Evolution and Philosophy: Tautology

Summary: It is claimed that "survival of the fittest" is an empty tautology because the fittest are defined as "those that survive", leaving us with the circular "survival of those that survive". Far from being empty – this part of Darwin's theory makes substantive, repeatable and testable predictions about events in the real world.

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urvival of the fittest (SoF) is testable

Creationists commonly formulate the Tautology argument somewhat as follows: The Theory of evolution is built around the phrase "Survival of the Fittest" (SoF), but since the only measure of "fitness" is the survival rate, this phrase actually reduces to "Survival of the survivors" which is circular and thus an empty tautology. However, on examining this argument we see that it is an attack only against the wording used to describe one of the core concepts in evolution. It is not a challenge to the observable phenomenon to which SoF actually refers.

SoF refers to the fact that given a certain selective regime in the real world, a population will tend to evolve in the same direction over and over, and we can often predict in advance what the response will be. For example, black moths will increase in frequency if trees are dark, and gray moths will increase in frequency if trees are covered in gray lichen. It isn't just "whatever survives survives"; it is that particular traits are preserved depending on environment. Thus SoF isn't empty wording, it is a description of events in the real world.

While this summarizes the core of the argument, owing principally to the many possible meanings of "tautology" this discussion is often seen in alternative forms, raising a variety of different issues, which are touched on in the following.

Historical introduction to the tautology argument

The tautology argument grew out of a change made by Darwin between the fourth ^[1] and fifth ^[2] editions of his "On the Origin of Species". He changed the title of the fourth chapter from "NATURAL SELECTION" to "NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST." (SoF) He wrote: "This preservation of favourable variations, and the destruction of injurious variations, I call Natural Selection, or the Survival of the Fittest." and thereafter used the two terms as synonyms.

In 1879 Samuel Butler ^[3] charged that natural selection is a "truism", leading to a focus on the phrase SoF and the assertion that because survival rates define fitness, "'fittest' has no force" and thus natural selection and hence the whole of the theory of evolution explains nothing.

Here, note that an attack launched against the phrase SoF immediately incorporates its synonym "Natural Selection", despite the obvious fact that selection by nature is no more tautological than selection by man. Thereafter, as usual, the attack is widened to include all of evolution.

A current version of the tautology critique

A recent version of the tautology argument was made by Ann Coulter who said:

"The second prong of Darwin's "theory" is generally nothing but a circular statement: Through the process of natural selection, the "fittest" survive. Who are the "fittest"? The ones who survive! Why look – it happens every time! The "survival of the fittest" would be a joke if it weren't part of the belief system of a fanatical cult infesting the Scientific Community. The beauty of having a scientific theory that's a tautology is that it can't be disproved."^[4]

Most creationists agree that the fittest survive

Note that the foregoing 'argument' characterizes as a "joke" the idea that it is the best adapted (fittest) parents who have most offspring. So what do creationists propose as an alternative? – that it is the worst adapted who are most fertile; that it is the arctic fox with the shortest fur who fathers the most pups generation after generation?

No, apparently not, Coulter like many other fundamentalists, accepts that such adaptation occurs, but denies that adaptation below the level of species (microevolution) is really evolution. She says:

"Natural selection has never been demonstrated to change anything fancier than the shape of a bird's beak."^[5]

"Evolution is not the capacity of bacteria to develop antibiotic resistance, but which never evolves into anything but more bacteria. Evolution is not the phenomenon of an existing species changing over the course of may years for example."^[6]

But this reveals a contradiction. SoF refers to only one element of evolution, not the entire theory. SoF refers to no aspect of "macroevolution"; not to the creation of new species, or to the tree of common descent generated by speciation, or the nested hierarchy of characteristics within that tree; nor does it refer to mutations as the cause of variation. While supposing that Coulter, like many creationists, believes that all characteristics are preloaded into the genome by design she also clearly knows that species do change in response to changes in their environment. But such changes (like beak shape in response to varying circumstances) are precisely the part of evolution that SoF describes! So why are creationists arguing that a position they already accept is a "joke"? Could it be they don't understand their own argument?

Survival due to specific characteristics

Coulter's argument asks: `Who are the "fittest"? The ones who survive!', apparently a variant of "survival of the survivors", but it is not abstract individuals who survive, but individuals with specific heritable characteristics. These characteristics cause improved survival in predicable and often testable ways.

Specific heritable characteristics may include:

visual sensitivity to yellow
densest fur
longest tail feathers

There is simply nothing tautological (in the circular sense) about survival of long tail feathers. That "fitness" is intended to refer to specific characteristics is the core to understanding that SoF is not in any sense a tautology, because by observation we can, for example, establish that those arctic foxes with the densest fur survive to pass on that characteristic. Similarly in a changing environment we may note that in dry years it is the finches with the strongest beaks that survive, while in wet years those with the longest beaks are retained. Hence, instances of SoF are clearly observationally contingent, and repeated failures to see the obvious, would disprove SoF.

Sometimes survival isn't determined by fitness

Another problem with Coulter's argument is that it sets up full equivalence between survival and fitness. "Who are the "fittest"? The ones who survive! Why look – it happens every time!"(emphasis added). If that were true, then all differential survival would necessarily be selection. But we have a name for differential survival that isn't selection; it is called drift (basically, changes in a population's gene pool due to chance). And in fact we can often perform tests that distinguish selection from drift. We couldn't do that if selection were just "those that survive survive".

We now briefly examine two aspects of tautologies themselves.

Are all tautologies necessarily true?

