Noyau (2)

…the noyau, an animal society held together by mutual animosity rather than co-operation

Robert Ardrey, The Territorial Imperative.

[to work around page bug]

2,294 thoughts on “Noyau (2)

  1. Neil Rickert: But if you are talking about bees, it’s pretty hard to say what it is empirically. What’s the fitness of a sterile worker bee? It can’t be the number of offspring, unless the fitness is zero. But the fitness cannot be zero, because without worker bees the whole hive collapses.

    A sterile worker contributes to the extended phenotype. Her copy of the hive genotype dies with her but she contributes to the survival of the genotype that passes down the germ line of mated queens.

    Why am I getting a feeling of déjà-vu?

  2. Alan Fox: Sickle cell disease happens when you have two copies of the sickle cell allele. If you only have one copy it is asymptomatic. What heterozygous carriers get is some protection from malaria.

    Correct. Salvador is ignoring the dominance effect. I believe there is some mild anemia in heterozygotes though.

    Alan Fox: So if the environment had no prevalence of malaria, the sickle cell allele in heterzygous form is neutral and would probably disappear through drift.

    Yes, it will first decrease due to its deleterious effect in homozygotes, and then either disappear or settle into mutation-selection equilibrium

    Alan Fox: But in areas where malaria was rife, heterzygous carriers benefited from the resistance to malaria, the allele was positively selected, which is why the sickle cell allele is present at higher levels in populations exposed to malaria. The environment is the crucial selecting factor.

    And now for the cool part: there is a point at which the sickle-cell allele WILL NOT rise any more in frequency, because the deleterious effect in homozygotes will start outweighing its benefit in heterozygotes. Natural selection is actively preserving BOTH alleles.

    So which allele confers the highest fitness? 🙂

  3. Allan Miller: A curious world we visit, though, where phoodoo insists an allele can neither increase nor decrease in a population – nor, I guess, stay the same – contingent upon any effect it has upon the fate of its bearers.

    He seems to accept that traits can increase and decrease. For example, it would appear that being skinny is advantageous in keeping starving people alive, wouldn’t you agree?

  4. Corneel: there is a point at which the sickle-cell allele WILL NOT rise any more in frequency, because the deleterious effect in homozygotes will start outweighing its benefit in heterozygotes. Natural selection is actively preserving BOTH alleles.

    Yes, exactly!

  5. Corneel: I don’t think there exists a definition that is appropriate to each and every situation that gets thrown around here. There is a good reason multiple definitions are in use.

    🙂

    I think Allan even wrote that his only applied to asexual organisms.

  6. Alan Fox: Alleles almost surely do not enjoy constant fitness through time. Instead the fitness, either absolute or relative, of most alleles likely fluctuates through time in response to physical and biological changes in the environment.

    Random physical and biological changes in the environment. Making natural selection itself in essence random.

  7. Allan Miller: The purpose of fitness in population genetics is to provide some quantification or analytic tool that represents natural selection

    Precisely. And that does not apply only to population genetics. I found Stephen Stearns saying something similar in my copy of “The Evolution of Life Histories” :

    All fitness definitions are tools invented by scientists to analyse natural selection. They should be judged by how well they do a particular job and replaced if necessary.

  8. Mung: So you believe in multiple designers.

    Well, that’s, in my view, a “why” question that science doesn’t attempt to answer. It does give an opportunity for theists to claim God”s mechanism for designing the Universe and hence the environments we inhabit.

  9. walto: My own sense is that it can be given a nice def that will work everywhere.

    It can be, but that definition is tautological. Some people see that as a problem others do not.

    If you want to make the definition testable, then you need to come up with a special definition of fitness that is not tautological. Thus the many and varied definitions of fitness.

  10. When you say the definition is tautologous, I take it you mean that everything will be fit just in case it is fit. I don’t see why a definition that could be used all throughout evolution studies would have to have that defect. I admit again, though, that I’m not really the guy for this job.

  11. However, fitness is hard to define rigorously and even more difficult to measure….An examination of fitness and its robustness alone would thus not yield much insight into the opening questions. Instead, it is necessary to analyze, on all levels of organization, the systems that constitute an organism, and that sustain its life. I define such systems loosely as assemblies of parts that carry out well-defined biological functions.

