Jerry Fodor and Nikolaas Tinbergen

[Reg_Prescott]

The environment is real. There are causal forces that impact survival and continued abiity to reproduce. That's the force at work. Your difficulty seems semantic. Selection is a metaphor, and so I reckon there are always ways for a metaphor to be misconstrued, and teleology to be erroneously dragged in. The same can be said for "force," I would imagine. Or "pressure," another word oft used. As in "coal soot on the trees in Birmingham exerted a selective pressure on the moth species...."

You, the one I admire most.

Let's suppose all my friends died of cancer.

Was there selection pressure on them?


After all, I'm pretty sure the environment was real and impinged upon them.

In my humble opinion, with your "selection" (see how easily it falls between scare quotes?) talk, you are saying nothing at all.

All my friends succumbed to natural Grim Reaper selection?

Any bloody rubbish can be described this way!!

Sigh!
Could it be described that way?

Is there anything that could NOT be described that way?

[Forest_Dump]

As to whether selection was at work with regards to your friends succumbing to cancer, the answer is an obvious yes if they died before having children. If they didn't have children those people were definitely selected against relative to those whodid, had more or had more who were in turn able to survive to breeding age. If your friends died in their 80s or later, then maybe we wouldn't call it an exampe ofnatural selection.

But as noted, the real question does seem to be your grasp of semantics and metaphor. Let me try a slight change to your complaint above:

In obeying the law of gravity, water selects the path of least resistence when flowing down a hill. Is there a problem here? Do you believe it is all wrong because you assumeI am saying 1) water obeys anything; 2) there are such things as laws made and enforced by a law-maker; 3) water consciously selects a path?

Would you say Newton invented gravity?

[Reg_Prescott]

As to whether selection was at work with regards to your friends succumbing to cancer, the answer is an obvious yes if they died before having children. If they didn't have children those people were definitely selected against relative to those whodid, had more or had more who were in turn able to survive to breeding age. If your friends died in their 80s or later, then maybe we wouldn't call it an exampe ofnatural selection.

But as noted, the real question does seem to be your grasp of semantics and metaphor. Let me try a slight change to your complaint above:

In obeying the law of gravity, water selects the path of least resistence when flowing down a hill. Is there a problem here? Do you believe it is all wrong because you assumeI am saying 1) water obeys anything; 2) there are such things as laws made and enforced by a law-maker; 3) water consciously selects a path?

Would you say Newton invented gravity?

Ignoring the usual condescension....


Well, Forest, don't you see? Any old rubbish could be described in the idiom of selection if you're that way inclined. I'm not. I feel it's explanatorily vacuous, a bit like Moliere's "opium puts you to sleep because it has a dormitive virtue".

Did Newton invent gravity?

I'd say it depends what you mean by the term. You're probably waiting to invite me to defenestrate myself from an 11th floor window, Haha!

Is gravity an attractive force that acts instantaneously over any distance against a backdrop of absolute space and absolute time? -- as it would be if Newtonian physics was construed realistically.

No one believes that any more. Do you?

So in that respect, yes, he made it up.

(in my worthless opinion)

[Forest_Dump]

I do need to be very aware of the effects of gravity. Understanding gravity helps explain sedimentation and stratigraphy and, where I live and work, changes in slope, etc., due to isostatic rebound is key to understanding changes in lake levels and the paths of rivers. Nonetheless, when you get down to it, my understanding of gravity doesn't even need to be as precise as Newton's.

On the other hand, while I do find an understanding of natural selection as Darwin defined it is extremely useful but certainly Dawkins (and Dennett as well as many others) offer much more powerful ideas that are of even greater value. However, I too have issues with Dawkins and Dennett (and certainly Darwin's work from almost 200 years ago) in that I do not see naturalselection as having the ability to explain everything that happened in the past. I think that fo some topics such as human evolutionary history, other evolutionary forces were much more imprtant.

That being said, however, I also believe it is important to remember that when we stand on the shoulders of giants it is best to refrain from peeing on their heads. Untold thousands of scientists and philosophers have learned incredible amounts in the last 150 to 200 years but there is no doubt in my mind that Darwin's contribution stands as among the most important in the history of science.

[doogles]

I've just tuned into this thread.

