are not white, even in a white environment, are adapted too. They just aren’t adapted for whiteness.

    http://icestories.exploratorium.edu/dispatches/big-ideas/arctic-seals/index.html

  2. Mung: Wouldn’t it depend on whether the mutation was in the germ line?

    Yes, it would. Unfortunately there are plenty of those.

  3. Mung: I don’t think phoodoo is saying no. I think no one is listening to what phoodoo is saying.

    I think everyone is listening to what phoodoo is saying, and it’s not making sense. And I think you failed to answer my question once again.

    Why don’t all the seals take a page from the bears and turn white too? Why aren’t all arctic seals white? Why aren’t all arctic species white? Do whales live in white water? Why are there white whales?

    All of those are fine questions in their own right, but they don’t answer mine.

    Seals could have the colors they have for various reasons, not necessarily because of selection. There might not be any set of mutations that will cause them to be white, without requiring totally rewriting the underlying genetic structure that is involved in development of their skin, fur and the various pigments.

    But the seals don’t hunt seals or other arctic aquatic mammals, on the ice, like polar bears do, and they also spend a lot of time underwater chasing fish and so on.

    The premise of my question isn’t that it is impossible to make a living in the arctic without being white. The premise is that there is a good reason for a large, mostly land-based predator, to be white.

    What seems to be emerging from this discussion is that both you and phoodoo disagree, and that it is preposterous to imagine the polar bear being white is an advantage to it when hunting seals, walruses and so on. At least, both of you seem to be having a really hard time being clear on this point.

    Is the polar bear being white an advantage to it when it hunts in the actic? Does it lower the probability that it will be spotted prematurely while sneaking up on seals?

    The very fact that you don’t just come out with a clear answer is remarkable to me.

    You have things that are white in a white environment. You have things that are not white in a white environment. You have things that are white in a non-white environment. Being white is adaptive unless it isn’t. Things that are not white, even in a white environment, are adapted too. They just aren’t adapted for whiteness.

    Yes, there are many different ways to cope with some environment. Does that really mean we can’t say, or figure out, whether camouflage is an advantage in various situations?

    Forget biology. There are many different ways to cope with a battlefield. You can try to stay behind cover. You can overwhelm the enemy with numbers. You can use heavily armored equipment they don’t have the firepower to deal with. Or you can be hard to spot so you’re unlikely to get hit if shot at, or not get shot at at all because you’re not detected.

    Does the fact that a battlefield situation can be dealt with in many possible ways, mean we can’t say whether it is an avantage for someone on that battlefield to be camouflaged?
    I’m amazed because I’m inclined to belive you’d both answer yes to that question if we ask it in the context of evolution. And it seems so obvious to me that it can be an advantage, and when and where that might be.

    I suggest you spend 10 minutes on youtube looking at polar bears hunting seals. Often times the seals lie around on floating ice, looking nervously at their surroundings. The polar bears try to sneak as close to the seal as they possibly can, before jumping on them. They swim through a daylight-reflecting water surface, surrounded by big white ice floes and try to stay as low and silent as possible. Phoodoo insinuated earlier that he found it is implausible that seals don’t spot them immediately.

    Just look at this:
    Hungry polar bear surprises a seal – The Hunt: Episode 2 Preview – BBC One
    This one is particulary good because some numbers are mentioned. The polar bear at that time of year will fail 19 out of 20 attempts at catching a seal. Perhaps, just perhaps, being white is actually important at such a low level of success. Or not? Perhaps Joseph Felsenstein knows something about how little a help is needed for natural selection to matter in the long term.

    We could ask, if 1 in every 500 polar bears manages to catch an extra seal and therefore live long enough to have an extra seaon where it manages to leave offspring, would that be enough for the trait to fix in a population with an appreciable probability?

    Here’s another one with a sneaking polar bear:
    NINJA POLAR BEAR Vs SEAL!

  5. phoodoo,

    You mean there are probably more people with a unibrow than people with DMD, so they would be more fit?

    No. I mean the mean fitness of people with a unibrow is (in my assessment) almost certainly higher than the mean fitness of people with a debilitating genetic disease. It’s not to do with ‘how many there are’. Absorb this, repeat it nightly until you stop regurgitating it. When you start to type something that sounds like ‘how many there are’, imagine me on my your shoulder shaking my head with pursed lips.

