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Survival of the Rarest?

Researchers have discovered that in certain competitive situations, the “fittest” phenotype is the one that is “rarest” for a given population. In a study of fruit flies, when “rovers” and “sitters” were foraging together, “rovers” did better if they were surrounded by “sitters”, and vice versa. As the author of the study put it: “If you’re a rover surrounded by many sitters, then the sitters are going to use up that patch and you’re going to do better by moving out into a new patch. So you’ll have an advantage because you’re not competing with the sitters who stay close to the initial resource. On the other hand, if you’re a sitter and you’re mostly with rovers, the rovers are going to move out and you’ll be left on the patch to feed without competition.”

She also said: “There’s considerable genetic variation in nature and we haven’t been able to explain why it persists, since natural selection ensures that only the best survive.” So, which is the best, the “rover” or the “sitter”? Well, as Mark Fitzpatrick, a doctoral student involved in the study, states: “In the case of fruit flies, one variant encourages the survival of the other. In essence, there is not one best type of fly.”

I know there are population geneticists out there, so, if you can, how would you explain NS being able to virtually decide that it is “best” to conserve both forms, rather than to single out one of the two forms? Or, does this mean that there really is no such thing as “fixation” and “extinction”, thus rendering neo-Darwinism null and void?

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33 Responses to Survival of the Rarest?

  1. PaV – I’m afraid your questions show that you haven’t understood evolution. It’s basic that evolution isn’t teleological, so it doesn’t “decide” that it is best to conserve diversity. It’s just that, in this case, the population will evolve to a state with more than one phenotype. So your question is moot.

    What’s being described is called frequency dependent selection, and is well known in population genetics. It’s also not universal: there are some traits that are under frequency dependent selection (the sex ratio is one), but not all traits (and probably only a minority). Hence, your second question is also moot.

    Bob

  2. Actually, it’s not basic that evolution isn’t teleological – it’s basic that any question of teleology with regards to the natural world is a philosophical question (Unless, of course, ID scientists are correct). Declaring it (or parts of it) to be obviously devoid of teleology would be tantamount to saying you have a mechanism for discerning design, which.. well, connect the dots.

  3. Bob: “PaV – I’m afraid your questions show that you haven’t understood evolution. It’s basic that evolution isn’t teleological, so it doesn’t “decide” that it is best to conserve diversity.”

    You’ll notice that I wrote “virtually decide”. Nonetheless, what we see is the appearance of some “decision” on the part of NS in this case since standard theory would say that either form A, or form B—either the “rover” or the “sitter”—is the fittest, and then choose for one or the other, while here NS seems comfortable with two forms. So NS seems to have “decided” that in this case, it’s not going to follow standard procedures. You’ve given this phenomena a name, and in the article they call it “negative frequency-dependent selection”. But giving something a name doesn’t mean you’ve explained the phenomena; nor does it mean that the phenomena fits into standard population genetics. Again, I would appreciate some attempt at explaining why we find this phenomena in nature. Can you supply it?

  4. This phenomena isn’t that hard to understand if you think about how the population can change over time. For example, imagine a situation in which the “rovers” are more common. Since the “sitters” will start to be more successful and therefore more populous.
    Over time, as the sitters gain population, there will be a turning point at which this strategy will no longer be as big an advantage as it once was.
    The rovers that remain (since they aren’t all going to go away suddenly) will then start to get a slight advantage as they are outnumbered by the sitters. This may take some time, as the effects may take generations to play out.

    My understanding is that this will continue is a see-saw pattern indefinitely. I assume that this could be modeled in a similar fashion as other dynamic equilibrium systems, such as deer/wolf population models, etc.

  5. “Again, I would appreciate some attempt at explaining why we find this phenomena in nature. Can you supply it?” –PaV

    What needs to be explained? You already explained it in the original article! NS does not say anything about “final” outcomes and it doesn’t care who “wins”. NS is about the fittest surviving within a particular situation. And it’s about probability:

    When there are more sitters, the rovers are more likely to thrive and vice versa. You even explained WHY this happens in the original post.

    “Survival of the Rarest” as you put it is quite common actually, since being “rare” often means you have less competition.

    NS doesn’t say any species has to totally win or lose, just that in a specific situation (time and place) the fittest will survive. And that’s exactly what’s happening here.

