Biological fitness - What Is It? (Page 3)

CoIin: Moving on.. and let's ignore the unit of selection, if that's ok?

This website seems very helpful, although I've no idea of its reliability. I just found it at random.

http://www.willus.com/mingw/colinp/fitness.html

The last time Corvin posed his challenge, I had responded that the challenge was unreasonable on the grounds that, since fitness is DEFINED in terms of survival and reproduction, meeting the challenge is a logical impossibility. This seems to be Geoff's position too.

The problem is though, if this were the case, Darwinism would be vulnerable to accusations of circularity.

If the article on the website is correct, and it's explained very clearly ( ), then I was wrong previously and survival/reproduction should be regarded as an INDICATOR of fitness, rather than the definition of fitness. There IS something in organisms that makes them fit. Survival rates are just an easy way to tell.

Perhaps we could make an analogy with the fuel gauge in a car and the petrol in the tank. The fuel gauge pointing to zero tells us that the tank is empty, but it is not the DEFINITION of the tank being empty. There IS more to the fuel tank being empty than just the needle pointing to zero. In principle at least we could determine that the fuel tank was empty by other means.

If this is correct then meeting Corvin's challenge should be regarded as a practical impossibility (it's just too darn complex! ) rather than a logical impossibility.

Have I got this right yet? Whoever said Darwinism was simple?

CoIin: Moreover, if the above is true, then (hypothetically) those who got a helping hand from You-Know-Who would not necessarily be the fitter. Right?

It's just that we'd never be able to tell.

CoIin: So once again, a Wordy analogy may be enlightening

Let's say that the cheats who use a word generating programme have been "given a helping hand by God". And let's assume that they tend to win due to this divine assistance. They would tend to lose otherwise. And they do lose whenever God decides to withdraw the privilege.

So, are the cheats the "fittest"?

1. If we define the fittest as simply the winners, then yes, the cheats are the fittest. In this case Corvin's challenge could never be met - it's logically impossible.


2. If fitness is not simply a matter of winning - if it depends on the natural endowments of the player - then no, the cheats are not the fittest. I could legitimately say to a cheat, "Yes, you won, but I'm a better player."

In this case the win-lose distinction is not isomorphic with the fit-unfit distinction. The problem is, we only get to see the results. We only see the words that all players make; we have no access to the methods they use.

Therefore, in the case of 2., Corvin's Challenge can still never be met - but for practical rather than logical reasons.

On the other hand, if we could install a camera in every player's home....

duncan124:
That links argument is false.

Darwin did not say fittest ,so its a ' Tautology Argument '' itself.

There is no 'evolution tool' after 150 years which indicates that it is not scientific.


Darwin was about showing how species are created by change in one species and not about creating an over all design for evolution which others were also writting about and which could have seriously altered the value of his book.

Commom sense tells us that other factors are involved besides ' Natural Selection '. Economics of food supply are just as important as mating and any change in the environment that alters the food alters the species.

It is an interesting idea and might work as far as it goes but it just aint evolution.

His example of birds has been shown to be false and the reason they change is food/environment.

duncan124:
It is a double negative, which promotes a positive which is Darwins views, opinions and values.

CoIin: Another analogy - "Medals for the brave"

(I'm just trying to get my head around this stuff. . Tell me if you think the analogy works. )

Armies containing large numbers of decorated soldiers are brave? Or is it that brave soldiers tend to be awarded medals?




Possibility 1 :- Let's say we define "brave" simply as "possessing medals". Armies whose soldiers possess a lot of medals are brave by defintion. Not every individual soldier will have a medal, but we can say that the more medals an army possesses as a whole, the braver its soldiers.

If this is what it means to be brave, then "brave" and "decorated" are one and the same thing. There is nothing more to be being brave than owning medals. One does not explain the other. Medals are not an indicator of courage; medals ARE courage. If an army has no medals, it is not courageous. Period. If you want to know which armies are relatively brave, just compare their medal counts.

Thus defined, if you were to claim "I think the Russian army fought bravely in such-and-such a campaign, but they won few or no medals" you would have completely misunderstood what it means to be brave. Your claim is as nonsensical as "I think Jim is an academic doctor, but he doesn't have a PhD". To be an academic doctor JUST IS to have a PhD.

