dubois@uwmacc.UUCP (Paul DuBois) (07/23/85)
>>> [Rich Rosen] >>> What natural selection and evolution "predict" is that, for that set of >>> circumstances that occurs over a period of time, the organisms that >>> survive that period will be the ones best suited for those >>> circumstances, and those of course will be the ones that produce the >>> offspring that follow into the next period. >> [Paul DuBois] >> Rich, this is simply unworthy of you. They "predict" that fitter >> organisms will survive? >> ProFOUND. > [Mike Huybensz] > Paul, are you incapable of reading beyond the first clause? First we need to establish that I can read. I'm not too hopeful. > The key part is that the surviving organisms will be the ones to > reproduce, passing on their characters to the next generation. Thus, > the distribution of characters changes over the generations, producing > a better adapted population. Yes, yes, grok, grok. > Of course you can respond "ho hum" to this too; I wouldn't be surprised, > since it has more than one sentence. Ok, I won't respond that way, since the problem itself is interesting - if facile paperings-over of it (like yours) are not. Your comment reminds me, though, of a mild lecture I received from you once, remonstrating with me for (supposedly) engaging in _ad hominem_ attacks. I guess you don't really mind, since you'll "stoop" to it yourself. :-) --- Before going further, let me make two observations about what follows: (a) I am not trying to bring up a problem just so I can fling it into the teeth of evolutionists, so don't take it that way. (b) what follows does not necessarily have anything to do with evolution (defined as "the production of new organisms from old"), at least it has nothing to do with it without additional elaboration of the situation that was described by Rich. The problem is more general, and is deserving of more widespread attention from creationists than it has so far received. To proceed: I said "proFOUND" because what Rich said was in a sense obvious. The basic idea is quite beguiling, though, and not least because of its simplicity. It "does express an idea which seems correct", and it *does* have a certain charm and beauty, which even I will admit to an appreciation of, hardcore creationist though I am (and I am). But I'm not about to accept it just because it is charming and beautiful. Ok. Now, as I said, Rich's statement is obvious; what else would you (or anyone, even the most ignorant backwoods imbecile) expect? The simple statement is: Fit organisms survive to posterity. But that, perhaps, collapses the idea a little too much. Rich said, somewhat differently, "What natural selection and evolution 'predict' is that, for that set of circumstances that occurs over a period of time, the organisms that survive that period will be the ones best suited for those circumstances, and those of course will be the ones that produce the offspring that follow into the next period." But when we say that, are we really saying anything? Not that I can tell. At least nothing that means anything. The statement is more elaborate and subtle than "survivors survive", but it's no different, really. We went through this all several months ago, and while my recalcitrance at accepting this triviatum seemed to arouse a lot of indignation, no one really addressed problem. Neither have you, Mike. You've dressed it up in yet another set of words, but they boil down to the same obvious statement. In fact, the thing is *so* obvious, I'm inclined to wonder if it is even right. After wondering, I don't think it is. I do not see, for example, the justification for the functional link made between reproduction and survival that is used as the criterion of fitness. What does "survive" in Rich's statement mean? Presumably not that they don't die, for all organisms do. Also presumably not that they reproduce more, or else the statement reduces immediately to a tautology that is not interesting. So it seems to mean "they live longer than organisms which are not so fit". (If all this seems obvious to you, please forgive me. Console yourself with the thought that I'm just trying out possibilities to see if I've reached the stage of formal operations yet.) So the ones that survive "circumstances" will be the ones to pass genes to the next generation. But at this point I start to wonder: what are the others doing in the meantime, *before* they die? Consider population x, with two subpopulations of organisms x1 and x2. Organism type x1 lives until age a1, at which time it drops over dead. But during that time it breeds like a rabbit, at rate r1. Organism type x2, on the other hand, breeds more slowly, at rate r2, but lives longer, to age a2. Let's say the difference is due to a genetic linkage which results in reproductive acceleration at cost of lifespan. That is, r1 > r2 a1 < a2 So x1 leaves a lot of offspring, but does not survive very well itself. It breeds a lot and then kicks off. x2 does not leave many offspring, but survives much longer. Which is fitter? I