    Your understanding of NS seems to imply that eventually there would be only one life form in the whole world. :P

  6. Eric: “This phenomena isn’t that hard to understand if you think about how the population can change over time.”

    Yes, I agree, if you choose to look at the population switching from one form to another as environmental conditions change over time, then this makes perfect sense. But, wait a minute, what about the coloration of Bison bistulleria? What about the beak sizes of the finches in the Galapagos Islands? Isn’t it true that over time one trait is more advantageous than another? So, then, how does one define the “fittest”? And if there isn’t just one definition for the “fittest”, then how can evolution—the “survival of the fittest”, supposedly—make a choice? And, if it is then protested that in only certain situations this proves to be the case, then this only further obscures the equivocation that is Darwinism: Who survives? The “fittest”. Who are the “fittest”? Those who survive. Now we can add: Who survives? The “rarest”. Who are the “rarest”? Well, that all depends…..

    As I initially stated, NS is virtually making a choice to “balance” these two forms. And we can see the reason why this is “good”, but we have foresight, and NS, as someone already posted, has none—it’s non-teleological, it can’t see purpose. So why does NS balance forms here, but not in the case of rhinoceroses?

    Or, to put it another way, if only the “rovers” existed, would anybody be saying, “Oh, there ought to be a “sitter” population to balance them off”? I seriously don’t think so. Then how does NS ‘blindly’ come up with this ‘choice’?

    And let’s remember that this group wouldn’t be studying this in the laboratory if it didn’t bother them from a theoretical standpoint. This situation represents a breakdown in the theory: there isn’t any one form that corresponds to the “fittest”. If that’s always the case, then how could evolution have ever taken place? Or, to contextualize, in the fossil record you see animal forms coming directly (no intemediates) into existence, varying over time (oscillating between forms), and then becoming extinct. Is NS no better than a force that keeps species moving between different forms of the same species? If so, then NS is no more than a stabalizing, adaptive process, and should be more properly called “adaptation”, and not “microevolution”—since nothing truly evolves, but rather, there is only a change in forms that is brought about by a stochastic process that involves an interplay between the information within the genome and the environment.

  7. PaV, we had a similar discussion a while back in dealing with NS and how it is defined. In the course of the discussion I became convinced that there is no non-circular, generally applicable definition for fitness. What convinced me was the very density-dependent effects you speak of.

    If the definition of fitness is generally applicable, it is circular. If non-circular (i.e. specific traits for specific enviornmental contraints) then it isn’t generally applicable (and sometimes not even consistent).

    In the end we have survival of the survivors and it is hard to get more specific.

  8. I don’t understand what you people are arguing. Do you want to say that something OTHER than the fittest survive?

    “Survival of the fittest” is circular. It’s also an over-simplification and worded as such to make it easier to understand. It’s also obviously true.

    Try “heritable variations lead to differential reproductive success” which is what Darwin originally said.

  9. Thank you superjer.

    Which organisms survive? Those whose “heritable variations lead to differential reproductive success”.

    What exactly are those “heritable variations [that] lead to differential reproductive success” (which variations, in other words)? Those of the dominantly surviving organisms.

    I’m not saying it isn’t true; I just happen to think it is a somewhat useless concept due to its circularity or non-generality.

  10. It seems like some of the confusion lies in the sound-bite of “survival of the fittest.” You seem to be extrapolating from it to say things that don’t necessarily follow.
    The main oversimplification here is the implication that the forms that are not the fittest completely cease to exist – which may not always be the case. The fittest is the *most likely* to pass on traits, but not the only one.
    The inappropriate extrapolation is that there is only one way to be the fittest in a group. In fact, there may be many strategies to be successful. For example, maybe a rover in a group of sitters, or the fly with the longest proboscis or the one that has the best eyesight (to avoid predators) or the one with the best resistance to poison. Each of these will be successful in some way and pass on it’s genes. If you followed the “family tree” for one of these, you may not learn much, but over the course of the entire population, those little differences start to add up to major changes.

    So, to address this quote:
    “Or, to put it another way, if only the “rovers” existed, would anybody be saying, “Oh, there ought to be a “sitter” population to balance them off”? I seriously don’t think so. Then how does NS ‘blindly’ come up with this ‘choice’?”
    The sitters were already there… passing on genes, but not as often as the rovers, so their numbers were smaller. As the ratio changes that strategy becomes more advantageous and they start to become more successful. No “decision” had to be made to introduce this behavior.

    The fact that there are two traits that balance each other out this way is probably not unique in nature, but it isn’t the only way. If some adaptation doesn’t have something to balance it out, it may become the dominate trait with no seesaw.

  11. From the post:
    “…how would you explain NS being able to virtually decide that it is “best” to conserve both forms, rather than to single out one of the two forms?”