Reg_Prescott seems to be making the point that a process of 'Natural Selection' cannot occur because Nature cannot ACTIVELY select anything. In my opinion, he is pedantically correct in that statement. But as several posters have pointed out, the term is used somewhat metaphorically, and the problem is not one of 'concept' but of semantics.

I like to look at basics. Let's look at it from another simple perspective. I hope it fits into the common sense level of discussion along the lines Wolfhnd referred to early in the thread.

Let's accept that a range of modifications and mutations of genomes occurs regularly within all, or most, species. Hyksos says that he has produced computer simulations of such (Re: Jerry Fodor and Nikolaas Tinbergen by hyksos on Sat Jul 08, 2017 4:14 am).

If those modified genes are expressed as altered manifestations in phenotype (eg white polar bears) or in hormone secretions (personality or behaviour), doesn't it then become a question of whether any new manifestation of gene expression provides nil, negative or positive advantages over its own or other species within the micro- or macro environment in which the species exists?

If so, it then becomes a case of ENVIRONMENTAL SUITABILITY for the manifestation of the modified or mutated gene. As I said earlier, the new manifestation may be a handicap, may be irrelevant, or may provide an advantage over its own or other species. Obviously in the case of its own species, isolation of a new variety that is fit, fitter or the fittest to survive in a particular environment may result in gene modifications over time that make it unsuitable for sexual reproduction with older varieties of the species, and then we can say that a new species has evolved.

It all depends on the ENVIRONMENTAL SUITABILITY for the manifestations of altered genomes.

It's a PASSIVE occurrence, dependent on the chance modifications of genes and the state of nature (micro- or macro-environment) in which the genome modifications happen. In one way, we could say that the natural environment determines which changes are unfit, fit, or the fittest to survive in any given area. Maybe we could still keep calling this stage of the interaction 'NATURAL SELECTION'.

We don't have to, of course; we could say that "evolutionary processes depend on the environmental suitability for manifestations of gene modifications to survive better than others".

'NATURAL SELECTION' is easier, and suffices, so long as we understand what those two words imply.

[Reg_Prescott]

I've just tuned into this thread.

Reg_Prescott seems to be making the point that a process of 'Natural Selection' cannot occur because Nature cannot ACTIVELY select anything. In my opinion, he is pedantically correct in that statement. But as several posters have pointed out, the term is used somewhat metaphorically, and the problem is not one of 'concept' but of semantics.

Thank you for that thoughtful post, Doogles.

This is not quite the point I was making, though it's possible I was confused again.

Now, let's get binary. Either natural selection is real or not.

If it's real, maybe it does some selecting, like a good bridge player.

"Scuse me while I do some selecting" - Mother nature

But I thought we agreed Mother Nature has no mind?

And if it's a pedantic metaphor.... pedantic metaphors cause nothing, right?

Furthermore, our bridge competition could be described in selectional terms if you like.

"Those who play best tend to get selected and make it into the next round"

I still think it's a load of shite,

Haha!

But I might be wrong.

[Reg_Prescott]

My Mum plays bridge for Scotland, by the way.

if that helps.

[doogles]

Thank you Reg_Prescott for the response. You suggested "Now, let's get binary. Either natural selection is real or not." That statement appeared to require an answer.

My BINARY answer is definitely "No!".

I affirmed this in my previous post. I will affirm it again and again and again if I am asked the same question from anybody who insists that I interpret their question PEDANTICALLY AS IT IS FRAMED, in a binary fashion. But only if that person insists on a binary answer, and who does not allow me to request a re-framing of their question to avoid any misunderstanding.

For anybody who wishes a balanced (as distinct from binary) answer to the question of the use of the term "Natural Selection' to explain evolution, please read my previous post.

I congratulate your mum for 'playing bridge for Scotland', Reg_Prescott, by the way. You must be proud of her.

[PaulN]

And if it's a pedantic metaphor.... pedantic metaphors cause nothing, right?

Metaphors can describe conditions that do cause.

You seem to confuse the linguistic act of naming with the actual causes that are referred to by the blanket term.

[PaulN]

Metaphors are successful at description.... that's why we use them so much.

[Reg_Prescott]

Metaphors are successful at description.... that's why we use them so much.