    Allan Miller: An individual with both a unibrow and DMD would have its reproductive output added to both the ‘unibrow’ and the ‘DMD’ statistics.

    phoodoo: But I didn’t ask you about what the statistics are for DMD and what the statistics are for unibrows. I said, which counts more towards the fitness of an individual? They count equally? If DMD’s have less mean fitness, but unibrows have more mean fitness, what does that mean for the individual, do they cancel each other out?

    No, they don’t cancel each other out. The allele with the more significant selection coefficient (an exponent derived from the mean fitness) is the more likely to have an effect, in a given life. My bet is that would be the genetic disease.

    What do you think? Do you think that, in terms of affecting individual fitness:

    a) A debilitating genetic disease is exactly the same as any minor facial feature
    b) A debilitating genetic disease has more impact than a minor facial feature
    c) A debilitating genetic disease has less impact than a minor facial feature

  6. Rumraket: Seals could have the colors they have for various reasons, not necessarily because of selection.

    And by that very same logic, polar bears “could have the colors they have for various reasons, not necessarily because of selection.” Don’t you agree?

  7. Mung,

    It wasn’t dreamed up Allan, it actually happened to them. More than once. Read the freaking book.

    Calm down Mung. I am well aware that hurricanes happen. However, if you are trying to establish general evolutionary principles, hurricanes are probably not going to feature very bigly as issues for the average allele.

  8. Mung: And by that very same logic, polar bears “could have the colors they have for various reasons, not necessarily because of selection.” Don’t you agree?

    Yes, but DO they? Is it implausible? Does it make sense? Is there a way to find out?

    As I wrote: The premise of my question isn’t that it is impossible to make a living in the arctic without being white. The premise is that there is a good reason for a large, mostly land-based predator, to be white.

  9. phoodoo,

    Why hair colors, why eye colors, why are some dominant and some recessive. Why does a combination of genes affect a phenotype, what made it work out that way? Why are there mutations on the X chromosone but not on the Y? Why do some gene expressions skip generations? Why do mice remember bad things that happened to their ancestors?

    Saddling up the horse for a Gish Gallop. Some of those are questionable, but either way, are any relevant?

  10. Rumraket: Here’s another one with a sneaking polar bear:

    That’s pretty funny. The bear’s being white certainly didn’t catch the seal. Maybe more sneakiness would be more adaptive than more whiteness. If only the bear could trade some of its whiteness for more quickness.

    Just look at all those maladaptive traits. What kind of designer would design a polar bear with all those engineering flaws.

  11. Mung,

    Straw Man

    On the contrary, I have seen that very argument advanced, and I bet I’m not the only one.

    But rather than pursue that red herring soaked in oil of whatever you have thrown across my path, let us say: that fraction of mutations that hypothetical Creationist X accepts occurs and is deleterious. The number accepted by different Creationist X’s may be different, but they all have the common feature: that Creationist X expects those deleterious mutations to be eliminated. That would be Natural Selection, and hence an effect on fitness, would it not?

  12. Mung: That’s pretty funny. The bear’s being white certainly didn’t catch the seal.

    It didn’t catch the seal, but it still made it all the way to the ice floe before it was spotted. The idea that it’s whiteness generally has no helping hand in such endeavours is an idea that can only be seriously entertained by a lunatic.

  13. On polar bear colouration, we seem to have happened on a feature that a consistent Design enthusiast would now have to say was designed like that because it looks nice, rather than conferring any benefit to the designed product.

    Trying to deny selection has that effect on Design arguments.

    Of course, it’s possible that being white has no effect on fitness. We have this … by George, convergence! … on white colouration in numerous creatures that live in icy regions. Colouration that some lose in the summer, in seasonal latitudes. And it’s just – what? – drift?

  14. Allan Miller: that Creationist X expects those deleterious mutations to be eliminated. That would be Natural Selection, and hence an effect on fitness, would it not?

    By definition:

    deleterious mutation A mutation that lowers the fitness of its carriers.

    http://www.encyclopedia.com/science/dictionaries-thesauruses-pictures-and-press-releases/deleterious-mutation

    I don’t think you’d have any difficulty finding Creationists who attribute it to natural selection.