    Though I am not a population geneticist, I think your answer is that Nature doesn’t “select” or “decide”, virtually or otherise: organisms self-select, since the very act of differentially reproducing is what the “selection event” consists of.

    Therefore, if an organism can’t self-select more than its competitor, and vice versa, we get a tie. Neither happens to be the “fittest”, they’re equally successful.

  12. eric

    Survival of the fittest isn’t the best term I’ve seen but it’s one Darwin heartily endorsed in the 5th revision of The Origin as being superior in some ways to Darwin’s original phrase Natural Selection. The best term IMO is differential reproduction.

  13. Speaking of flies

    Why do fruit flies get all the glory? ;-)

    What about blue bottles? Dear flies? Horse flies, black flies, blow flies, syrphid flies, cleg flies, noon flies, the infamous Tsetse flies, dung flies etc….? There are around 120,000 species of flies in the world.

    It is estimated that houseflies carry around 1,941,000 different kinds of bacteria. Nice to have around the picnic table huh.

    Flies are way tougher than jet fighters, much more flight capable and equipped with way better menace avoidance mechanisms – not to mention they can land upside down :-o

    A whole family of flies the Cyrtidae (about 250 species) are all internal parasites of spiders during their larval life. The eggs are laid on the ground and the first instar larva wait on damp vegetation for a passing spider. They leap up and attach themselves to the spiders body where they slowly eat their way through its cuticle before eating the spider from the inside out.

    Can ya say symbiotic? (Another thing Darwinism fails to account for)

    The dance fly is a species of the genus Empis. Males catch an insect as nuptial gift for the female. In the mating swarms the partner is selected, the gift is transferred and the couple leave the swarm.

    Usually the females select smaller flies carrying smaller ‘gifts’ rather than larger stronger ones.

    In fact those little beggars actually ‘steal’ food from spiders webs!

    Wonder where they learned that stuff? Oh, sorry Darwinism explains it right? Not a chance.

    Yeah, flies – they’re all very fit.

    Complexity? Yes. Astounding complexity – flies have among the most sophisticated flight systems around. And very smart behavior don’t ya think for a bug that has a brain smaller than a grain of sand?

    Darwinists traditionally try to explain the evolution of things like this by making gigantic leaps over 1000′s of complex, compounded mutational/selectional steps in a single just-so story that presumes – without any evidence whatsoever – that the pathway was just that simple. Gross oversimplifications are the norm. Just read Dawkins!

    Darwinism fails to explain the existence of flies as much as anything else. RM+NS is not a magic wand creating millions of awe inspiring, very well adapted bugs at random.

  14. superjer

    heritable variations lead to differential reproductive success

    Far more often it leads to reproductive failure. Natural selection is a conservative force. It kills those with deleterious mutations with much greater rapidity and force than the rare individuals with beneficial mutations are rewarded.

    In any case it still boils down to “reproduction of the reproducers” and that’s still a tautology.

  15. Eric: “The main oversimplification here is the implication that the forms that are not the fittest completely cease to exist – which may not always be the case. The fittest is the *most likely* to pass on traits, but not the only one.”

    But if this is conceded, then what becomes of the notions of “fixation” and “extinction”, as I originally posted? If you can’t get rid of the “old” (the “unfit”), or get the “new” (the “fit”) to surpass some large fraction of the population, then how does anything “new” come about? How can “evolution”—the progressive kind—happen? NS—which is likely not really any kind of selection at all but simply a stochastic process involving the genome and changing environment—seems to do no more than act as a conservative force that maintains organisms within various ranges of phenotypic expression.

  16. PaV,

    Good find. It is possible the explanation is density dependent selection, however, that can’t always be resorted to as an explanation.

    Furthermore, frequency-dependent seleciton would tend to resist Darwinian phyletic transformation and origin of new species since there is no extinction of diversity. :-) Catch-22.

    The other interpretation is that Natural Selection is not much in operation. It’s the wrong paradigm to describe what is going on.

    Take for example the related issues of molecular evolution. Kimura, Jukes, King, Ohta….. many others showed Natural Selection is the inappropriate paradigm to describe molecular evolution.

    It stands to reason that if the overwheling majority of molecular evolution is not governed by Natural Selection, probably lots of other things are NOT governed by natural selection as well!!!

    At some point, Natural Selection is hard to justify even as an operational science for many things in the wild:

    The Strength of Natural Selection in the Wild by Berlinski.