    Andreas Wagner

  12. Dennett is fond of speaking of selection as leading organisms through “Design Space”: Selection “lifts” organisms along “ramps” of good Design. The first is that natural selection cares about Design. In reality, selection “sees” only brute birth, death, and reproduction, and knows nothing of Design. Selection — sheer, cold demographics — is just as happy to lay waste to the kind of Design we associate with engineering as to build it. Consider the eyes of cave organisms who live in total darkness. If eyes are expensive to make, selection can wreck their exquisite engineering just as surely as it built it. An optic nerve with little or no eye is most assuredly not the sort of design one expects on an engineer’s blueprint, but we find it in Gammarus minus. Whether or not this kind of evolution is common, it betrays the fundamental error in thinking of selection as trading in the currency of Design.

    Second, hazy imagery of selection lifting organisms along Design ramps makes it hard to see that selection sometimes moves individual traits down ramps. But this surely occurs.

    Alllen Orr

  13. Unfortunately the determination of fitness is a great deal more complicated than is usually supposed. It is easy to say that fitness of a type is its “relative probability of survival and reproduction” but turning that phrase into a coherent measure that can do work in evolutionary explanation is not so easy.

    First, it is obvious that the fitness of a type depends on the environment in which the organism lives. But the environment is not independent of the organism. Organisms, by their biology, determine what aspects of the external world are relevant to them and constantly change their environment by their life activities. That means that as a collection of organisms evolves, their environment evolves with them.
    ….
    The problem is that it is not entirely clear what fitness is. Darwin took the metaphorical sense of fitness literally. The natural properties of different types resulted in their differential “fit” into the environment in which they lived. The better the fit to the environment the more likely they were to survive and the greater their rate of reproduction. This differential rate of reproduction would then result in a change of abundance of the different types.

    In modern evolutionary theory, however, “fitness” is no longer a characterization of the relation of the organism to the environment that leads to reproductive consequences, but is meant to be a quantitative expression of the differential reproductive schedules themselves. Darwin’s sense of fit has been completely bypassed.

    How, then, are we to assign relative fitnesses of types based solely on their properties of reproduction? But if we cannot do that, what does it mean to say that a type with one set of natural properties is more reproductively fit than another? This problem has led some theorists to equate fitness with outcome. If a type increases in a population then it is, by
    definition, more fit. But this suffers from two difficulties. First, it does not distinguish random changes in frequencies in finite populations from changes that are a consequence of different biological properties. Finally, it destroys any use of differential fitness as an explanation of change. It simply affirms that types change in frequency. But we already knew that.

    Richard Lewontin

  14. Allan Miller: Fitness is context dependent, of course it is. That doesn’t make it worthless as a concept or without power to effect any change of frequency.

    Fitness is not context dependent unless you’re equivocating over the term. You seem to be saying that the concept of fitness is context dependent. Also, fitness has no power to effect change.

    Entropy: Taking a concept out of its context doesn’t mean that the concept is wrong. It just means that you’re equivocating.

    Yup. As soon as you take fitness out of the context of the mathematical framework in which it is defined it doesn’t mean that the concept is wrong, it just means that you’re equivocating.

  15. What does Wagner suggest instead of “fitness”?

    it is necessary to analyze, on all levels of organization, the systems that constitute an organism, and that sustain its life. I define such systems loosely as assemblies of parts that carry out well-defined biological functions.

    Which sounds a lot like Michael Behe!

    A single system composed of several well-matched, interacting parts that contribute to the basic function of the system

    These we define many of these functional systems in biology. Such as a metabolic system.

    Krebs won the Nobel Prize for figuring this system (below) out. He spent a lot of his life working to see the architecture God put together at the molecular level.

  16. stcordova: [Sal quoting Richard Lewontin] First, it is obvious that the fitness of a type depends on the environment in which the organism lives. But the environment is not independent of the organism. Organisms, by their biology, determine what aspects of the external world are relevant to them and constantly change their environment by their life activities. That means that as a collection of organisms evolves, their environment evolves with them.

    Not sure why you quote this, Sal. Seems perfectly reasonable, especially WRT Homo sapiens.

  17. Mung: Fitness is not context dependent unless you’re equivocating over the term. You seem to be saying that the concept of fitness is context dependent.

    Semantics, semantics. Don’t you think that Allan meant that the genotypic fitness values were context dependent?

    Mung: Also, fitness has no power to effect change.

    But fitness variation does, right?

  18. stcordova: Thus it is equivocatable.

    Which is why you should not forget the damn context Sal. How many times should I repeat this until you get it?

    Many words are defined differently in different contexts. Sure, that means people can be mistaken, but tell them the context and they’ll get it. You seem determined to care little, if at all, of the context just to make the concept of fitness into a problem. You’re equivocating in spite of all these explanations. What makes you think that people who understand context will take your equivocations as a problem for evolutionary theory, rather than as a problem with your understanding?