personally would say x2 because it lives longer, i.e., it survives. But since x1 leaves more offspring it passes more genetic material to posterity. So by definition it is fitter: it enjoys reproductive success. But in fact, all we know for sure is that x1 is more numerous. We do not really know if it is fitter. Its numerosity may have nothing to do with fitness, except in the trivial sense that fitness is measured by reproductive success. We say that the ones that are fit will be the ones that reproduce. It would be more accurate to say that the ones that reproduce will be the ones to reproduce. They may not be the ones surviving the longest. Maybe they're good at reproducing and nothing else. Of course, my own personal choice of x2 is questionable; it depends what level you look at. At the level of the group, x1 is fitter; it propagates more. At the level of the individual, x2 is fitter; it survives longer. Natural selection (now) refers to populations; presumably x1 is fitter according to that view. Somewhere in here lurks a problem, which is (from my point of view) a paradox, and which seems (to me) wrong. The paradox (to me) is that x1, the crappy organism (by my standards), is judged fitter because it satisfies the criterion of reproductive success better. A poorer organism produces a fitter population because of the way fitness is defined. This leaves me feeling, to say the leaast, somewhat ambivalent. Now of course we need definitions, but not definitions that "solve" problems which should be investigated empirically. Here I throw up my hands and "resolve" the paradox by deciding that the criterion of fitness is worthless. (I put "resolve" in quotes because obviously this decision does not advance us very far.) The error (as it seems to me) is that the link between survival and reproduction in assessing fitness is unnecessary, or at least poorly-defined or wrong. It *seems* to me (I may be wrong, so no flames - just point out my error) that the two are tied together in a way that cannot logically be required: there is no necessary relationship between survival of the "fit" individual (measured by lifespan) and generation of the next "fit" population (measured by reproductive success). By saying that the ones that survive reproduce more (that is what Rich said, and what Mike I think defended), one makes this link. But on what basis? I assume on this basis: the ones that survive longer, leave more offspring *all other things being equal*. I suppose they will - but why make this assumption? Things are not obviously equal. To make the theory work? Not a chance. It has to be *shown*, not assumed. In my example, it's false. Its not a thing to be considered true or false a priori, but something to be *found out*. Otherwise, someone can just come along and cook up one of these ad hoc stories like, "the ones that live for a shorter time will be selected for maximum reproductive rate, and thus will be at no disadvantage." Well, sure. But so will the ones that live longer. If we take that route, the criterion, reproduction, is what gets selected for, not something else. We end up with a view of organisms that are adapted *to reproduce*. But that was the way they *expressed* their fitness, I thought, not the thing they were supposed to be fit at doing. Let us go back a little. Those which are fitter will leave more offspring but only true if fit *to leave offspring* or, if fitness *is defined as* leaving more offspring and then "fitness" is meaningless, because it says nothing. Try it - make the substitution of variables: fitness = fit to leave offspring, yields Those which are fit to leave more offspring will leave more offspring fitness = leaving more offspring, yields Those which leave more offspring will leave more offspring Not very illuminating. Hence my frequent comments in the past about vacuity. Let me raise an objection against what I have just written. As indicated above, fitness is measured by differential reproductive success. Now, at this point, millions of critics have risen up and cried "tautology!" One asks, "which are the fittest?" "Those that survive." "Which survive?" "The fittest." "Oh..." But that view *equates* fitness with differential success, and that is ... (remembernowIamacreationistsoholdyourbreath) ... incorrect! (Although this mistake is often made, e.g., by evolutionists accepting too easily the words of their evolutionary mentors.) As an alternative, it is possible to construct the following view. I will try to make my thinking explicit. First, we must observe that "fitness is measured by differential reproductive success" and "fitness is differential reproductive success" are two *different* statements. If this is kept in mind, the tautology may disappear (I'm not convinced that it does, but I suspect that it might). Organisms are or are not fit. Fitness is the thing we want to measure, but how do we do it? We can say that fitness is some abstract quantity, but which is a covert variable, not directly observable. So we need an overt variable