Yes of course “survival of the fittest” is tautological!

If one phrase could be said to have percolated into popular consciousness as summing up Darwin’s theory of natural selection, that phrase would be “survival of the fittest”. Which is rather a pity since that phrase is not how scientists state the principles of Darwinism. That’s because the phrase is tautological.

In Darwinian terms “fitness” is the ability to survive and reproduce. As stated by H. Allen Orr: “In the crudest terms, fitness involves the ability of organism … to survive and reproduce in the environment in which they find themselves”.1

Given that “fitness” is the tendency to survive and reproduce then, obviously, it is the fittest who tend to survive and reproduce. The maxim “survival of the fittest” is thus a tautology.

And boy has that caused problems!    Not, I might add, problems for biologists, but problems for some who comment on biology, from creationists to philosophers of science. I had been under the impression that all this had been clarified decades ago, but on reading the article on biological fitness in the Stanford Encyclopedia of Philosophy, written in 2015 by Alex Rosenberg and Frederic Bouchard, I was surprised to find that this is still a live issue among philosophers.

The worry is that, if the phrase “survival of the fittest” is tautological, then perhaps the whole concept of Darwinian “fitness” is tautological and thus empty of any actual content, and then maybe the whole of Darwinism becomes “metaphysics” rather than science. This accusation has been made by creationists, and even by luminaries such as Sir Karl Popper.

The reply is actually quite simple: Yes, the phrase “survival of the fittest” is tautological; but no, the concept of “fitness” is not tautological, and nor is Darwinian natural selection. That’s it; that’s the resolution of the “problem”.

Darwinian “fitness” is simply an accounting of how likely an animal is to leave descendants. If a particular trait — say bigger antlers, greater swiftness, or a better sense of smell — tends to result in an animal leaving more descendants, then the trait has greater “fitness”. There is nothing tautological about that concept.

Now let’s suppose that animals differ in their traits (which is a known fact; deer of a given species do differ in antler size, et cetera), and further, let’s suppose that traits tend to be passed to an animal’s descendants. Thus a trait bestowing greater fitness can be passed on to offspring who thereby also have greater fitness (this inheritance of genetic traits is also a known fact).

Under those conditions “natural selection” occurs. The “natural” here means “automatically”, or “logically/tautologically entailed” by the above conditions. If those conditions hold then Darwinian evolution occurs.

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That is the essence of Darwinism, as stated in all the textbooks.2   But, in the above, I did not make any statement about the “survival of the fittest”. That’s because that phrase is a mere tautology, already entailed in the definition of “fitness”.

But it is only that phrase that is tautological; there is nothing tautological about the concept of “fitness”, nor about natural selection. The phrase “survival of the fittest” is not part of a formal statement of Darwinism for that reason: it is a redundant phrase that adds nothing.

And, since it is not part of a formal statement of Darwinism, the fact that it is tautological carries no implication that Darwinian evolution itself is tautological. If one takes three information-containing sentences and adds a tautology, then the combination of the four is not tautological, since the combination has the information content of the first three sentences!

Indeed, the phrase “survival of the fittest” was not part of Darwin’s Origin of Species until the fifth edition. It was added on the advice of Herbert Spencer and Alfred Wallace, who thought that it would help people to understand natural selection. Well, maybe it does. Pointing out a tautology can sometimes help people understand (for example, maths teachers spend their lives pointing out tautologies to their pupils). But one should not mistake that phrase for the actual Darwinian theory itself.

Sadly, exactly that mistake has caused problems ever since Popper initiated it. So many people now associate the phrase “survival of the fittest” with Darwinism that many consider it essential to rescue the phrase from being a tautology.

The Stanford article by Rosenberg and Bouchard says:

Darwin’s theory of natural selection provides an explanation of all three of these features of the biological realm … by explaining the process of “the survival of the fittest.”

This mistakenly places the phrase “survival of the fittest” at the centre of Darwinian logic. The article continues by saying:

[Darwinian theory’s] … reliance on the concept of `fitness’ makes it imperative that conceptual problems threatening the explanatory legitimacy of this notion be solved.

After failing to resolve the “conceptual problems” they end the article with:

As these debates suggest, far from being merely a 19th century slogan, understanding the meaning of the “survival of the fittest” is of philosophical and biological urgency.

Philosophical and biological urgency? Wow, sounds important! And yet the answer is easy and obvious: “Survival of the fittest” is a tautology. Sorted!    Rosenberg and Bouchard are confusing that one phrase for the concept “fitness” itself. They are mistaking Spencer’s commentary on Darwin’s theory for Darwin’s theory.

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Suppose that we define “speed” as the distance travelled divided by the time taken. That is not tautological. But suppose I then add a comment: “objects with a higher speed travel further in a given time”. Given the definition of “speed” that comment is tautological. But my adding a tautological comment does not make the concept “speed” itself tautological!

I feel like I’m belabouring a very obvious point, but such a blunder is exactly what many philosophers from Popper to Rosenberg and Bouchard have committed. They seem to regard the phrase “survival of the fittest” as sufficiently primary that they need it to be non-tautological. And so they try to achieve that by trying to find another account of “fitness” under which “survival of the fittest” is true but not tautological.