  19. Entropy,

    You seem determined to care little, if at all, of the context just to make the concept of fitness into a problem.

    How do you think the concept of fitness adds value to understanding biological diversity?

  20. I find it amusing that some are arguing that its perfectly fine to have two definitions, one for math and one for the real world.

    What exactly is the point of the math? For fun?

  21. colewd:
    Entropy,

    How do you think the concept of fitness adds value to understanding biological diversity?

    Its like playing sudoku, it gives you something to do.

    Who cares if its empirical.

  22. colewd: How do you think the concept of fitness adds value to understanding biological diversity?

    It explains how adaptations spread in populations.

  23. phoodoo:
    I find it amusing that some are arguing that its perfectly fine to have two definitions, one for math and one for the real world.
    What exactly is the point of the math?For fun?

    Your illiteracy on display once again. You confessed that you don’t read, and before you’ve demonstrated that you’re illiterate. So there’s no point in explaining this more to you.

  24. Corneel: Semantics, semantics. Don’t you think that Allan meant that the genotypic fitness values were context dependent?

    I tried to make it evident that I considered that explanation and rejected it.

    I provided a fuller quote than I really needed to in order to establish that he was in fact speaking of the concept of fitness rather than the value.

    That doesn’t make it worthless as a concept

    But I’m willing to hear what he has to say.

  25. Corneel:
    Mung: Also, fitness has no power to effect change.

    But fitness variation does, right?

    Neither fitness as a concept nor fitness as a value. Changes in fitness as a value are effects not causes.

  26. phoodoo: What exactly is the point of the math? For fun?

    It provides a flavor of scientific respectability. Any truly physical theory needs mathematics to back it up.

    ETA: It’s known as “physics envy.”

  27. Mung: I tried to make it evident that I considered that explanation and rejected it.

    I provided a fuller quote than I really needed to in order to establish that he was in fact speaking of the concept of fitness rather than the value.

    That doesn’t make it worthless as a concept

    But I’m willing to hear what he has to say.

    I think people are making a mess by using the word “context” to mean both the framework in which the concept is defined, and the environment.

    I think I might have made this mistake myself in one of my long explanations to Salvador, but no worth in checking, since Salvador is determined to equivocate either way.

  28. Mung:
    There seems to be a lot of agreement in this thread. 🙂

    More than I’ve expressed. Maybe we should insult each other to make sure it’s us.

  29. keiths: If the teacher is more capable and knowledgeable than the student, then the student has more reason to be humble than the teacher.

    You don’t say why, you simply repeated yourself. I gave a reason why the teacher ought to be more humble.

    In addition to what I’ve said previously, any teacher who fails to acknowledge that her capability is a gift is ignorant and unworthy. Any teacher who fails to acknowledge that her knowledge came from others is ignorant and unworthy.

  30. The Oxford Handbook of Probability and Philosophy

    See Part VI. Chapter 28.

    I examine the concept of “fitness” in the philosophy of evolutionary biology to show how discussions of probability in biology can go wrong, and right. Many of the critiques of the propensity interpretation of fitness have focused on the mathematical aspects of fitness; re-focusing on several aspects of the propensity interpretation of probability more generally can help to address these concerns. I conclude with some general lessons for thinking about probability in biology. The propensity interpretation of fitness, properly understood, solves the explanatory circularity problem and the mismatch problem, and also withstands many other problems. Fitness is the propensity for organisms to survive and reproduce in particular environments and in particular populations. Fitness values can be described in terms of distributions of propensities and can be modeled for any number of generations using computer simulations. Fitness is a causal concept. Relative fitness is what matters for natural selection.

  31. : The Oxford Handbook of Probability and Philosophy
    : Chapter 28.4.1 Non-mathematical Fitness or Mathematical Fitness?

    How should we sort through these widely varying reactions to what Sober (2001) has dubbed “the two faces of fitness”?

  32. We have juvenile diabetes and cancer in mammals. Why didn’t selection remove it? Well, maybe it added reproductive “fitness” to the population. That is the thesis of Moelem’s book, Survival of the Sickest, why we need disease.

  33. phoodoo:
    stcordova,
    Is there anything selection can’t explain!

    Of course not! We define Natural Selection as “The All-Powerful God That Can Explain Everything!” And we write everything referring to It, like pronouns standing for It, with capitals when nobody is watching.

    Ups! Did I write that in public?

Leave a Reply