that we can hang a number on. The overt variable needs to be in some sort of relationship to fitness, and reproductive success is thought to have that characteristic. If the relationship is strong, then we have in differential success a good indicator of the fitness of the population. My question is: how do we know that differential reproductive success is a valid indicator? My answer is that we don't. It is thought to be so, but I'm skeptical. Is an increased number of offspring a necessary consequence of fitness? I don't think so. At the very least, our covert variable, fitness, is confounded with something else, i.e., reproductive *ability*. Differential reproductive success is in part or whole a function of reproductive ability. I do not think this can be disputed. It may also be, and probably is, a function of other factors, among which fitness may well number. That is, drs = f (reproductive ability, fitness?, ... ) But we certainly do NOT have drs = f (fitness only) If anyone thinks that the latter is true, then I invite you to demonstrate how we may decouple fitness from reproductive ability, for that must be done to use differential reproductive success as a valid indicator. I think that much of the problem arises from the fact that we don't really know what fitness *is*. Everybody has some intuitive idea about it. The reproductive stuff is one of them. Obviously I believe that's an incorrect intuition, and disintegrates under scrutiny. But if fitness is defined some other way, e.g., ability to live longer, then there is no necessary link with reproductive capacity. And then, I think, the whole thing falls apart. We need a new view ("one that won't make my eyes turn red..."). I wish I had it. I know I'm better at criticizing than constructing, and though I think this is constructive criticism of a sort, I haven't gotten further than the above, so far. --- Final jab: It is interesting (to me at least), that creationists are said not to know what evolution is, and so are consequently said not to know what they are criticizing. This is often true, unfortunately. But I suspect, more strongly as time goes by, that many evolutionists don't know what they are *defending*! Witness the recent posting in which someone spouted the Darwinian orthodoxy, right down the line, as though it were considered credible today. Right out of his high-school textbook, I suppose. Witness also the great importance attached to natural selection by many on this net. But how important is it in recent evolutionary theory? Not very, in a number of instances. Michael Lonetto has shown evidence that he knows this. How many others? Rich is (apparently) still in the dark ages, carrying this (apparently) *unexamined conviction* around. Mike H might be, but I doubt it; I suspect that he was trying to clarify what Rich said, rather than defend it as his own position. In any case, what natural selection *is*, how one detects its absence or presence, how one measures its intensity of effect, are questions that have all gone largely unanswered and are solved, as far as I can see, largely by definition. What we see in the postings are vague generalizations, or "there's a lot of research on it today". I am not satisfied with this, and it would be a shame if anyone else was either, particularly evolutionists. I suspect that such comments are smokescreens, serving as substitutes for thought. I certainly do *not* accept the pontifications about it, as if I should just shut up and believe the (current) revealed wisdom. -- | Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois --+-- | "More agonizing, less organizing." |
throopw@rtp47.UUCP (Wayne Throop) (07/26/85)
It seems that a lot of the discussion in the referenced posting is based on a misperception. In particular: > So x1 leaves a lot of offspring, but does not survive very well > itself. It breeds a lot and then kicks off. x2 does not leave many > offspring, but survives much longer. > > Which is fitter? There is the implicit assumption that there is a linear scale of "fitness". This is a deeply rooted problem that appears in many places. IQ, testing for an ominous example. Resteraunt grading for another. After all, which tastes better, Cajun cooking or German? I would say then that much of what followed is bogus, since it is based on the notion that natural selection is based on an absolute fitness scale. Natural selection is based more on competition for available resources. Some other specific points: > The error (as it seems to me) is that the link between survival and > reproduction in assessing fitness is unnecessary, or at least > poorly-defined or wrong. It *seems* to me (I may be wrong, so no > flames - just point out my error) that the two are tied together in a > way that cannot logically be required: there is no necessary > relationship between survival of the "fit" individual (measured by > lifespan) and generation of the next "fit" population (measured by > reproductive success). The relationship seems clear to me. Most organisms cannot (or likely do not) reproduce at all until a certain age, and then they reproduce for at some rate *after* that age. Therefore an organism must first live long enough to reproduce at all. Then, the longer-lived organisms will produce more total offspring, since number of offspring is the rate of reproduction times the length of time spent reproducing. Thus, there is a simple and direct relationship between lifespan and reproductive success (where lifespan is (perhaps) one component of fitness). > By saying that the ones that survive reproduce more (that is what Rich > said, and what Mike I think defended), one makes this link. But on > what basis? I assume on this basis: the ones that survive longer, > leave more offspring *all other things being equal*. I suppose they > will - but why make this assumption? Things are not obviously equal. > To make the theory work? Not a chance. It has to be *shown*, not > assumed. Nonsense. This is just what is done in physical systems, such as relating temperature, pressure, volume, and so on. The assumption of "other things being equal" isn't needed to make the theory work. It just makes it clear what happens *if the assumption is so*. If other things are *not* equal, there will still be *benefit* to being (say) longer lived. > But we certainly do NOT have > > drs = f (fitness only) Quite so. But longevity (what you seem to be calling fitness here) *does* bestow relative reproductive advantage. > [...] > demonstrate how we may decouple fitness from reproductive ability, for > that must be done to use differential reproductive success as a valid > indicator. No it mustn't. I'm not at all sure what makes Paul think it must. > Witness also the great importance attached to natural selection by many > on this net. But how important is it in recent evolutionary theory? > Not very, in a number of instances. Michael Lonetto has shown evidence > that he knows this. How many others? Rich is (apparently) still in > the dark ages, carrying this (apparently) *unexamined conviction* > around. Mike H might be, but I doubt it; I suspect that he was trying > to clarify what Rich said, rather than defend it as his own position. I don't follow this at all. Perhaps some of the enlightened, such as Michael Lonetto, would let me in on the secret. In what way is natural selection unimportant to "recent" evolutionary theory. > Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois -- Wayne Throop at Data General, RTP, NC <the-known-world>!mcnc!rti-sel!rtp47!throopw
friesen@psivax.UUCP (Stanley Friesen) (07/30/85)
In article <1318@uwmacc.UUCP> dubois@uwmacc.UUCP (Paul DuBois) writes: > >To proceed: > >What does "survive" in Rich's statement mean? Presumably not that they >don't die, for all organisms do. Also presumably not that they >reproduce more, or else the statement reduces immediately to a >tautology that is not interesting. So it seems to mean "they live >longer than organisms which are not so fit". > In point of fact, the real meaning in evolutionary theory *is* that they reproduce more, even if you think that is an uninteresting tautology! From an evolutionary standpoint longer life is only meaningful if it leads to more reproduction. What is actually significant is extended reproductive success of a genotype. That is an organism which produces so many offspring that they all starve has a lower effective reproductive rate than one which only produces as many offspring as can survive! > >Of course, my own personal choice of x2 is questionable; it depends >what level you look at. At the level of the group, x1 is fitter; it >propagates more. At the level of the individual, x2 is fitter; it >survives longer. > But you see, evolution operates at the *group*(i.e population) level, so that *individual* "fitness" is only significant as a component of population fitness. >Natural selection (now) refers to populations; presumably x1 is fitter >according to that view. Somewhere in here lurks a problem, which is >(from my point of view) a paradox, and which seems (to me) wrong. The >paradox (to me) is that x1, the crappy organism (by my standards), is >judged fitter because it satisfies the criterion of reproductive >success better. A poorer organism produces a fitter population because >of the way fitness is defined. This leaves me feeling, to say the >leaast, somewhat ambivalent. Now of course we need definitions, but >not definitions that "solve" problems which should be investigated >empirically. Here I throw up my hands and "resolve" the paradox by >deciding that the criterion of fitness is worthless. (I put "resolve" >in quotes because obviously this decision does not advance us very >far.) > Ah, but you are confusing the scientific concept of "biological fitness" with the human valuation of fitness. They are seperate ideas. So you prefer organism x2 - fine! But that has nothing to do with science, or the *scientific* concept of fitness. >The error (as it seems to me) is that the link between survival and >reproduction in assessing fitness is unnecessary, or