  15. Allan Miller: On polar bear colouration, we seem to have happened on a feature that a consistent Design enthusiast would now have to say was designed like that because it looks nice, rather than conferring any benefit to the designed product.

    Yep. 🙂

    Darwin did say that would be one way to falsify his theory.

  17. Mung,

    I don’t think you’d have any difficulty finding Creationists who attribute it to natural selection.

    I’m quite sure I wouldn’t. But we have one particular Creationist X who is doggedly proving the exception. It’s him I’m aiming at.

  19. We’re going to be here a long time putting up examples of beneficial features, for local Creationist representatives to deny any adaptive benefit, and hence, by extension, to deny that they represent Design-based optimisation either. They just look nice. To save time, can we state this as a general principle?

    “There is no Feature X which benefits its possessors.”

  20. Mung,

    By ‘looks nice’, I meant to the Designer, but hey ho. I dare say we like the look of ’em too, but that’s not why the Designer made them white. I have it on good authority.

  21. Allan Miller: By ‘looks nice’, I meant to the Designer, but hey ho. I dare say we like the look of ’em too, but that’s not why the Designer made them white. I have it on good authority.

    The foregoing remarks lead me to say a few words on the protest lately made by some naturalists, against the utilitarian doctrine that every detail of structure has been produced for the good of its possessor. They believe that very many structures have been created for beauty in the eyes of man, or for mere variety. This doctrine, if true, would be absolutely fatal to my theory.

  22. Mung: I don’t think you’d have any difficulty finding Creationists who attribute it to natural selection.

    Natural selection will never produce in a being anything injurious to itself, for natural selection acts solely by and for the good of each.

    Pretty obvious that humans weren’t brought about by natural selection.

  23. To sum up, I believe that species come to be tolerably well-defined objects, and do not at any one period present an inextricable chaos of varying and intermediate links: firstly, because new varieties are very slowly formed, for variation is a very slow process, and natural selection can do nothing until favourable variations chance to occur, and until a place in the natural polity of the country can be better filled by some modification of some one or more of its inhabitants.

    – Charles Darwin

    Natural selection can do nothing until favourable variations chance to occur. So I guess the deleterious mutations sort of hang around waiting for a favourable mutation so that natural selection can then do something about the deleterious mutations.

  24. Wow. Both phoodoo and Mung, by denying the selection of advantageous traits, have now sunk below the level of a typical creationist.

  25. When we see any structure highly perfected for any particular habit, as the wings of a bird for flight, we should bear in mind that animals displaying early transitional grades of the structure will seldom continue to exist to the present day, for they will have been supplanted by the very process of perfection through natural selection.
    – Charles Darwin

    Evolution as a process of perfection. One can forgive Joe, he was just echoing Darwin.

  26. Can’t forget this one:

    I can see no difficulty in a race of bears being rendered, by natural selection, more and more aquatic in their structure and habits, with larger and larger mouths, till a creature was produced as monstrous as a whale.

  28. More Darwin:

    He who believes in the struggle for existence and in the principle of natural selection, will acknowledge that every organic being is constantly endeavouring to increase in numbers; and that if any one being vary ever so little, either in habits or structure, and thus gain an advantage over some other inhabitant of the country, it will seize on the place of that inhabitant, however different it may be from its own place. Hence it will cause him no surprise that there should be geese and frigate-birds with webbed feet, either living on the dry land or most rarely alighting on the water; that there should be long-toed corncrakes living in meadows instead of in swamps; that there should be woodpeckers where not a tree grows; that there should be diving thrushes, and petrels with the habits of auks.

    So you see Rumraket, the color of the fur of the polar bear may have absolutely nothing to do with anything having to do with his current environment.

    Like web feet on dry land. etc.

  30. Mung: So you see Rumraket, the color of the fur of the polar bear may have absolutely nothing to do with anything having to do with his current environment.

    It might not, but it also might. What does reason tell us? What does evidence indicate?

    Mung, you’re going to have to do more than wave your hands in the direction of mere logical conceiveabilities.

  32. Joe Felsenstein: Particularly since that “Joe” was not me, but a quote-mine creation by Mung.

    Please explain why it was a “quote-mine creation,” beginning with why you wrote the words at all if you didn’t actually mean them.