To say "They are brave BECAUSE they have medals" or "They have medals BECAUSE they are brave" would be analogous to saying "Opium puts people to sleep BECAUSE it has a dormitive effect" or "Birds are bipeds BECAUSE they walk on two legs", i.e. , to say nothing at all. You are merely restating the definition; you are not explaining anything.

And if Corvin were to challenge us to produce evidence of a more brave army possessing fewer medals than a less brave one, he'd be sending us on a wild goose chase. It's not logically possible.

If this is how we should view "survival of the fittest", then the maxim is entirely circular and vacuous. It tells us nothing. "Fit" just means surviving and multiplying. We could do away with the term "fitness" and just retain "survival", after all they are synonymous.

(This may remind the astute reader of Einstein's equivalence principle. If there is no possible way to tell gravitational mass from inertial mass, they are for all intents and purposes, the same thing.)




Possibility 2 : - It is true that brave soldiers tend to be awarded medals more than cowardly soldiers, but possession of medals is not IDENTICAL to being brave; they are not the same thing. Counting medals provides us with a useful indicator of courage, especially helpful in armies from times long past whose behavior or anatomy cannot be directly observed.

In this scenario, there IS something that distinguishes the Greek army from the Persian army EVEN BEFORE THEY DO BATTLE, even before any medals have been awarded. It may be something physical, but since we're using bravery as our analogy, it's more likely to be something psychological.

This "bravery" may be something that philosophers call a "dispositional quality", which is to say that it is not always apparent (like the shape and size of an object, for example), but only becomes manifest under certain conditions, like "fragility" for instance. There's no way to tell that glass is fragile just by looking at it, you'd have to whack it with a hammer to find out, but fragility is nevertheless a real quality. Reinforced glass and regular glass are not identical, even if we have no way of telling them apart just by looking.

The greater fragility of the regular glass can EXPLAIN its breaking when struck, just as the greater bravery of soldiers can EXPLAIN their possessing more medals. And there are bound to be a few recalcitrant pieces of regular glass which do NOT shatter when struck with a regular whack. . Fragility is a structural feature of the glass, it is not identical to "breaks when struck" although it will tend to do so.

On this view of bravery (analogous to a synthetic or empirical view of biological fitness), if we were smart enough, and assuming we had access to all the relevant variables (topology of the battlefield, weather conditions, [= environment], etc), we WOULD be able to predict the winners, or at least predict which army is statistically more likely to win.

If this is the correct view of biological fitness, then "survival of the fittest" is not merely a tautology. Fitness is not simply survival and multiplication. It is something more. It is the PROPENSITY to survive and multiply (and I think this is the key I missed before). It is a congeries of qualities inherent in the organism which in relation to a given environment will confer advantageous or disadvantageous effects. It is something that in principle, if not in practice, we should be able to access.

If this is the correct view of fitness, then Corvin's challenge could in principle be met, assuming that our ideas about natural selection are mistaken as the Creationists claim. But in this day and age, it would seem a fool's errand. Performing autopsies isn't likely to reveal evidence of courage.

CoIin: OMG! I just had a Eureka moment! The whole thing has finally snapped into place.

Fitness, to be meaningful and vindicate Darwin, must be thought of as a PROPENSITY to survive and reproduce, rather than just the brute fact of surviving and reproducing.

"Survival of the fittest" is not analytic; it is synthetic.



(I've edited my original posts on page 1 slightly to reflect this)

duncan124:
Your problem is you don't know what fit is. We can see that you are not and never have been fit.

...or you would know what the problem with it was.

Your link is unsound from the first lines.

It is odd that you have never thought about fitness and reproduction and it might be your long and odd posts are connected to that weakness.

CoIin: The clarity continues (I think - Just because something clicks into place doesn't mean it clicked into the RIGHT place )

It seems to me that fitness cannot possibly be identified with (i.e. defined by) survival/reproduction rates. This would lead to absurd consequences.

As a thought experiment, let's say we introduce two members of the same species into the same environment. How about two kangaroos - Jim and Dave - not identical, of course, released into the Australian outback.

In the first iteration of our thought experiment, Jim "wins". Jim finds a mate and reproduces. Dave doesn't. Now, if fitness is defined in terms of survival/reproduction (i.e. if fitness is identical with reproductive success) then we must conclude that Jim is fitter than Dave.