Quite so. I'm not averse to a useful fiction any more than the next man.

But point masses and ideal gases have no causal powers. On the grounds they are not real.

This is the point I was trying to impress the hot chicks with.

[Reg_Prescott]

I can't hang around. I've been invited to dinner by the average American family.

[hyksos]

"Well, then", I continue, "If it's not Mother Nature doing the selecting, what is?

This is likely to induce a little squirming. Just a few days ago on another site I was told that it is actually mathematics that does the selecting!!

I am going to assume many things about this interaction you had on "another site", since I wasn't there.

(I will assume that) this person on the other site said something along the lines of : the word "Selection" is standing in as a placeholder for a complex statistical process.

More on that topic here : viewtopic.php?f=37&t=35052

[Reg_Prescott]

@ Hyksos (re post directly above)

I think the remarks inside the boxed text that you've posted above are exactly right.

The problem is, though, as I see things at least, yourself and whoever wrote the text seem to regard this as a vindication of natural selection theory. On the contrary, I see it as a demonstration of natural selection's explanatory vacuity.

Depending on how fitness is defined, all talk of "survival of the fittest" -- natural selection in a nutshell -- expresses either a flat-out vacuous truism ("the survivors survive"), or if one attempts to escape the circularity by endorsing a propensity interpretation of fitness, it tends towards a vacuous truism.

The latter case is exactly analogous to "the casino wins" or "those who have what it takes to survive and reproduce will tend to survive and reproduce"; not true in every individual case (sometimes these purple-haired grannies get lucky, and sometimes an Adonis-like pre-pubescent lion gets struck by lightning), yet cannot fail to be true given a long enough time and large enough numbers.

In both cases, the writer of the text is absolutely right: these are mathematical or linguistic "truisms" that "cannot be subverted" (his/her own words).

So what, you might retort?

1. One does not need to leave one's armchair to establish the truth of a truism. Why, then, do I keep hearing that natural selection is an empirical theory that has survived test after test? That which cannot be subverted does not need to be tested.

2. A truism explains precisely nothing. (cf. "Why is Peter a bachelor?" Ans "Because all bachelors are unmarried men") Why, then, do I keep hearing of the prodigious explanatory power of natural selection theory?

[PaulN]

Because its explanatory power lies not in the obvious fact that selection happens, but rather in HOW traits can effect the survival and fertility of an organism. And that's where empirical approach comes in. Black moths live longer in Birmingham's bad old smog era, because we observe that predatory fowl pass over them and miss them, thanks to the moths coloration matching the sooty trees. Thus the trait is selected for, as those dark moths reproduce while the pale moths become some bird's lunch.

In other words, we learn something specific about how the environment imposes certain stresses on a population which will favor a certain shift in allele frequency. It's the observed reality of such mechanisms, not some semantic ritual, which gives the theory its value. As you rightly point out, real science doesn't happen in the armchair.

[Reg_Prescott]

Because its explanatory power lies not in the obvious fact that selection happens, but rather in HOW traits can effect the survival and fertility of an organism. And that's where empirical approach comes in. Black moths live longer in Birmingham's bad old smog era, because we observe that predatory fowl pass over them and miss them, thanks to the moths coloration matching the sooty trees. Thus the trait is selected for, as those dark moths reproduce while the pale moths become some bird's lunch.

In other words, we learn something specific about how the environment imposes certain stresses on a population which will favor a certain shift in allele frequency. It's the observed reality of such mechanisms, not some semantic ritual, which gives the theory its value. As you rightly point out, real science doesn't happen in the armchair.

The problem here, Paul, as I see things, is that in cases such as those celebrated peppered moths, you are being deceived into believing that what does the explaining is the principle of natural selection (PNS). I would suggest, on the other hand, that what does the explaining are the facts of each individual case.

Let's assume that the principle "people die when their time is up" (PDTU) is a vacuous truism, and thus lacks any explanatory power.

Let's also examine three dudes who died recently: Tom, Dick and Harry, say. I would suggest that precisely nothing is explained by appealing to a vacuous general schema such as PDTU. What would do the explaining, instead, is the idiosyncratic facts pertinent to each particular kicking-of-the-bucket: cancer, syphilis, tortoise falling on the head, etc.