Asking if tautologies are necessarily true may seem ridiculous, after all, isn't that the definition of a tautology? In fact there are a number of definitions. Two common formulations are:

Semantic: redundancy or saying the same thing twice (which can be dated to 1581 ^[7]).
examples: The gift is free; Her wet nose is moist.

Logic: a statement that is necessarily true due to its form.
examples: Socrates is mortal or he is not; Husbands are married men.

Looking at these two formulations we immediately note a key difference. Saying the same thing twice, if the repeated statement is false can't be necessarily true. Hence the semantic and logic forms are not equivalent.

The quote from Coulter begins by describing SoF as a "circular statement" an apparent reference to the semantic meaning, but ends by stating that tautologies "can't be disproved" presumably referring to the definition in logic. This makes about as much sense as saying that a nocturnal mammal that catches flying insects using echo location is the bat which I use for hitting baseballs. This is definition switching. Does Coulter believe bad puns can discredit evolutionary theory?

Mathematical expressions of scientific laws as tautologies

In population genetics SoF is represented mathematically. Therein we see a formal variable called fitness (W) which is measured by the proportion of a trait that survives into the next generation. The simplest form of the equation looks like this:

W_abs = N_after/N_before

where:
W_abs is absolute fitness
N_before is the Number of individuals with some genotype in a first generation (before selection)
N_after is the Number of individuals with that genotype in the following generation (after selection)

Some philosophers have stated that mathematical expressions are tautologies. For example Russel said: 'Pure mathematics consists of tautologies, analogous to "men are men," but usually more complicated.'^[8] While noting that Russel limited his statement to pure mathematics some may wish to insist that Wabs = N_after/N_before (and consequently SoF) is a tautology, since it refers to the same idea expressed in two different forms. If so, then every mathematical expression containing a single equal sign between two sets of equivalent expressions must also be a tautology. This must therefore include Newton's F=ma and Einstein's E=mc².

The above examples highlight the fact that some statements which may be formally defined as tautologies are substantive, not empty since they accurately describe real world events.

The tautology argument is an attack against wording, not substance.

The argument against "Survival of the Fittest" as a tautology is directed against the formulation of that phrase, not the theory it describes. Darwin had previously been attacked for the words "Natural Selection" when used to summarize his central idea. In reply he wrote:

Others have objected that the term selection implies conscious choice in the animals which become modified; and it has even been urged that, as plants have no volition, natural selection is not applicable to them! In the literal sense of the word, no doubt, natural selection is a misnomer; but who ever objected to chemists speaking of the elective affinities of the various elements? – and yet an acid cannot strictly be said to elect the base with which it will in preference combine. It has been said that I speak of natural selection as an active power or Deity; but who objects to an author speaking of the attraction of gravity as ruling the movements of the planets? Every one knows what is meant and is implied by such metaphorical expressions; and they are almost necessary for brevity.^[9]

So it seems entirely possible that Darwin would have agreed that SoF is, in the literal sense, a "misnomer" or "false phrase", but he well knew that it is simply a descriptive label or suggestive summary referring to one part of his theory.

Summary points:

Survival of the Fittest (SoF) does not include many key aspects of evolution, like common descent, the nested hierarchy, mutations, or speciation. What SoF does include is accepted by most creationists as part of "microevolution". So why are they attacking a part of evolution many of them agree with?
In SoF, fitness cannot be equivalent to survival because characteristics generated by drift also survive, thus SoF cannot be a tautology.
SoF was intended to be a synonym for Natural Selection (NS), but NS is clearly not a tautology.
SoF is a descriptive label referring to part of Darwin's theory. Attacking the label does not challenge the theory itself.
Semantic and logical tautologies are substantially different. Switching from the semantic to the logic definition in mid argument produces incoherent nonsense.
SoF (expressed as Wabs = N_after/N_before) is a tautology only in the same sense that F=ma and E=mc² are tautologies.
Fitness refers to specific characteristics, not some abstract and unknown generality, and so can be tested against the real world in the same way m in F=ma can be checked. There is nothing tautological about survival of the longest fur, longest tail feathers, or most bark-like coloration.
SoF generates results that can often predict future events in the real world, such as the results of further experiments, and is therefore not empty words.

Acknowledgements:

‡ This article was composed with valuable help and comments from:
John S. Wilkins; El Cid; Ivar Ylvisaker; Ernest Major; Burkhard; Ron Okimoto; Iain Inkster; J.J. Lodder; David Hare-Scott; Steven L.; and others

References:

[1] Darwin, Charles, 1866. "ON THE ORIGIN OF SPECIES", Fourth Edition. London, John Murray, pp. 90
[2] Darwin, Charles, 1869. "ON THE ORIGIN OF SPECIES", Fifth Edition. London, John Murray, pp. 91
[3] Butler, Samuel, 1879 "Evolution, Old and New", Hardwicke And Bogue pp. 351
(first use must have been earlier since Darwin's colleague Alfred Russel Wallace was defending against the charge in 1873.)
[4] Coulter, Ann, 2007. "Godless: The Church of Liberalism". Random House Inc. pp. 212-213, ISBN 978-1-4000-5421-3
[5] Ibid., pp. 209.
[6] Ibid., pp. 202.
[7] FULKE, WILLIAM, 1581. "A Defense of the Sincere and True Translations of the Holy Scriptures into the English tongue", pp. 382.
("...they contain not a ridiculous tautology or vain repetition" is one of many uses of tautology as repetition in this work.)
[8] Russell, Bertrand, 1946. "History of western philosophy". George Allen & Unwin Ltd. pp. 153, ISBN 0-415-32505-6
[9] Darwin, 1866., pp. 91-92.

Revision note:

† The original 1997 version of this faq is here.