We now repeat the thought experiment with the same two kangaroos. In this second iteration, Dave finds a mate and reproduces. Jim doesn't. Therefore we are forced to conclude that Dave is fitter than Jim.

Common sense tells us that such a scenario is quite possible. Alas, we now reach the absurd conclusion that Jim is both more fit AND less fit than Dave!!

What we should say to be correct, I think, is that as the number of iterations increases, or as the number of organisms we are dealing with increases, "fitness" and "survival" will converge asymptotically. For very large numbers of organisms, the two will be virtually indistinguishable. But one is NOT defined in terms of the other.

duncan124:
" Darwin did not say fittest ,so its a ' Tautology Argument '' itself." I said and have said before.


If you had chosen ' Healthy ' instead of ' fittest ' you would have been more sensable then you are.

Helping you out again,... kangaroos are classed as cattle in law and are infact herd animals.

A better example might have been the wild dogs in south USA. These are brutes even if they are the same as domestic dogs and live by killing cattle if they find any.

They are like body builders are when compared to other humans but they live very short lives due to the intense nature of their way of life.

CoIin: Thank God!! A really smart dude to the rescue. Ladies and gentlemen, I give you Alex Rosenberg

The following extract is from his "Philosophy of Science - A Contemporary Introduction"




There is another powerful reason to find the semantic view of Darwinian theory attractive. The problem stems from what is perhaps the oldest and at the same time most vexing problem facing the theory of natural selection. It was a nineteenth-century philosopher, Herbert Spence, who characterized Darwinism as the theory of “the survival of the fittest”, meaning that the fittest will survive to out-reproduce the less fit and by iteration produce evolution. And the label “survival of the fittest” has stuck. Indeed, it is not inapt. For it appears that the central claim of the theory can be expressed as follows in the principle of natural selection (PNS):

PNS Given two competing populations, x and y, if x is fitter than y, then
in the long run, x will leave more offspring than y.

The trouble arises for the theory when we ask what “fitter than” means. If the PNS is to be a contingent empirical law, then one thing we have to rule out is that differences in fitness are defined as differences in number of offspring left in the long run. For that would turn the PNS into the explanatorily uninformative necessary truth that “if x leaves more offspring than y in
the long run, then in the long run x will leave more offspring than y”. Logically necessary truths cannot be scientific laws, and cannot explain any contingent empirical fact. The PNS could explain differences in offspring numbers on this meaning of fitness only if events (like having more offspring) can provide their own explanations – something we ruled out in
Chapter 2.

We could of course refuse to define fitness. Instead we could just hold, along with realists about theoretical entities, that “fitness” is a theoretical term, like “positive charge” or “atomic mass”. But that seems implausible and unsatisfying. After all, we know that taller giraffes and speedier zebras are fitter without the aid of instruments of indirect observation; we know
what fitness is . . . it’s the organism’s ability to solve problems presented to it by the environment: avoiding predators, securing prey, keeping sufficiently warm and dry (unless a fish), etc. But why are these the problems which an organism must solve to be fit? How do they combine into overall fitness? How do we compare organisms for fitness when their abilities to solve any one of these problems differ? The most reasonable answers to these
questions appear that (a) the problems the environment presents organisms with are ones whose solution increases the organism’s chances to survive and reproduce; (b) we can combine the degree to which an organism solves these various problems by measuring the organism’s number of offspring; and (c) two organisms are equally fit, no matter how differently they deal with environmental problems, provided they have the same number of offspring. The only thing wrong with these answers is that they show how almost inevitable the temptation is to define “fitness” in terms of reproduction, thus turning the PNS itself into a definition.

The proponent of the semantic approach to theories has little difficulty with this outcome. The semantic theory can accept that the PNS is a definition; theories are sets made up of definitions like the PNS and claims about the different things in the world that satisfy this definition. The variety of things, even on the Earth, let alone on other worlds in other galaxies, that can realize or instantiate an evolutionary process, whether it be genes, organisms, groups and cultures, seems to cry out for a semantic approach to Darwinism. The theory’s silence on the detailed mechanisms that provide the heredity and the variations in hereditary traits required for evolution here on Earth – nucleic acids and mutations in them – are presumably mechanisms quite different from what we can anticipate finding elsewhere in the universe. This is yet another reason to treat Darwinian theory as a set of models that can be realized in many different ways by many different systems.