Now, I've been arguing above that PNS is also a vacuous truism, expressed something like "those organisms possessing traits advantageous to survival and reproduction will tend to survive and reproduce more successfully than those without".

Granting its truistic non-empirical vacuity, it appears to me that PNS enjoys the same degree of explanatory power as PDTU, viz., none whatsoever.

[Reg_Prescott]

If that wasn't clear enough...

What was the question again? What explains the increase in black moth numbers?

My answer: (inter alia) Their blackness.

Protest: "You mean it wasn't a vacuous truism that explains it?"

[Positor]

Now, I've been arguing above that PNS is also a vacuous truism, expressed something like "those organisms possessing traits advantageous to survival and reproduction will tend to survive and reproduce more successfully than those without".

But this says nothing about how species evolve. For that, you need to mention mutations, and explain how random mutations give rise to non-random changes in species. It then ceases to be a truism, and becomes far from obvious. Other explanations seem plausible if one is ignorant of the science, e.g. Lamarckism or creationism.

If natural 'selection' (or whatever you prefer to call it) is so obvious, it seems odd that virtually no-one believed it, or even thought of it, before Darwin. If it is a truism, it follows that Paley's watchmaker argument (with which it is incompatible) is the denial of a truism, i.e. it is a logical impossibility. But that does not seem right; the 'argument from design' may be false but it is not illogical.

[Reg_Prescott]

Now, I've been arguing above that PNS is also a vacuous truism, expressed something like "those organisms possessing traits advantageous to survival and reproduction will tend to survive and reproduce more successfully than those without".

But this says nothing about how species evolve. For that, you need to mention mutations, and explain how random mutations give rise to non-random changes in species. It then ceases to be a truism, and becomes far from obvious. Other explanations seem plausible if one is ignorant of the science, e.g. Lamarckism or creationism.

If natural 'selection' (or whatever you prefer to call it) is so obvious, it seems odd that virtually no-one believed it, or even thought of it, before Darwin. If it is a truism, it follows that Paley's watchmaker argument (with which it is incompatible) is the denial of a truism, i.e. it is a logical impossibility. But that does not seem right; the 'argument from design' may be false but it is not illogical.

Was it Herbert Spencer who said? Or Huxley? when he first heard of Darwin's theory...


"How terribly foolish of me not to have thought of that"

And why? Why would that have been said if it's not a well-cloaked truism? Which is what I think it is. Isn't a true scientist supposed to say "Hmm, it's an interesting idea, but it will need to be tested"?

Did anyone ever say to Einstein "How terribly foolish of me not to have thought of that relativity stuff"?

Why not? Because it's not a vacuous truism.

In my opinion.

Always delighted to hear your thoughts, Positor.

Positor, I always respect your input, and I'm glad to see you again.

[Reg_Prescott]

.

If natural 'selection' (or whatever you prefer to call it) is so obvious, it seems odd that virtually no-one believed it, or even thought of it, before Darwin. If it is a truism, it follows that Paley's watchmaker argument (with which it is incompatible) is the denial of a truism, i.e. it is a logical impossibility. But that does not seem right; the 'argument from design' may be false but it is not illogical.

Seems like a non-sequitur to me.

Paley's argument was "if you see something that looks designed then it probably is designed" or whatever.

It might be a good or bad argument, but I see nothing tautological in it.

[hyksos]

Depending on how fitness is defined, all talk of "survival of the fittest" -- natural selection in a nutshell -- expresses either a flat-out vacuous truism ("the survivors survive"),

That is not natural selection in a nutshell, at all.

This is what the Theory of Evolution by Natural Selection looks like in a nutshell.

:: In a population of reproducing entities that contain variation, under certain conditions that variation will increase. In rare conditions, the variation will increase so much that speciation occurs. ::

The occurrence of speciation is not a guarantee. The theory only claims that it does occur in some situations. The crucial claim the theory makes about the world is what is written between the double semicolons. I am using "crucial claim" in a highly technical sense here, as it usually appears in grand theories of physics.

or if one attempts to escape the circularity by endorsing a propensity interpretation of fitness, it tends towards a vacuous truism.

.. or one could attempt to escape this circularity by stating the actual theory.