at least >poorly-defined or wrong. It *seems* to me (I may be wrong, so no >flames - just point out my error) that the two are tied together in a >way that cannot logically be required: there is no necessary >relationship between survival of the "fit" individual (measured by >lifespan) and generation of the next "fit" population (measured by >reproductive success). > Quite true! In fact serious evolutionary theorists make no such claim! If we did we would have a hard time explaining annual plants and such like! >By saying that the ones that survive reproduce more (that is what Rich >said, and what Mike I think defended), one makes this link. But on >what basis? I assume on this basis: the ones that survive longer, >leave more offspring *all other things being equal*. I suppose they >will - but why make this assumption? Things are not obviously equal. >To make the theory work? Not a chance. It has to be *shown*, not >assumed. In my example, it's false. Its not a thing to be considered >true or false a priori, but something to be *found out*. > Actually, they are simply speaking imprecisely. There is a demonstrable connection in organisms that reproduce more than once and/or require time to reach reproductive maturity. An organism that fails to reach reproductive maturity has left *no* offspring, so survival longer *can* increase reproduction, and with multiple reproduction longer life generally allows more reproduction events! This is still secondary however. >Let us go back a little. > >Those which are fitter will leave more offspring > but only true if fit *to leave offspring* > or, if fitness *is defined as* leaving more offspring > >and then "fitness" is meaningless, because it says nothing. Try it - >make the substitution of variables: > Ah, but you are treating fitness as a valuation when it is a *measure*. That is fitness is the *measure* of how well an organism does at reproducing itself. The key is to then calculate the *effect* of leaving more offspring on the genetic composition of the whole population, the result of this mathematical model is *changed gene ratios* in which those genes that contributed most to reproductive success have increased the most. Now apply this repeatedly to each generation and you have evolution! To show evolution does not occur youy must now show one of a) solid limitations on variation exist, b) that gene ratios do not change, or c) that genes do not effect reproductive success(i.e. fitness). > fitness = fit to leave offspring, yields > Those which are fit to leave more offspring will leave more offspring > > fitness = leaving more offspring, yields > Those which leave more offspring will leave more offspring > >Not very illuminating. Hence my frequent comments in the past about >vacuity. Mainly because such statements have nothing to do with evolution. The real statement is "Fitness(i.e. reproductive success) causes increased representation in the next generation of similar individuals". > >Let me raise an objection against what I have just written. As >indicated above, fitness is measured by differential reproductive >success. Now, at this point, millions of critics have risen up and >cried "tautology!" One asks, "which are the fittest?" "Those that >survive." "Which survive?" "The fittest." "Oh..." > I repeat, fitness *is* the measure of reproductive success. >But that view *equates* fitness with differential success, and that >is ... (remembernowIamacreationistsoholdyourbreath) ... incorrect! Exactly! Except that it is correct, by *definition*, since that is how we biologist define fitness. >--- > >Final jab: > >It is interesting (to me at least), that creationists are said not to >know what evolution is, and so are consequently said not to know what >they are criticizing. This is often true, unfortunately. But I >suspect, more strongly as time goes by, that many evolutionists don't >know what they are *defending*! Witness the recent posting in which >someone spouted the Darwinian orthodoxy, right down the line, as though >it were considered credible today. Right out of his high-school >textbook, I suppose. > Mainly because most of the evolutionary supporters on the net on not biologists, only laymen with an interest in the subject, which may often be somewhat of date. >Witness also the great importance attached to natural selection by many >on this net. But how important is it in recent evolutionary theory? >Not very, in a number of instances. Michael Lonetto has shown evidence >that he knows this. How many others? Rich is (apparently) still in >the dark ages, carrying this (apparently) *unexamined conviction* >around. Mike H might be, but I doubt it; I suspect that he was trying >to clarify what Rich said, rather than defend it as his own position. > Actually, it is still *very* important, except among certain extreme schools of evolutionary thought such as the most extreme forms of Punctuate Equilibrium and the "neutralist" theories of many microbiologist(who have little experience with organisms under natural conditions). >In