    Mung quoting Joe: “The tendency of natural selection to increase mean relative fitness is simple enough to explain: the more fit genotypes are increasing in frequency, so that ultimately only the single most fit genotype will exist in the population.”

    – Joe Felsenstein

    Joe Felsenstein: Mung finds a quote from me, in my online text Theoretical Evolutionary Genetics, that has me mindlessly arguing that the most fit genotype always takes over the population. It’s from the section in Chapter II where I discuss fitness maximization.

    So you weren’t really being mindless, right? Were you also not really discussing fitness maximization? Because why would that topic even come up.

    Did you also not mean that there is a tendency of natural selection to increase mean relative fitness? Or do you mean that it’s not as “simple enough” to explain as you said. To echo Tom, where’s your model?

    Why are you trying to explain a tendency that is not there, Joe? If you’re going to accuse me of quote-mining, I think I deserve some answers.

    Joe Felsenstein: Yes, it did say that.

    Yeah. You said it. Which parts of it did you not mean?

    Joe Felsenstein: But it said more. It was from a discussion of what happens when we have a haploid locus (with constant relative fitnesses, in an infinitely large population). Or else an infinite population of clonally-reproducing genotypes. After the algebra, in which mean fitness always increases, I say that, and then start to talk about more complex cases.

    I think it said less. But let’s not quibble. It was from a chapter on Natural Selection and from a Section on Selection and Fitness and a sub section on Fitness Maximization. Which made it really easy for me to find just what I said I’d find. What on earth is that section doing in a book on population genetics?

    From your intro to the chapter:

    The third part concerns the effect of natural selection on the mean fitness of individuals in the population. It was a central tenet of Darwin’s thinking that natural selection had an average tendency to increase adaptedness, but it is a nontrivial matter to investigate whether or not it actually does so in simple model situations.

    From just prior to the text I originally quoted:

    Since the variance can never be negative, the mean relative fitness will never decrease as a result of natural selection. This is a fairly reassuring result. Natural selection seems to be doing what it is supposed to – make the organisms better adapted.

    Now Joe does point out that “in only one other, more complex case – multiple alleles in diploids – does mean relative fitness necessarily increase.”

    So Joe has just argued for two cases in which mean relative fitness necessarily increases. And I’m guilty of quote-mining for pointing this out. apparently there are cases in which it does not necessarily increase. But it may. Or may not.

    What we have are are cases of fitness maximization, and models for it, which I was told I could not find. Well, I did. Oops.

  33. Rumraket: Mung, you’re going to have to do more than wave your hands in the direction of mere logical conceiveabilities.

    😀

    Remind me again why there needs to be any reason at all for it under evolutionary theory?

  35. WHERE FITNESS IS MAXIMIZED – by Joe Felsenstein

    But then, alas, Gregor Mendel intervenes, the genes segregate, and the matter is cast in doubt. When we are not dealing with asexual clones, offspring are no longer of the same genotype as their parents. We cannot then use equation (II-109) to establish a net increase of fitness. It turns out that there the genetic system is not optimized to result in increase of fitness by natural selection. We would only expect such optimization of the genetic system if multiple genetic systems had competed, with choice among them according to their results. The system of inheritance that we have need only be good enough that there is a net increase if fitness most of the time. We are fit enough to sit here and read this book, but not we are not optimal organisms.

    Optimization. bark! bark!

    So we have one genetic system that is optimized to result in increase of fitness by natural selection. And we have one genetic system that is not optimized to result in increase of fitness by natural selection. And the reason that we have these two is that, for some mysterious reason, the two did not compete. And we know this because, if they had competed, we’d only have the one. I shit you not. Evolutionary thinking at its finest.

    But anyways, back to talking about fitness being maximized. Which just ain’t supposed to happen boys. Ever. Because evolution doesn’t maximize fitness. Except when it does.

  36. Joe Felsenstein: People can read my statements, including the Mung quote and the fuller passage from which it came, and judge for themselves what is going on.

    Of course. The quote-mine charge isn’t looking so good anymore. You win the keiths award* for the day. For the next 24 hours nothing you cay can possibly be wrong.