For example, Rosenberg and Bouchard explicitly ask for a redefinition of “fitness”, in order to rescue “survival of the fittest”, when they say:

It appears therefore that evolutionary theory requires a definition of fitness that will protect it from the charges of tautology, triviality, unfalsifiability, and consequent explanatory infirmity. If no such definition is in fact forthcoming, then what is required by the theory’s adherents is an alternative account of its structure and content or its role in the research program of biology.

This is akin to trying to find another definition of “speed” such that the phrase “objects with a higher speed travel further in a given time” is no longer tautological but still true. This is an utterly misguided and hopeless quest based on mistaking the status of the phrase “survival of the fittest” in the first place.

Of course biologists doing their day jobs have never let this issue worry them: they intuitively know that there is nothing wrong with the concept of “fitness”, and if one particular phrase is tautological then so what?

I confess to being baffled that this argument is still “live” in philosophical circles. The resolution I’ve given above is not new, indeed all of it was said by Dawkins decades ago in his book The Extended Phenotype (the relevant chapter, “An agony in five fits”, is online here and is well worth reading).

And yet, since then, many have tried to come up with convoluted analyses of the concept “fitness”, all to try to rescue the phrase “survival of the fittest”, all to avoid acknowledging that that one phrase is indeed a mere tautology (whether usefully illustrative or not).3    Yet it does not matter, since it is merely Spencer’s commentary on Darwin’s theory of natural selection, not a statement of the theory itself.

Notes:

[1] The technical definitions of “fitness” get more intricate since likelihood of surviving and reproducing is always a probability, and thus to evaluate the “fitness” of a trait one needs to average over populations; the Orr article deals with such complications.

[2] An influential statement of the principles of Darwinism was by Richard Lewontin in 1970 (from “The Units of Selection”, Annual Review of Ecology and Systematics, quoted from here). Note the absence of any “survival of the fittest” statement, since it would be superfluous.

“As seen by present-day evolutionists, Darwin’s scheme embodies three principles …

1. Different individuals in a population have different morphologies, physiologies, and behaviors (phenotypic variation).

2. Different phenotypes have different rates of survival and reproduction in different environments (differential fitness).

3. There is a correlation between parents and offspring in the contribution of each to future generations (fitness is heritable).

These three principles embody the principle of evolution by natural selection. While they hold, a population will undergo evolutionary change.”

[3] Attempts to analyse “fitness” in such a way as to prevent “survival of the fittest” being tautological include this well-known one by Gould, called Darwin’s Untimely Burial. Many others have taken a similar line, including Massimo Pigliucci, Eric Scully, Jason Rosenhouse, and Tam Hunt. As I see it, all of these are misguided.

In contrast, recent clear statements of why there is no problem to solve include those by Fred Leavitt and Sedeer El-Showk.

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14 thoughts on “Yes of course “survival of the fittest” is tautological!

  1. Damian Trasler

    I think there’s a fundamental error here, drawing an equality between biological term definitions and lexicography.
    My understanding (from the point of view of a playwright, not a biologist) was that “fittest” was being used in the sense of “The most ideal for the situation”. The finches that developed different beaks, for example – the ones that prospered were those whose beaks were the “fittest” for the food stuffs available. The biggest issue I’ve always had is the general interpretation that “fittest” means most athletically prepared.
    Apologies if this is repeating tired old stuff. I like your posts, but I don’t seem to be thinking very hard today.

    Reply
    1. Coel Post author

      … “fittest” was being used in the sense of “The most ideal for the situation”.

      Yes, true. But the only test of what is “ideal” is whether it helps the animal survive and reproduce. Thus, ultimately, “fitness” is defined in terms of survival/reproduction, and then from there one can work out, empirically, what things make the animal “fit”.

    2. Damian Trasler

      Yes, I see that. But it’s still a useful comparison – Survival of the fittest for their environment instead of survival of those created to exist there.
      Must go and refuel my brain. Can’t word today.

  2. Mark Wallace

    “Darwinian “fitness” is simply an accounting of how likely an animal is to leave descendants.”

    I don’t really see how you can jump straight into reproduction and descendants. I had a similar understanding as Damian, I think: that fitness is more related to aptitude for obtaining food, enduring climate, avoiding predators, etc. in a particular setting. The importance of the idea is in allowing the study of specific traits in relation to specific natural circumstances. It’s obvious that a tendency to survive longer when a certain trait is present will lead to greater chances for reproduction, but that skips out the interesting part of the theory.

    Your approach does seem tautological in that it’s completely post hoc: count the number of descendants and then decide by comparing the numbers if they were fit or not. But an animal could be wiped out by a freak occurence – a meteor, let’s say – and still have been absolutely fit within its natural environment.

    Reply
    1. Coel Post author

      Hi Mark,

      I had a similar understanding as Damian, I think: that fitness is more related to aptitude for obtaining food, enduring climate, avoiding predators, etc. in a particular setting.