    Thus if a change in the length of a beak’s finch by one standard deviation explains 16 percent of the change in the population’s fitness, 84 percent of the change is not explained by selection at all.

    These results, although at odds with those reported by Endler, are not in themselves astounding. It is when sample sizes pass beyond samples of 1000 that results become far more difficult to accommodate, for under these circumstances, Kingsolver reported, both linear and quadratic selection were virtually non-existent.

    Most arguments for natural selection involve extreme examples like anti-biotic resistance and pesticide resistance. However, in such cases we’re dealing often with a few molecular “traits”. There are many molecules and possiblly other “traits” that must necessarily escape Natural Selection. There are simply insufficient population resources to police billions of molecules…

    Haldane’s cost of natural selection keeps rearing it’s ugly head!!!

    From the article:

    There’s considerable genetic variation in nature and we haven’t been able to explain why it persists

    It is true that density-related selection can give rise to balanced polymorphisms (for lack of better term I use polymorphism not only for proteins but for other traits), but that is not necessarily the explanation for every diversity of traits, nor even the majority of diversity!!!

    This echoes something the non-Darwinist-neutralists like Kimura had to wrestle with:

    Kimura challenged the idea that protein polymorphisms were maintained by some form of balancing [desity dependent]selection and argued, instead, that the alternative alleles were adaptively neutral.

    Merrell
    Ecological Genetics,
    p 319

    Whoa! Selection has nothing to do with diversity in protein diversity. It’s not hard to see this argument could extend beyond protein polymorphisms to almost anything else.

    Kimura challenged the idea that protein polymorphisms were maintained by some form of balancing selection and argued, instead, that the alternative alleles were adaptively neutral.


    The neutralist theory appears to have been proposed because the amount of protein polymorphism observed seemed too great to be maintained by selection.

    Merrell
    p 320

    I have predicted the problems which excorcised Darwinism form molecular evolution will excorcise Darwinism from other forms of evolution. Nature is telling us that Natural Selection is not the major cause of biotic reality.

    By the way, let’s assume frequency-dependent selection is at work in this case. How hard is it to create populations with such a beautiful feedback mechanism like frequency-dependent selection? There is almost a symbiosis here to preserve diversity!

    So there Darwinism is challenged on 2 counts:

    1. if it is density-dependent selection, this sort of selection is not really Darwinian (as in the origin of new species, or phyletically transforming a population).

    2. if selection is not at play, then Darwinism can’t be the explanation

  17. Pav

    seems to do no more than act as a conservative force that maintains organisms within various ranges of phenotypic expression

    I believe that’s essentially what Italian geneticist Giuseppe Sermonti wrote in the book “Why is a Fly not a Horse?”. He maintains that natural selection conserves the essential character of species within certain bounds and kills any that (I think these are his words and if not they might be my paraphrase) “wander too far off the reservation”.

  18. Isn’t it true that over time one trait is more advantageous than another?

    There is no necessity for this to be so. One thing that is often stressed is that fitness is only relevant to the environment: change the environment, and fitness changes.

    What happens in frequency dependent selection is that the fitness depends on the frequency of the phenotypes, so when as the frequencies change over time, due to selection, so do the fitnesses.

    The end result would probably be a that both phenotypes would be in the population at stable frequencies. The frequencies will be at the point where the slope of the fitness surface is zero.

    Your worries about fixation are unwarranted. Frequency dependent selection does happen, but it’s not universal. So, just because this phenotype doesn’t become monomorphic, it doesn’t mean that no trait can become fixed.

    Bob

  19. Bob O’H: “Your worries about fixation are unwarranted. Frequency dependent selection does happen, but it’s not universal. So, just because this phenotype doesn’t become monomorphic, it doesn’t mean that no trait can become fixed.”

    The problem I have here, and that I’m trying to point out, is that it is as though NS can have it two ways: it can either choose one form over another (let’s say this is its preferred method), or it can allow more than one form to exist, as here (a more rare performance by NS). Well, then, how does NS “decide” when to choose only one form, and when to leave more than one form? How does it “know” to do this? If one accepts that NS can do both, this is then like NS “eating its cake, and having it, too.”

    DaveScot: “I believe that’s essentially what Italian geneticist Giuseppe Sermonti wrote in the book “Why is a Fly not a Horse?”.”

    I’ve read Hoyle’s “Mathematics of Evolution” for the third time now. He essentially says that NS is only able to accomodate changes of one or two nucleotide changes at most. So he sees this as confirmation of microevolution—which, again, I prefer to think of as simply “adaptation”. So NS becomes an “adaptive” force, and not a “creative” force. (BTW, from many of the things you’ve written, I’d say you’re probably familiar with Hoyle—or else, you’ve reached many of the same conclusions in your own manner. Are you familiar with Hoyle’s ideas about “genetic storms”?)

