"There is always a philosophy for lack of courage."—Albert Camus

Friday, December 02, 2005

The Evolutionary Tautology

A commenter on our ID post directed us to this supposed refutation of Karl Popper's arguement that the notion of survival of the fittest is a tautology.

The argument posits the following important premise:

This ["survival of the fittest"] is not a tautology, or, if it is, then so is the Newtonian equation F=ma [Sober 1984, chapter 2], which is the basis for a lot of ordinary physical explanation.

That is not true, however, for the two propositions are most definitely not identical in type. The Newtonian equation is a proposition that cannot be untrue; there is no alternative possibility that would explain the relationship between force, mass, and acceleration that we observe. There are, however, other possible explanations for the origin and variety of species. Just as two and two must equal four if the cosmos is to hold together, so must force, mass, and acceleration be related as Newton suggested. For the species we see on the earth to exist, however, Darwinian evolution is not a necessity, as the author of the article admits:

Recently, there have been attacks on the very notion of adaptive explanation by some evolutionary biologists themselves (eg, Gould and Lewontin [1979]). These fall into two camps - those who think adaptation is not enough to explain diversity of form, and those who think that adaptive explanations require more information than one can obtain from either reverse engineering or the ability to generate plausible scenarios. The reason given for the former is a kind of argument from incredulity - natural selection is not thought to be a sufficient cause, and that macroevolution (evolution at or above the level of species) is a process of a different kind than selection within species. Arguments about parsimony (Ockham's Razor) abound.

Darwinian natural selection is the preferred explanation of a great many people, but that is greatly different from it being a necessary proposition. And that is why it can correctly be classified as a tautology, as Popper did.

17 comments:

Matt Huisman said...

Nice follow up, STK.

I've always found it interesting that the when pressed to define what 'fittest' might mean, the natural selection crowd always point to reproduction levels as being a defining characteristic.

If that's the case, should I read anything into the fact that these same people tend to be among the lowest reproducing members of society?

(By the way, after yesterday's conversation - you'll be happy to know that I enjoyed a fine Chicago-style hot dog for lunch today - no papaya juice anywhere in sight.)

Macht said...

Survival of the fittest doesn't mean that the fittest [i]do[/i] survive, it means the fittest [i]tend[/i] to survive. So they aren't equal to each other and there is something else that comes into the equation.

But even if we grant that it is a tautology and even if evolution isn't true and all species were specially created, then survival of the fittest still seems to be true. If, for example, I have a low sperm count or I'm incredibly ugly or I have a chemical in my brain that makes me takes stupid risks, then I and people like me are going to tend to not reproduce as much as people who aren't like me in those respects (this doesn't mean people with low sperm counts won't reproduce, it just means it is less likely that they will). So even if evolution is false and survival of the fittest is a tautology, survival of the fittest still seems to be true.

The Classic Liberal Anonymous said...

I don't understand how the introduction of statistics into the definition changes the tautology argument?

So its the likely survival of those who are most likely to survive.

Is this fundamentally different than merely survival of the fittest?

James Elliott said...

Not when you put it like that. But then you putting it like that is sophistry, so there you go.

The Classic Liberal Anonymous said...

You're wrong on who is guilty of sophistry, James. Look to the man who injected the statistics into the argument; that was not me.

S. T. Karnick said...

Matt, I think that those who have regular access to Chicago-style hot dogs may not be the fittest to survive, but we enjoy survival the most.

Hunter Baker said...

James, sometimes I think people are making substantive points when you call them on sophistry. Could you give me your definition of that word?

Macht said...

I don't think it's sophistry, but I do think that it is a mistake to think that fitness is defined solely as those who survive. Let's say that we have two species, one who produces plenty of offspring and easily survives from generation and another species who barely produces enough offspring to get by. In this case, the former seems to be best suited to its environment even though both species survive. So defining fitness as equal to survival seems wrong. Like I said above, the fact that fitness tends to lead to survival doesn't imply that fitness is survival.

I see "survival of the fittest" as a non-issue. It seems to be true whether Darwinian evolution is true or not. The bigger issue (and the issue that I think most people really have in mind when the bring up the tautology argument) is how increased fitness can be generated by evolution. I think this is what the original post has a problem with, too, when it says "There are, however, other possible explanations for the origin and variety of species" and "natural selection is not thought to be a sufficient cause, and that macroevolution (evolution at or above the level of species) is a process of a different kind than selection within species." Both of these seem to be suggesting that evolution can't account for increased levels of fitness. But neither of those objections seem to say anything about the notion of survival of the fittest.

James Elliott said...

Why, the very definition of sophistry all of you delineated in a conversation I took no part in: Semantics. Don't cry to me when your definitions bite you in the behind.

Ed Darrell said...

I've never heard any biologist propose that reproduction was the measure of fitness. Can anyone point me to such a claim?

Did any of you ever take more than high school biology? I'd wager that your questions would be answered nicely in a well-done treatment of evolution, either academic or popular. Have you read Weiner's book, The Beak of the Finch? Or Mayr's What Evolution Is?

Ed Darrell said...

Fitness is almost always described as the ability to gather food and avoid predation.

Matt Huisman said...

Here's a quote from PBS (item #8):

"Survival of the fittest usually makes one think of the biggest, strongest, or smartest individuals being the winners, but in a biological sense, evolutionary fitness refers to the ability to survive and reproduce in a particular environment. Popular interpretations of "survival of the fittest" typically ignore the importance of both reproduction and cooperation. To survive but not pass on one's genes to the next generation is to be biologically unfit."

Matt Huisman said...