any case, what natural selection *is*, how one detects its absence >or presence, how one measures its intensity of effect, are questions >that have all gone largely unanswered and are solved, as far as I can >see, largely by definition. > Well, I gave a simple definition above. And definition is a perfectly valid approach to a problem, provided it fits with the data! Look at how physicist approach the concept of mass. It is simply *defined* as the measure of resistance to acceleration! Or if you use the approach you used above for "fitness" this becomes "Mass is what mass is" by substitution of variables. -- Sarima (Stanley Friesen) {trwrb|allegra|cbosgd|hplabs|ihnp4|aero!uscvax!akgua}!sdcrdcf!psivax!friesen or {ttdica|quad1|bellcore|scgvaxd}!psivax!friesen
keithd@cadovax.UUCP (Keith Doyle) (07/30/85)
......... >Of course, my own personal choice of x2 is questionable; it depends >what level you look at. At the level of the group, x1 is fitter; it >propagates more. At the level of the individual, x2 is fitter; it >survives longer. It's even more complicated than that. In an environment where it is most important to reproduce, then x1 is better, where it is not so important (maybe overpopulation causes most of them to die anyway) then they may be on equal terms or even x2 could have the advantage (perhaps an animal being pregnant might be more succeptible to predation for various reasons). >empirically. Here I throw up my hands and "resolve" the paradox by >deciding that the criterion of fitness is worthless. (I put "resolve" The criterion of fitness is not absolute, but relative (to the complex details of the individual environment). You seem to want to pigeonhole the criteriae for fitness in some sort of absolute value system. >By saying that the ones that survive reproduce more (that is what Rich >said, and what Mike I think defended), one makes this link. But on >what basis? I assume on this basis: the ones that survive longer, >leave more offspring *all other things being equal*. I suppose they >will - but why make this assumption? Things are not obviously equal. >To make the theory work? Not a chance. It has to be *shown*, not >assumed. In my example, it's false. Its not a thing to be considered We cannot assume it is false without more details. Under some circumstances x1 is fitter, under others x2. There is no all pervasive criteria for judging the fitness of x1 and x1. >like, "the ones that live for a shorter time will be selected for >maximum reproductive rate, and thus will be at no disadvantage." Well, >sure. But so will the ones that live longer. If we take that route, >the criterion, reproduction, is what gets selected for, not something >else. We end up with a view of organisms that are adapted *to >reproduce*. But that was the way they *expressed* their fitness, I Effectively, that is what we have. However, an immense variety of characteristics and conditions can interplay to make up relative fitness for reproduction. In addition, various characteristics may be intertwined with characteristics that have very little to do with reproduction, thus causing them to be 'carried along' with the more important selection characteristics. The basic ability to survive is intertwined with the ability to reproduce. The ability to feed oneself and avoid predation is intertwined with the ability to survive. The ability to keep from freezing in cold climates may be intertwined if an organism lives in the cold etc. >Those which are fitter will leave more offspring > but only true if fit *to leave offspring* > or, if fitness *is defined as* leaving more offspring > >and then "fitness" is meaningless, because it says nothing. Try it - >make the substitution of variables: > > fitness = fit to leave offspring, yields > Those which are fit to leave more offspring will leave more offspring > > fitness = leaving more offspring, yields > Those which leave more offspring will leave more offspring > >Not very illuminating. Hence my frequent comments in the past about >vacuity. I would say that it in itself is awfully obvious. Apparently it's entertwinement with evolutionary theory is where it becomes confusing (thus the apparent repeated confusion on N.S. and relateds in this discussion). >Is an increased number of offspring a necessary consequence of >fitness? I don't think so. Is it a necessary consequence of survival? Not necessarily, as before, the number of offspring may have nothing to do with reproductive success. An organism that only has one offspring but can protect it from predation better than another organism that has umpteen offspring, may achieve higher reproductive success. >At the very least, our covert variable, fitness, is confounded with >something else, i.e., reproductive *ability*. Differential >reproductive success is in part or whole a function of reproductive >ability. I do not think this can be disputed. It may also be, and >probably is, a function of other factors, among which fitness may well >number. That is, > > drs = f (reproductive ability, fitness?, ... ) > >But