      But how did you arrive at that list of attributes? (Why do you regard “avoiding predators” as “fit” and not “getting eaten”?) The answer is that those are things that lead to survival and reproduction. So you define the concept “fitness” in terms of survival and reproduction, and then one can ask which attributes amount to “fitness”. However, one cannot assess “fitness” except, ultimately, in terms of what leads to survival and reproduction.

      But an animal could be wiped out by a freak occurence – a meteor, let’s say – and still have been absolutely fit within its natural environment.

      Yes, that sort of freak occurrence can occur, which is why one needs to take a probabilistic account of “fitness”, averaging over populations. One can also say that such an animal had high “fitness” for the meteor-less environment, but not for the meteor-containing environment.

    2. Mark Wallace

      “So you define the concept “fitness” in terms of survival and reproduction, and then one can ask which attributes amount to “fitness”.”

      When you say you define the concept thusly, you mean *you* do, but Darwin didn’t – he observed species at work in their environment, and noted how they had adapted to it. He used a lot of induction; you seem to use none. You begin by an assumption that continued existence has to be explained Darwinianly, rather than allowing for all sorts of extraneous non-Darwinian factors (e.g. meteors). The problems are clearer when you think of it in terms of humanity. Indians reproduce more than Europeans – should we understand that by concluding that Indians are biologically fitter? People who don’t have children don’t reproduce at all (another tautology) – are they biologically unfit?

    3. Coel Post author

      When you say you define the concept thusly, you mean *you* do, …

      And most of modern biology!

      … but Darwin didn’t – he observed species at work in their environment, and noted how they had adapted to it.

      Yes, true. But the concept “fitness” is really just a measure of how successful that adaptation is.

      Indians reproduce more than Europeans – should we understand that by concluding that Indians are biologically fitter?

      In terms of biological “fitness”, yes. That follows from the definition of the concept. E.g. from wiki: “[fitness] is equal to the average contribution to the gene pool of the next generation that is made by an average individual of the specified genotype or phenotype.”

      People who don’t have children don’t reproduce at all (another tautology) – are they biologically unfit?

      One can’t really define “fitness” for an individual (see the definition just given), but if a given genotype or phenotype leaves fewer descendants then, yes, they are less “fit” by the very definition of Darwinian “fitness”.

    4. Mark Wallace

      I feel you’re contradicting yourself here. You admit your definition isn’t Darwin’s, then go on to say it is “Darwinian”. Is Darwin not Darwinian, then?

    5. Coel Post author

      “Darwinian theory” has been developed and refined a lot since Darwin. How the theory is stated nowadays is often different from how Darwin stated things. In the same way, what we call “Newton’s Laws” today are rather different from how Newton stated things.

      Nowadays the concept of “Darwinian fitness” is defined in terms of how many descendants you have.

  3. Rich Edwards (cabbagesofdoom)

    You make some good points about tautologies in general but I think you get fitness a little wrong here. “Survival of the fittest” is either a tautology AND WRONG, or not a tautology and right. If it is survival of the fittest individual then it is somewhat of a tautology, although misses the importance of heredity. Fitness applies to variable heritable traits – almost universally “genes” – not individuals. It is possible to be the “fittest” individual for purely environmental reasons, such as a good diet making one big and strong. That will not result in natural selection. Likewise, the fittest traits can fail to be passed on if random events overpower them – the essence of random genetic drift. So the REAL “survival of the fittest [heritable variable traits]” is NOT a tautology (if I understand the word correctly) as it need not be true. However, when it IS true, it is a condition under which natural selection will inevitably occur. The causal link between the heritability and the fitness is critical.

    Reply
    1. Coel Post author

      Hi Rich, I agree with many of your qualifications, but these are mostly accounted for by defining “fitness” in terms of averages over populations.

  4. Philosopher Eric

    Yes Coel, if we define “fittest” as “that which survives,” then “Survival of the fittest” is certainly tautological, though perhaps useful nonetheless. I agree that Darwinian natural selection itself, however, happens to be a non tautological theory. I’m not surprised that this would be disputed in the philosophy community however, given that the term “dispute” does seem to sum the field up pretty well.

    Nevertheless I am quite surprised that you’ve placed our mutual friend Massimo Pigliucci, on a list of professionals who believe that “survival of the fittest” must be made non tautological in order to preserve the concept of Darwinian natural selection! The story you linked to under his name suggests that he has the utmost respect for Darwinian evolution, and beyond any existing tautologies. In it he was merely skeptical that the survival of human pop culture should be described as “Darwinian.” (I do of course agree. The evolution of life seems very different from the evolution of our fads.)

    So why have you included Massimo Pigliucci, on this particular list?

    Reply
    1. Coel Post author

      Hi Eric,

      So why have you included Massimo Pigliucci, on this particular list?

      I’ve put Massimo on the list since he has always resisted accepting that “survival of the fittest” is tautological (if you’re aware of anywhere where he has stated that it is, can you point me to it?). As I interpret him, he is saying that it is not tautological since we can obtain independent information on what makes an animal “fitter” (and then he worries that, in the cultural case, we cannot do so, and thus run the risk of tautologies). I don’t agree with him on either part of that.

  5. Pingback: Once more on theory and law in science | coelsblog

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