  20. I have a question. Are not these two fruit flies, different species that don’t inter breed? If so then then Natural Selection is not the issue but we should look at ecological issues of resource sharing. They are using common resources and their behaviors will determine where they locate.

    So I do not see why natural selection is an issue which is the selection of different alleles within the same population. And this appears to be two separate populations.

  21. I have not read Hoyle, so forgive me for glossing over any reference to that, but I can speak to you question: “Well, then, how does NS “decide” when to choose only one form, and when to leave more than one form?” in a purely mathematical way.

    Chaos theory teaches us that iterative functions can produce many complex behaviors from simple forms with only small changes input. The Mandlebrot set is probably the most famous of these, but there are actually simpler examples. There are a large number of starting values that decay to zero and then, in a seemingly unpredictable pattern, there is a cusp at which the values diverge to infinity. In this way, a simple function has two very different results – given only slight changes in input.

    Now, apply this to the concept of NS. Model it as an iterative equation with many inputs (the iterations are each successive generation, the inputs are the traits of the animal and the environmental forces acting upon them). Obviously, a function that modeled it perfectly would be difficult, there are too many variables, but conceptually it could get close. The “results” over many iterations of this function may manifest in different ways. It could decay to a single result (representing a single form being successful) or it could oscillate between two or more forms that all have advantages that keep them competitive in the current environment.

    Keep in mind, of course, that (as Bob O’H pointed out) the environment changes. These environmental changes are what “keeps things moving” and evolving. Two populations that are separated may undergo different changes because of adaptations to the current environment they are in.

    Frankly, I don’t understand why this is a sticking point here. A few comments have presented false dichotomies – arbitrarily claiming that NS needs to operate in one or the other method. I don’t see why this is necessary – partly due to what I have seen in chaos theory and how well it models what we see in nature.

  22. We tend to argue over natural selection a lot here and it is really a very simple concept that the general public finds easy to understand. They witness in their daily life and so do we. The discussion about natural selection should not be that it doesn’t work or why it works but that it only produces trivial results when in fact it does work. It is a ho-hum of a concept, probably the most over hyped true concept in the history of science.

    The only reason why people still spend much time talking about it is because Darwin said it was the basis for his theory. Most population geneticists give it lip service and have put it on the back burner a long time ago and we should follow their example. We just give it more credence by arguing about it and should take the tact that it is trivial rather than if it worked or did not in a particular instance.

  23. On the contrary, natural selection is the only “mechanism” availabe to explain “the appearance of design” and thus is central to the debate.

    Also keep in mind that fluctuations increase the cost and/or slow the rate of evolution.

    But then, it seem to me that as one poster has insightfully pointed out, that we may be dealing with traits which are already fixed, and two completely separate populations. But then again, probably not. Would the authors of the article have made such a fundamental error?

  24. jerry, “The only reason why people still spend much time talking about it is because Darwin said it was the basis for his theory.”

    Tell that to Dawkins, Eugenie Scott, and the rest of the barking dogs, esp those who control the public education system and universities.

    We talk about RM+NS a lot because that’s the chief hammer in the materialist toolbelt.

  25. mike1962,

    What’s wrong with RM + NS? It is good science. Mutations happen and natural selection happens. Both are well documented. It looks foolish criticizing such an obviously true process as natural selection.

    Criticism should be directed to what natural selection has to work with not the process itself.

  26. The problem I have here, and that I’m trying to point out, is that it is as though NS can have it two ways: it can either choose one form over another (let’s say this is its preferred method), or it can allow more than one form to exist, as here (a more rare performance by NS). Well, then, how does NS “decide” when to choose only one form, and when to leave more than one form?

    Natural selection isn’t intelligent: it doesn’t decide anything. It’s a process that just happens. Saying that natural selection decides what is fitter is about as sensible as saying that the earth decides to pull things towards it through gravity.

    Bob

  27. Bob: “Natural selection isn’t intelligent: it doesn’t decide anything. It’s a process that just happens. Saying that natural selection decides what is fitter is about as sensible as saying that the earth decides to pull things towards it through gravity.”