The latter case is exactly analogous to "the casino wins" or "those who have what it takes to survive and reproduce will tend to survive and reproduce"; not true in every individual case (sometimes these purple-haired grannies get lucky, and sometimes an Adonis-like pre-pubescent lion gets struck by lightning), yet cannot fail to be true given a long enough time and large enough numbers.

The rest of this is based off a mischaracterisation of the theory, so I won't respond to it.

In both cases, the writer of the text is absolutely right: these are mathematical or linguistic "truisms" that "cannot be subverted" (his/her own words).

So what, you might retort?

1. One does not need to leave one's armchair to establish the truth of a truism. Why, then, do I keep hearing that natural selection is an empirical theory that has survived test after test? That which cannot be subverted does not need to be tested.

You have lost track of the conversation you started with an unknown conversant on an unknown forum. The claim made by that nameless person on far-away forum was that the english word "Selection" does not imply a conscious act of discrimination by a Selector Entity. The anonymous person claimed that mathematics or statistics is doing the selection of traits seen in extant species. If the anonymous poster claimed such, then I agree with him. As I said above the english word "selection" is standing in for a complex statistical process.

2. A truism explains precisely nothing. (cf. "Why is Peter a bachelor?" Ans "Because all bachelors are unmarried men") Why, then, do I keep hearing of the prodigious explanatory power of natural selection theory?

Statistical processes are truisms, yes.

However, as I wrote above, Natural Selection makes a claim about states-of-affairs in the world. That claim is testable. This is why it is a theory and why it requires experimental corroboration.

[Forest_Dump]

Sometimes if you insist on only looking at it as a simplistic truism, then a simplistic truism is all you get. And that might be why it took so long for someone to look a little closer and get more out of it. I think Reg doesn't get it and so he doesn't get more out of it. Populations are not composed of individuals who are all the same - there is variation. And some ofthat variation sometimes makes some individuals a little better at surviving and having offspring. Others on the less fortunate end of the sprectrum of variability become more likely to get selected against. So, sometimes "the survivors are the ones who survive" overlooks that the "average" will shift over time i.e., the range of variation doesn't stay static over time. So, we might look at the fossils of horses over a few tens of millions of years and wonder why they started off small and got bigger over time. Reg might want to say "they just did". Others might want to say "because God planned it that way" or "because there is some kind of inherent tendency for horses to get bigger over time". With the theory of evolution by way of natural selection youcan take another look at the context of the fossils and perhaps identify a selective pressure where smaller horse are selected against while bigger horses are selected for. That does make it testable.

[hyksos]

I wanted to edit parts of that post, but the one-hour cutoff.

Reg_P's nutshell has many historical roots, and I was being disingenuous by being so harsh on it. I would have edited out the harshness, but the forum mechanics stopped me.

Depending on how fitness is defined, all talk of "survival of the fittest" -- natural selection in a nutshell -- expresses either a flat-out vacuous truism ("the survivors survive"),

"Survival of the fittest" was some kind of phrase that came out of a British Sociologist who was dabbling in eugenics. There was an idea in the late victorian era, that human beings could be "bred" like dogs and livestock for preferred traits. This idea was so appealing that eugenicists believed that they could not only use it to cure disease -- but it could be used to cure crime. Taking it even further, used to eliminate poverty. You eliminate poverty by "letting the poor die off" or some such idea, as if poverty were a phenotypic trait transmitted by genes to sons and daughters.

Wallace actually liked the phrase "survival of the fittest" a lot. If Reg_Prescott is here to attack the biologists who swirled around the beginnings of the theory, then he has a good point. There were many gaping holes and errors near the theory's historical beginnings.

On the other hand, if he seeks to characterize the theory on legal terms by equivocating the theory with these early historical ... metaphors , that is not an honest way to proceed.

[Forest_Dump]

Truth be told I think I was thrown by the odd terminology of "theory" of natural selection. I never refer to it that way and can't recall seeing anyone else do so. I usually describe natural selection as a force or mechanism so even Reg's description as a truism doesn't cause me any problems. Natural selection does work as one mechanism or force to help explain evolution and so for this reason is included within evolutionary theory. But of course, in some cases, so does gravity in some ways in explaining why bird flight or swim bladders evolved. However, I do agree with Reg in that it is not always or perhaps even often testable. But it is sometimes and sometimesit is a useful mechanism to look at and think about. It is certainly more believable than Intelligent Designers, etc. But I depart from Dawkins and Dennett in thinking that for some topics, natural selection may not be the most important explanatory factor. Some times I think gene flow, the founder effect even pure blind luck or chance might be more important.