Yet a problem remains for the semantic approach, to the theory of natural selection. On the semantic approach a scientific theory is really more than the set of the models that take its name. It’s that set along with the assertion that things in the world realize, satisfy, instantiate, exemplify these definitions sufficiently well to enable us to predict their behavior (observable or unobservable) to some degree of accuracy. Without this further assertion, a
scientific theory is no different from a piece of pure set-theory. So, even the exponent of the semantic theory must recognize that asserting a theory is to make a substantive claim about the world, in particular, it is to say that the same causal process is at work making all these different phenomena satisfy the same definition. Thus, in the end, like the axiomatic account, the semantic approach is committed to the truth of some general claims which themselves cry out for explanation. It is not really enough then to identify a set of models that share a structure in common and are applicable to a diversity of empirical phenomena, and not explain why they do so. Unless we find ourselves at the end of inquiry when no further explanations of the fundamental laws of nature can be given, there will have to be some underlying mechanism or process which is shared among all the different things that realize the same set-theoretical definition, an underlying mechanism which explains
why the predictions we can make employing the model are confirmed. Thus,
the semantic view of theories has all the same intellectual obligations to explain why theories are true or approximately true or at least moving successively closer to the truth than the axiomatic account does. That is, it is also committed to the truth of some substantive general laws about the way things are in the world, laws about natural selection among them. So, in the end it will have to face the problems raised by the role “fitness” plays as the key explanatory variable in Darwinian theory.

http://122.129.75.35/articles/041534316X.pdf

duncan124:
LOL@"We could of course refuse to define fitness. Instead we could just hold, along with realists about theoretical entities, that “fitness” is a theoretical term, like “positive charge” or “atomic mass”.


"Yet a problem remains for the semantic approach..." Hollow Earthers or 'Three ways to make money free loadig scientific ideas and make friends------------------------------>that way.

CoIin: The following overview by Roberta L. Millstein is even clearer. Enjoy!

(The chapter which immediately follows concerns the units of selection and is also fascinating. If anyone is interested, let me know. Apparently "species selection" DOES have its exponents too . )




Tautology and the Nature of Fitness


No summary of the philosophy of evolution would be complete without a discussion
of the “tautology problem,” given the amount of space that has been devoted to it. Yet given a proper understanding of tautology and evolutionary theory, there is neither a prima facie tautology, nor is there a problem. Nonetheless, much interesting philosophical discussion about the nature of fitness has arisen as a result of the misunderstanding.

The “problem” isn’t new, either. According to Hull (1969), evolutionists as far back as Darwin have been defending the theory of natural selection against the criticism that it is tautologous. Nonetheless, the criticism refuses to die, kept alive in large part by creationists who love to quote Popper’s claim that “Darwinism is not a testable scientific theory but a metaphysical research programme” (Popper, 1974, p. 134; italics in original), but who ignore his subsequent recantation (Popper, 1978).

The standard criticism goes as follows: the principle of natural selection is “the
survival of the fittest,” but who are the “fittest”? Those that survive. The principle
then becomes “the survival of those that survive.” Thus, the critics charge, the
theory of natural selection is a tautology, and is therefore circular and empty; it
says nothing about the way the world is, since it is true regardless of the empirical
reality. This claim is often conjoined with the claim that the theory of natural
selection is unfalsifiable – a tautology cannot be proven false. A few technical points regarding the standard criticism – if there is anything wrong with the phrase “the survival of the fittest,” it is that it is an analytic statement, not that it is a tautology, as Sober (1984) points out. A tautology is a statement that is true by virtue of its logical form alone, such as “Either it is raining or it is not raining.” An analytic statement, on the other hand, is a statement that is true by virtue of the meaning of its constituent words (i.e., true by definition), with the classic example being “a bachelor is an unmarried man.” If the phrase “the survival of the fittest” were to be worded as a statement that could be true or false – it is not a statement in its current form – then it would be characterized as an analytic statement rather than a tautology. Still, even as an analytic statement, the critics’ charge that the phrase is circular, empty, and/or unfalsifiable lingers.