    Bob, you’re stating the obvious and are being blind to the implication of what we’re dealing with. Obviously, NS isn’t intelligent. In fact, NS probably doesn’t even exist. We have genomes stochastically interacting with changing environments, and, over large geographic ranges, this leads to what we call “species”, and we, mistakenly, call that NS. We then extend what we see on a small temporal span, and call that macroevolution over geologic time scales, or what we commonly understand as “evolution.”

    IF—that’s right, “if”—NS exists, then why does it act one way one time, and then a completely antithetical way another time. You simply dismiss this as some trivial anomaly, and no more. Well, there are logical implications to what we see happening in nature. Only reasoning beings have the power to “choose” between alternatives based on some ultimate good (teleology). If you say NS is not intelligent, then you’re saying NS is incapable of explaining what we see happening in this species of flies (fruit flies).

    So what is the causal mechanism here since, per your statement, it can’t be NS?
    Or, do we simply say that NS chooses one form (the “fittest”) over all over forms, unless, of course, it chooses two forms (the “joint fittest”) over all others. This last sentence is just gibberish. So where does this leave a thinking person?

  28. I can understand how humans can be and often are self-contradictory. But here we have a self-contradictory unintelligent process that is incapable of making any decisions whatsoever. Perhaps it’s not as unintelligent as we suppose, lol. Maybe natural selection is entirely human.

    Bob O’H does a great job of avoiding the question by throwing up the red herring. But the question remains.

    How can a process which is incapable of making decisions be self-contradictory. It cannot choose. This is what PaV is pointing out, not that the process is intelligent and can make actual choices. The problem here is that the theory states that it CANNOT make choices. So why does it appear to be doing so?

  29. Another lost reply =P. I’ll have to start saving them before hitting submit I guess.

    In summary: The theory states that the process is incapable of making decisions. So why does it appear to be doing just the opposite of what the theory states?

    It’s not supposed to have any choice in the matter.

  30. “Natural selection isn’t intelligent: it doesn’t decide anything. ”

    No kidding. Like as if IDists don’t know this.

    Terminology like “decide” can be and is used given the lack of better terminology. It’s a common metaphoric tool used when describing natural things.

    One might use “acted upon”, “determined” or any of several other words to describe what PaV is trying to get at. It also seems apparent that you ignored his use of quotation marks around the word decide. Another common tool used to indicate a metaphoric use of terms.

    Otherwise, why are Darwinists constantly using the word “design” when describing things they claim are the result of purely non rational processes?

    BTW, it was creationist Edward Blyth from whom Darwin took many of his ideas and the concept of NS.

  31. Mung – the theory of gravity can’t make a decision either. So why does it decide that apples will fall on the heads of millenarianist physicists?

    Borne – I think you were unfortunate in not seeing Mung’s reply before you posted. :-(

    The problem here is that people are thinking in terms of teleology, and the idea that natural selection has some choice. It’s granting natural selection some level of agency, which it simply doesn’t have.

    The problem is not just one of terminology – it’s the ideas which underlie them, and in particular that natural selection is an agent. If people can see that that isn’t true, and instead see natural selection as a process, then the language they use to describe it will change.

    Bob

  32. Actually, I thought I was arguing the exact opposite, lol!

    Natural selection is supposed to be deterministic and incapable of doing anything other than what it does, for it has no choice in the matter.

    So how is it (natural selection) “making an exception” in this case?

  33. PaV (27): Or, do we simply say that NS chooses one form (the “fittest”) over all over forms, unless, of course, it chooses two forms (the “joint fittest”) over all others. This last sentence is just gibberish. So where does this leave a thinking person?

    This is where: “Fitness” is an empty concept.

    In the discussion of NS here about a month ago, http://www.uncommondescent.com.....-darwinian (already mentioned by Atom above), scordova pointed (in comment #116) to an essay in which Richard Lewontin, a leading Darwinist, basically admits that it’s a worthless concept. (Thanks, Sal.) From Lewontin’s “Four Complications in Understanding the Evolutionary Process” (2003) :

    The difficulties of the concept of fitness are, unfortunately, much deeper than the problem of frequency and density dependence. 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.

    It is the case that all the information about the relative reproductive behavior of types in the population is contained in the complete … schedules of all the genotypes (and, for sexually reproducing species, the age schedule of mating pairs and the frequencies of the different types). Yet this complete reproductive information is insufficient to predict whether a type will increase or decrease in frequency in the population!

    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.

    (Boldface added.)
    __________

    Charles Darwin, On the Origin of Species:

    I have called this principle, by which each slight variation, if useful, is preserved, by the term natural selection, in order to mark its relation to man’s power of selection. But the expression often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate, and is sometimes equally convenient.

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