we certainly do NOT have > > drs = f (fitness only) Here I would almost agree. I would say that drs is equivalent to f, but that; drs = f = (reproductive ability, longevity, fertileness, ability to cope with present environmental concerns, ability to avoid predation,.........) Only because I define fitness as drs. Your definition of fitness seems to be some personal subjective judgement. You have to ask, fitness for what? I would respond, to reproduce. Perhaps you have a different answer here. >If anyone thinks that the latter is true, then I invite you to >demonstrate how we may decouple fitness from reproductive ability, for >that must be done to use differential reproductive success as a valid >indicator. Valid indicator of what? DRS is a mechanism for filtering out harmful (to DRS) mutations, and preserving useful ones. Sure, DRS=F dosen't say much, it's ridiculously obvious. It's effect as a filter and as an adaptation mechanism is where it all gets interesting. >But if fitness is defined some other way, e.g., ability to live longer, >then there is no necessary link with reproductive capacity. And then, >I think, the whole thing falls apart. No, the bottom line is, the ability to produce offspring that survive. Its just that: DRS <> (quantity of offspring) or DRS <> (longevity) or etc.... because there are all kinds of other factors. In addition, characteristics that are neutral with regard to DRS, are not necessarily filtered out in the process, though they may later resurface and become non-neutral if other considerations (environment, related characteristics, etc.) change. >Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois --+-- Keith Doyle # {ucbvax,ihnp4,decvax}!trwrb!cadovax!keithd
dsf@allegra.UUCP (dave fox) (07/30/85)
It is not tautological, it is not paradoxical, it is not vacuous. It is just very simple: The organisms we see around us are those whose parents did not die until after they were born.
kst@telesoft.UUCP (Keith Thompson @stroke) (08/02/85)
In article <1318@uwmacc.UUCP> dubois@uwmacc.UUCP (Paul DuBois) writes: > ... > Organisms are or are not fit. Fitness is the thing we want to measure, > but how do we do it? We can say that fitness is some abstract > quantity, but which is a covert variable, not directly observable. So > we need an overt variable that we can hang a number on. The overt > variable needs to be in some sort of relationship to fitness, and > reproductive success is thought to have that characteristic. If the > relationship is strong, then we have in differential success a good > indicator of the fitness of the population. My question is: how do we > know that differential reproductive success is a valid indicator? My > answer is that we don't. It is thought to be so, but I'm skeptical. > Is an increased number of offspring a necessary consequence of > fitness? I don't think so. > ... Differential reproductive success is indeed the key issue here. This is, by definition, the *only* indicator of the fitness of a population. Specifically, "fitness" is the set of characteristics that tend to result in reproductive success. (This is my personal definition; I don't claim that biologists define the term the same way.) What these characteristics are depends on what kind of environment the organism lives in. Longevity is certainly one characteristic that contributes to fitness (the longer an organism lives, the more time it has to reproduce), but by no means the only one. I would say that the common housefly is considerably more successful as a species than, say, the Galapagos tortoise. Note that what I have stated so far is a definition, not a (testable) theory. What the theory of evolution by natural selection states, as I understand it, is that there are indeed such characteristics, and that they can be passed on to an organism's descendants. In other words: (1) Reproductive success is (at least partially) a result of certain characteristics inherent to an organism; it is not purely a result of random chance. (2) These characteristics can be passed on; successful organisms tend to have successful offspring (and lots of them). Note that there is a distinction between fitness and success. Fitness is a set of characteristics inherent to an individual or species. Success is an observable *result* of fitness. Note that success can be a result of things other than fitness. For example, blind luck can play a significant role. The more recent "post-Darwinian" theories of evolution focus on factors other than natural selection. However, natural selection still plays a major part (I think). Given that mutations occur, creating a large pool of different characteristics in a population, and that some small fraction of these mutations result in greater "fitness", and thus in differential reproductive success, how can evolution *not* occur? Comments appreciated; flames to /dev/null. -- The_Other_Keith -- "Inevitably, their affair ended: Howard worried excessively about what the pack would think, and Agnes simply ate the flowers."