One possible line of response to the standard criticism involves a reexamination
of the concept of “fittest.” If the only thing that makes one group of organisms
fitter than another is that the first group in fact survived when the second did not,
then this seems to be the source of the circularity. In response to this concern,
Mills and Beatty (1979) and Brandon (1978) independently developed the propensity interpretation of fitness (although Brandon prefers the term “adaptedness”).
On this view, fitness is not defined in terms of an organism’s actual survival
or reproductive success. Instead, fitness is an organism’s propensity, or ability,
to survive and reproduce in a particular environment. (Fitness is never defined
absolutely, but always relative to a given environment; what enhances survival or
reproductive success in one environment may not do so in a different environment.)
Thus, “the survival of the fittest” is not “the survival of the survivors,” but rather “the survival of those who have the greatest propensity to survive.” The organisms that have the greatest propensity to survive may not in fact survive; consider, for example, two identical twins, one of which is struck by lightening and dies, the other which survives and leaves offspring. Both are equally fit (have the same propensity to survive and reproduce), yet one has greater actual reproductive success. In this manner, the propensity interpretation of fitness attempts to break the purported circularity of the theory of natural selection.

The propensity interpretation of fitness is not without its critics; see, for example
Rosenberg (1982) and Rosenberg and Williams (1986). Even Beatty and Finsen
(née Mills) return to point out some technical difficulties with their own position
(Beatty and Finsen, 1989). Nonetheless, the view enjoys widespread acceptance
among philosophers of biology (see, for example, Burian, 1983; Brandon and
Beatty, 1984; Sober, 1984; Richardson and Burian, 1992). Sober (2000) responds
to Beatty and Finsen’s self-criticisms and points out that whereas the criticisms
apply to the particular mathematical implementation of the propensity interpretation,
they do not challenge the nonmathematical heart of the propensity interpretation.

In spite of the popularity of the propensity interpretation as an account of the
concept of fitness, some philosophers – including Beatty (1992), who has changed
his position on this issue – have argued that it does not actually solve the tautology
problem. Rather, Waters suggests, if we spell out the principle of the survival of the fittest as “Organisms with greater higher fitnesses in (environment) E will probably have greater reproductive success in E than (conspecific) organisms with lower fitnesses” (1986, p. 211), there are two basic ways of interpreting the term “probably”: the propensity interpretation and the frequentist interpretation. Waters argues that if one chooses the propensity interpretation, the principle is true by definition; if one chooses the frequentist interpretation, the principle is not analytic, but it is untestable.

If this argument is correct, does that mean that the theory of evolution is circular
and unfalsifiable? It might, if the phrase “the survival of the fittest” actually described the theory – but it does not. The real problem with the standard criticism is that it misrepresents evolutionary theory, as Hull (1969) and Waters (1986) note. As discussed above, the present-day theory of evolution includes not only natural selection as a possible mechanism leading to the differential survival and reproduction of types; random drift is a possible mechanism, as are migration and mutation. In other words, in any particular case survival may not be “the survival of the fittest.”

Even Darwin’s theory of natural selection alone is not captured by this
phrase;9 as previously mentioned, Darwin described natural selection as a process
requiring

1 a struggle for existence where not all organisms that are born can survive
2 heritable variations between organisms in the population, and
3 variations that confer a differential ability to survive and reproduce.

Whether any or all of these conditions obtain in a particular population is an empirical question, not a matter of definition, and thus we can test the population for the presence or absence of the three conditions. The theory of natural selection is neither circular nor vacuous.

The tautology problem ought to be a dead issue, even if there are those who
refuse to let it go. However, its offspring, the proper conception of fitness, remains
a fruitful area of research (Recent discussions of the concept of fitness in evolutionary theory appear in Biology and Philosophy, volume 6; see also Weber (1996), Stout (1998) and Abrams (1999).

CoIin: Disclaimer : I hereby retract any responsibility for my kangaroo post above on the grounds that it's a load of shite.

Not my finest hour

lori100: Awww....I enjoyed the adventures of Jim and Dave....

CoIin: One source of confusion for me earlier on when contemplating this issue was that if the fitness of organisms is defined purely in terms of their reproductive success (which could only be ascertained by post hoc analysis), then it seems we must either bite the bullet and accept that fitness and survival are defined circularly, and therefore reveal nothing of the way the world works, or else we'd have to claim that that organisms are the explanation for their own fitness!