[hyksos]

Truth be told I think I was thrown by the odd terminology of "theory" of natural selection. I never refer to it that way and can't recall seeing anyone else do so. I usually describe natural selection as a force or mechanism so even Reg's description as a truism doesn't cause me any problems. Natural selection does work as one mechanism or force to help explain evolution and so for this reason is included within evolutionary theory. But of course, in some cases, so does gravity in some ways in explaining why bird flight or swim bladders evolved. However, I do agree with Reg in that it is not always or perhaps even often testable. But it is sometimes and sometimesit is a useful mechanism to look at and think about. It is certainly more believable than Intelligent Designers, etc. But I depart from Dawkins and Dennett in thinking that for some topics, natural selection may not be the most important explanatory factor. Some times I think gene flow, the founder effect even pure blind luck or chance might be more important.

Yes. I would need to re-edit a bunch of posts I made in this thread.

I tend to use Natural Selection as a placeholder for the idea that animals and plants are products of wholey natural processes. That claim is almost dis attached from any theory (as you point out). Darwin himself only concocted the phrase to mirror "Artificial Selection" performed on native plants to increase their utility as food crops.

Contemporary Biologists use a third definition. They use a legal definition where N-S is one out of many mechanisms that underlie Evolution. For example, if hybridism is a mode of speciation (and it is), then we don't say that the "environment did that." A hybrid species that is between a leopard and a jaguar is not the product of some kind of "selection" of its traits.

[Reg_Prescott]

That is not natural selection in a nutshell, at all.

.. or one could attempt to escape this circularity by stating the actual theory.

The rest of this is based off a mischaracterisation of the theory, so I won't respond to it.

etc., etc.

Well, if my own misgivings expressed above can be dismissed as a simple mischaracterization of the theory, and there is no circularity, one can only wonder why so much ink has been spilled over the so-called "tautology problem", i.e., circularity, or the risk thereof, in natural selection which Darwin himself encapsulated in the maxim "survival of the fittest".

For an overview of the conceptual confusions, and entire imbroglio in general, I'd refer you to Mills and Beatty's "The Propensity Interpretation of Fitness"

http://pdfs.semanticscholar.org/1480/f6 ... a8910e.pdf

Theirs is an attempt to wriggle out of the vicious circularity of defining fitness in terms of actual survival and reproductive success by proposing that it be defined instead as a propensity to survive and reproduce successfully.

For reasons mentioned in a post above, I feel their attempt fails. Instead of a flat-out vacuous truism we end up asymptotically approaching a vacuous truism.

In order to escape the circularity entirely, fitness would have to be defined in such a manner as to make no reference whatsoever to survival and reproduction. To my knowledge, no one has ever done so -- and for obvious reasons. Fitness, if regarded as a quality inherent within organisms themselves, as opposed to their reproductive success, is what we might call multiply realizable. That is to say a certain trait advantageous to one organism in one ecology might be disadvantageous to another organism in a different, or even the same, environment.

"Survival of the fittest" was some kind of phrase that came out of a British Sociologist who was dabbling in eugenics. There was an idea in the late victorian era, that human beings could be "bred" like dogs and livestock for preferred traits. This idea was so appealing that eugenicists believed that they could not only use it to cure disease -- but it could be used to cure crime. Taking it even further, used to eliminate poverty. You eliminate poverty by "letting the poor die off" or some such idea, as if poverty were a phenotypic trait transmitted by genes to sons and daughters.

Perhaps so. Darwin may not have coined the phrase, though he apparently regarded it as felicitous enough in capturing his theory of natural selection as to incorporate it himself in later writings.

[Reg_Prescott]

As for how natural selection ought to be characterised, I quote the following from the Stanford Encyclopedia of Philosophy:

(and as for those who can't recall natural selection being referred to as a "theory", a quick google search might do the trick. Prepare for a deluge!)