dubois@uwmacc.UUCP (Risky Rat) (08/05/85)
>> [Paul DuBois] >> Witness also the great importance attached to natural selection by many >> on this net. But how important is it in recent evolutionary theory? >> Not very, in a number of instances. Michael Lonetto has shown evidence >> that he knows this. How many others? Rich is (apparently) still in >> the dark ages, carrying this (apparently) *unexamined conviction* >> around. Mike H might be, but I doubt it; I suspect that he was trying >> to clarify what Rich said, rather than defend it as his own position. > [Wayne Throop] > I don't follow this at all. Perhaps some of the enlightened, such as > Michael Lonetto, would let me in on the secret. In what way is natural > selection unimportant to "recent" evolutionary theory. I misspoke somewhat. What I should have said, was that natural selection is considered unimportant more and more in regard to *speciation* - not evolution in general. (My reference to Michael L was in regard to his posting on speciation in Drosophila.) Anyway, to clarify, my favorite passage comes from: Stephen Jay Gould, "Is a new and general theory of evolution emerging?", _Paleobiology_, 6(1), 1980, 119-130. The control of evolution by selection leading to adaptation lies at the heart of the modern synthesis. Thus, reproductive isolation, the definition of speciation, is attained as a by-product of adaptation -- that is, a population diverges by sequential adaptation and eventually becomes sufficiently different from its ancestor to foreclose interbreeding. (Selection for reproductive isolation may also be direct when two imperfectly-separate forms come into contact.) But in saltational, chromosomal speciation, reproductive isolation comes first and cannot be considered as an adaptation at all. It is a stochastic event that establishes a species by the technical definition of reproductive isolation. To be sure, the later success of this species in competition may depend upon its subsequent acquistion of adaptations; but the origin itself may be non-adaptive. We can, in fact, reverse the conventional view and argue that speciation, by forming new entities stochastically, provides raw material for selection. [page 124] I highly recommend this paper. It is my impression that Gould is very popular in this newgroup but that few have read more than his popular books and/or his essays in Natural History. -- | Paul DuBois {allegra,ihnp4,seismo}!uwvax!uwmacc!dubois --+-- | Ritual and Ceremony: Life Itself. |
friesen@psivax.UUCP (Stanley Friesen) (08/10/85)
In article <1361@uwmacc.UUCP> dubois@uwmacc.UUCP (Risky Rat) writes: > >I misspoke somewhat. What I should have said, was that natural >selection is considered unimportant more and more in regard to >*speciation* - not evolution in general. > Well, I would not say "more and more". There is currently considerable controversy over this issue, and it is not at all clear which way it is actually shifting. There is much new evidence that coontradicts the predictions of the P.E. purists. Thus the theory may actually be tending towards some sort of middle ground. >Anyway, to clarify, my favorite passage comes from: > > Stephen Jay Gould, "Is a new and general theory of evolution > emerging?", _Paleobiology_, 6(1), 1980, 119-130. > > come into contact.) But in saltational, chromosomal speciation, > reproductive isolation comes first and cannot be considered as an > adaptation at all. It is a stochastic event that establishes a > species by the technical definition of reproductive isolation. To > be sure, the later success of this species in competition may > depend upon its subsequent acquistion of adaptations; but the > origin itself may be non-adaptive. We can, in fact, reverse the > [page 124] > Note, that he is here only talking about one kind of speciation, chromosomal speciation. This by no means the *only* kind of speciation, and I do not think even Dr Gould would claim it is the most important mode of speciation. Very few other types of speciation have actually been well verified as even being possible, so this leaves this as a rather special case. >I highly recommend this paper. It is my impression that Gould is very >popular in this newgroup but that few have read more than his popular >books and/or his essays in Natural History. > Well, I do have a lot of respect for him, although I am far from agreement with him on many points. Certainly his books are worth reading, as an introduction to one school of thought among modern biologists. -- Sarima (Stanley Friesen) {trwrb|allegra|cbosgd|hplabs|ihnp4|aero!uscvax!akgua}!sdcrdcf!psivax!friesen or {ttdica|quad1|bellcore|scgvaxd}!psivax!friesen