And that's very silly. That is no explanation at all.

Here's the wrong way to view the scenario:-

Why did Group X survive? Ans: Because they're fit.
And how do we explain their fitness? Ans: Their fitness is explained by their survival.

(And you see that we're going round in circles )


The correct way to look at the issue, I believe, is:-

Why did Group X survive? Ans: Because they're fit.
And how do we explain their fitness? Ans: Their fitness is explained by their forefathers' fitness (with respect to a given environment, of course).

(And the vicious circularity is thereby broken )

But note - a corollary of breaking the circularity is that we no longer enjoy absolute certainty that Group X "won" because they were fit. There's always the possibility of outstanding luck, unnatural intervention, etc.


Let's ask Jimmy the 4x100 relay runner why he's holding that baton:-

"See you, Jimmy. Why are you holding that thing?"

"I'm holding it because I didn't let go of it. So there!"



"Jimmy, try again, please"

"I'm holding it because the previous runner passed it to me."

Good boy, Jimmy.

Now, THAT'S an explanation.

What exactly it is that he's holding is a question for another day. Anyone for Wordy?

Aura: Really, this is what your precious philosophy of science does? Try to define an abstract concept for the sake of a bunch of nitpicking critics who are really just looking for something, anything, to hold against science because they don't like it. Define 'fitness' to a point they would HAVE to accept it, they will find something else to bitch about.
And here I thought time would be spend on interesting and productive things

lori100: uh ohhhh......

CoIin: Why the hostility, Aura?

I'm just trying to think my way to an understanding of the concept from first principles.

Of course, it's not hard to open up a textbook and memorize whatever definition is offered.

But what happens if you're all alone one day? Who does the thinking then?

CoIin: And if you think philosophers of science are anti-science, think again. Au contraire, innit!

Paul Feyerabend may be an exception though

CoIin: As far as I can see, I'm the only person in the Science Forum who actually tries to promote learning. It seem all that other posters want to do is "tell", not "ask".

CrisC: This is also probably worth bringing out. I pulled out a book and did some reading. In 1866, Darwin received a letter from Wallace, the co-discoverer of natural selection. The latter half of the letter reads this:

"I see that he considers your weak point to be that you do not see that 'thought and direction are essential to the action of Natural Selection.' The same objection has been made a score of times by your chief opponents, and I have heard it as often stated myself in conversation. Now, I think this arises almost entirely from your choice of the term Natural Selection, and so constantly comparing it in its effects to man's selection, and also to your so frequently personifying nature as "selecting", as "preferring"..etc, etc. To the few, this is as clear as daylight, and beautifully suggestive, but to many it is evidently a stumbling-block. I wish, therefore, to suggest to you the possibility of entirely avoiding the misconception in your great work and also future editions of 'Origin', and I think it may be done without difficulty and very effectively by adopting Spencer's term..."Survival of the Fittest." This term is a plain expression of the fact, Natural Selection is a metaphorical expression of it."

Darwin did adopt the phrase in order to help more people understand how it works and clear up any confusion.

CoIin: Hi Cris

Yes, I've heard the complaint before that the name "natural selection" is misleading since it suggests "activity".

I suppose natural selection is better thought of as a passive filter than an active chooser.

And if I recall correctly, Wallace and Darvin diverged wildly in later years; Darwin held that natural selection was entirely non-teleological (i.e. devoid of purpose, or "thought and direction" as quoted by you) while Wallace held out hope that "mind" or "intelligence" or the like had some role to play.

Aura: No, I was irked by this...

-The “problem” isn’t new, either. According to Hull (1969), evolutionists as far back as Darwin have been defending the theory of natural selection against the criticism that it is tautologous. Nonetheless, the criticism refuses to die, kept alive in large part by creationists who love to quote Popper’s claim that “Darwinism is not a testable scientific theory but a metaphysical research programme” (Popper, 1974, p. 134; italics in original), but who ignore his subsequent recantation (Popper, 1978).-

an internet forum is one thing, but that serious thinkers are actually bothered enough to spend time to defend against creationists is sad...

duncan124:
Creationists have also been reviewing their ideas and as there are several main religions with creationist activity in them there has been a lot of changes.