"Natural selection is a causal process. Distinguishing it from other processes in evolution is one of major conceptual and empirical problems of evolutionary biology. The bare bones of Darwin's theory of evolution by natural selection are elegantly simple. Typically (but not necessarily) there is variation among organisms within a reproducing population. Oftentimes (but not always) this variation is (to some degree) heritable. When this variation is causally connected to differential ability to survive and reproduce, differential reproduction will probably ensue. This last claim is one way of stating the Principle of Natural Selection (from here on PNS). The PNS goes beyond the causally neutral statement that is sometimes listed as the third of what are often called “Darwin's Three Conditions”, viz., different variants sometimes reproduce at different rates. That statement leaves open the question of whether or not the variation in question is causally responsible for the differential reproduction. It leaves open the question of whether a qualitatively similar outcome would result from repeated iterations of this set-up. It leaves open the question of whether this process is natural selection or drift (see below). It—the causally neutral statement—does not suffice to state Darwin's causal theory. Darwin clearly recognized this (see, for example 1871) as did Lewontin (1978); although many contemporary commentators fail to see this.

Why is it that some variants leave more offspring than others? In those cases we label natural selection, it is because those variants are better adapted, or are fitter than their competitors. Thus we can define natural selection as follows: Natural selection is differential reproduction due to differential fitness (or differential adaptedness) within a common selective environment (see next section). This definition makes the concept of natural selection dependent on that of fitness, which is unfortunate since many philosophers find the concept of fitness deeply mysterious (see e.g., Ariew and Lewontin 2004). But like it or not, that is the way the theory is structured. And, fortunately, we can make considerable headway in understanding natural selection without solving all of the philosophical problems surrounding the concept of fitness."


I've highlighted the critical section in bold.

"Natural selection is differential reproduction due to differential fitness". In other words, the more fit reproduce more successfully than the less fit.

But who exactly are the more fit? If the answer is "those who reproduce more successfully" then we have an obvious tautology, i.e., "those who reproduce more successfully do so more successfully than those who reproduce less successfully".

This is the source of the tautology problem, and this is why a propensity interpretation of fitness has been suggested. But as noted above, it seems to me the propensity interpretation helps little if at all in escaping the circularity.

[Positor]

"Natural selection is differential reproduction due to differential fitness". In other words, the more fit reproduce more successfully than the less fit.

But who exactly are the more fit? If the answer is "those who reproduce more successfully" then we have an obvious tautology, i.e., "those who reproduce more successfully do so more successfully than those who reproduce less successfully".

Agreed. But suppose we say: "The fit are those who are able to live longer, on average, in a given environment".

They reproduce more successfully because they live longer on average.
It is not the case that they live longer on average because they reproduce more successfully.

In other words:

They reproduce more successfully because they are more fit.
It is not the case that they are more fit because they reproduce more successfully.

[PaulN]

The usefulness of NS theory doesn't lie in the concept of fitness, but in the specifics of what is adaptation. When you look at actual observations, the vacuity dissolves away and you see how specific forces in an environment drive living organisms towards variations that accommodate those forces. And when you get concrete and specific, you can make predictions which are testable. If philosophers grasp the power of predictions, then the concept of "fitness" doesn't have to be "deeply mysterious."

Testable prediction: where food supply becomes very limited for a species A, which is isolated from areas with more food by geographic factors, smaller body size will be favored. I.e. selected for.

This prediction was tested and borne out by many discoveries in the fossil record, and is now called insular dwarfism. It has been found recently in the genus Homo. See also the Channel Island fox, or the dwarf elephants of Crete.

[Reg_Prescott]

Testable prediction: where food supply becomes very limited for a species A, which is isolated from areas with more food by geographic factors, smaller body size will be favored. I.e. selected for.

This prediction was tested and borne out by many discoveries in the fossil record, and is now called insular dwarfism. It has been found recently in the genus Homo. See also the Channel Island fox, or the dwarf elephants of Crete.

Er, is this part of the theory of natural selection?

Or just common sense?


Either way, I was corrected for mischaracterizing the theory by Hyksos, and chastised for "not getting it" by Forrest.

I see nothing in Hyksos's correct characterization that mentions body size.

My own theory predicts those who lack the dosh to pay for a pizza will got less pizza than those who have the greenbacks.

Testable too.