I should follow that up by asking what good is it (from an evolutionary standpoint) to be successful at gathering food and avoiding predators if you don't reproduce (and reproduce at levels that surpass those of the weak)?

The reproductive dominance of the 'fit' genes is the whole game in evolution - which is why it is often cited as the measure of fitness.

Ed Darrell said...

That definition does not make the passing of the genes the fitness definition, Matt. My complaint is that the tautology is one invented to make a problem, and not one that is proposed by evolution.

Consider a concrete example: Modifications of the skin to produce means of surviving cold, say by fur or by feathers: How is such fitness a tautology?

Sure, the feathered one must pass the genes along. But the passing of the genes is secondary to the fitness mechanism at best, and not part of it. Feathers have nothing intrinsic to do with reproduction.

Is this misunderstanding of evolution intentional? I don't know. But philosophers who argue that the tiger's survival strategy is reproduction come off sounding rather ill-informed about the birds and the bees.

I've always found it bizarre that people misread biology and biologists that way. "The ability to survive" is the first part of that phrase that comes closest to the claim made here, but in order to make the tautology, one would have to ignore that clause completely.

This is why biology is done best by biologists watching God's creation, and not by philosophers pontificating on what God should have done.

Matt Huisman said...

Consider a concrete example: Modifications of the skin to produce means of surviving cold, say by fur or by feathers: How is such fitness a tautology?

How did you determine that the change from skin to feathers was advantageous and therefore worthy of selection? You start at the end and say, hmm, looks like those with feathers were the ones that survived over time - I'll bet those feathers were helpful because...

In other words, you define fitness by what is successful - which is a tautology.

But the passing of the genes is secondary to the fitness mechanism at best, and not part of it. Feathers have nothing intrinsic to do with reproduction.

The problem is the entire evolutionary model is based on the survival (and eventual dominance) of advantageous genes/traits over multiple generations. You had previously defined fitness as survival, and when you consider survival over many generations, reproduction is the indicator of survival/success.

Ed Darrell said...

The problem is that all of life is dependent on survival. But that's not the definitional difficulty you started talking about.

Evolution could be tautology, if survival was not dependent on anything other than surviving, if survival was dependent solely on chance, for example. But that's not the way life works. Faster antelope outrun the American cheetah, and they survive to pass their genes along. It's worth noting that the genes that made that individual faster (if there was a genetic component) are also passed along, so the next generation from the loins of the surviving antelope will be genetically more "fit" to survive than the last. It wasn't "survival" that got the genes passed, it was speed. So if you think speed is survival, you're right.

But you've got to distort the definition of both speed and survival to make that work.

It is true that we can look at what makes an organism fit only retrospectively in nature. I picked feathers because they are not involved in reproduction directly. Your original proposal for a tautology involved only reproduction. Please don't try to fog what little clarity is available.

To be certain, reproductive excess can be a survival technique. Coral produce millions of eggs, and in the course of things most of them will be devoured by other critters. Coral survival depends on there being so many polyps eventually that not all of them can be consumed. That's just one feature, however, and it's not the reproductive strategy for most of our more obvious examples, such as great apes, herding ungulates, or most birds.

The difficulty comes when you confuse the measure of success with the means of success. Sure, a faster antelope survives, and after a thousand generations, it's only the faster ones who survived. Survival is the measure of success; but it was speed that made the survival possible.

Same with the feathers. There is a classic piece in literature about sparrows caught in a freak, pre-season freeze. Many died -- but those with the thickest feathers survived the freeze to breed again. Were evolution a tautology, the freeze would have made no difference in which birds survived -- those with thin insulation would have done as well as those with thick insulation, and "survival" would have been the only possible measure.

But time and again we see that feathers do count in who survives and who doesn't.

Here's another truism of science: Those who do not understand evolution will resort to logical and semantic tricks instead of relying on the evidence. So let's consider real examples, and give you a chance to indicate that the tautology argument doesn't fit this truism.

We cut the roots on our largest oak tree this spring, part of work to fix the foundation of our house. Probably because of this stress, it produced a more copious than usual crop of acorns (stressed trees often bear more fruit), especially in comparison with its siblings and children who were not so stressed. According to the tautology, the stressing must have magically made the tree somehow more "fit," since its reproductive rate rose so dramatically.

Is that really what you wish to argue?

Can you provide a serious example of a creature whose survivability depends solely on survival, without any means of distinguishing which individuals of the species might be more successful than others?

Matt Huisman said...

It is true that we can look at what makes an organism fit only retrospectively in nature. I picked feathers because they are not involved in reproduction directly. Your original proposal for a tautology involved only reproduction. Please don't try to fog what little clarity is available.

Since we can only look at what makes an organism fit retroactively, what we are doing is looking to see how reproduction was affected by the fitness traits (feathers, speed, etc.) that you have mentioned. The problem I have with evolutionary theory is not that there are fitness traits that may be behind a given change - the problem is that you can only define what these traits are by the reproductive results.

What is fitness? Fitness is the sum of the traits of that which has survived. What survived? That which was fit.

Are darker moths more objectively fit than lighter ones? No, they're just better fit for their specific circumstance. Is speed always more fit? Sure, as long as nothing else (strength, cooperation, endurance, etc.) is sacrificed in order to attain it. Otherwise, I could make a case that it could be an occaisional hindrance. In other words, these fitness traits are too situationally specific to really mean anything.

And we haven't even touched on the wild guesses that Darwinian's make regarding how certain features were developed - with no apparent intermediate necessity - over time. The point is that no matter what set of facts are presented to it, evolution always has room - it can never be proven wrong.

None of this would matter if Darwinian's didn't use this study to make ultimate truth claims. But they invariably do - and at that point it is fair to point out some of evolution's limitations.