    * [keiths thinks he never has to justify his charges of quote-mining either.]

  37. I’m with Joe, actually. I encourage people to read as much as they can stand.

    Be sure to read the section on FITNESS OPTIMIZATION.

    We now have the pleasing picture of the population changing so as to continually increase ¯w, until it comes to rest at a peak of the adaptive surface. This would seem to provide a basis for the use of “fitness optimization” arguments in ecology and animal behavior. In those arguments it is assumed that the population will evolve to that collection of phenotypes which maximizes the mean fitness. The picture we have developed above is only partly consistent with this notion. In the first place, genetic constraints may prevent the population from achieving this optimum configuration. In a case of overdominance, the highest mean population fitness would be achieved if all individuals were to be heterozygotes. Mendelian segregation makes this impossible: a population of heterozygotes will not be stable – it will immediately segregate out some homozygous offspring. In the second place, the peak of mean fitness which is achieved need not be the highest available peak. When we have a case of underdominance, the final equilibrium achieved depends on the initial gene frequencies. Since the mean fitness at the equilibrium will be either 1−s or 1−t, depending on initial position, it is entirely possible that a population will fail to find the best solution to its adaptive problems. Although its fitness cannot decrease, it may be climbing the smaller of the two peaks of the adaptive surface. If it starts out at the smaller peak, it will never find its way to the higher peak if natural selection is the only force changing gene frequencies.

    I think I’ve died and gone to evolutionist heaven. Maximizing. Optimizing. Hill climbing. Problem solving. My throat is getting sore from all the barking.

  38. If it starts out at the smaller peak, it will never find its way to the higher peak if natural selection is the only force changing gene frequencies.

    But we can just imagine, that with just the right nudge, we can get over to that other hill and climb it all the way to perfection peak!

  39. SEGREGATIONAL LOAD. If the genetic system were asexual, reproducing by apomictic parthenogenesis, then natural selection would result in the increase to fixation of the most fit genotype. The failure of this to happen in outcrossing diploid populations is a weakness of the Mendelian genetic system.

    Natural selection would result in the increase to fixation of the most fit genotype. Can we persuade Tom to model that for us so that we can see it in action?

  42. It turns out that there the genetic system is not optimized to result in increase of fitness by natural selection.

    It’s not that it does not result in increase of fitness by natural selection, it’s that it is just not optimized for that. But it works well enough. 🙂

    So we’re still talking about maximizing fitness, either way. Maybe if we pretend there’s no problem here it will go away.

  43. keiths should be explaining why Joe’s words don’t mean what they clearly say rather than bitching about the moderators. That would be more in keeping with the rules and intent of the site and be more productive.

    Probably not going to happen though.

  44. Mung,

    Anyone who reads the passage can see that you quote-mined Joe. I’m not going to jump through hoops merely because you want to deny that.

  46. We know that a foolish consistency is the hobgoblin of little minds, at least according to Emerson. I wonder what he would have said about a foolish inconsistency?

  47. keiths: Joe didn’t say that!

    Joe F: Yes, I did say that.

    You’re just not credible keiths. Even more so when you cannot back up your claims.

    Tom English: The apologists of ID are really good at word games. But it’s hard to deflect pictures showing clearly that evolutionary processes settle into equilibrium, rather than seek out individuals of maximum fitness.

    Mung: Now in the same way that I can rather easily find evolutionists who present evolution as problem-solving, I am likewise sure that I can find evolutionists claiming that evolution maximizes fitness.

    And I did. Joe does both. And even mentions the fact that others do so as well. I backed up my claim. Unlike keiths.

  48. Rumraket: The idea that it’s whiteness generally has no helping hand in such endeavours is an idea that can only be seriously entertained by a lunatic.

    Maybe, but the idea that all the other bears that weren’t white starved to death, and that is why there are only white one’s left seems even more preposterous.

    You are not a lunatic, right?

  49. phoodoo,

    Maybe, but the idea that all the other bears that weren’t white starved to death, and that is why there are only white one’s left seems even more preposterous.

    That’s odd. I must.have missed where Rumraket made that claim. Could you provide a link, phoodoo?

  50. An aside: Has anyone else noticed how the misuse of apostrophes seems to correlate with creationism?

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