Survival of the fittest is a tautology

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Claim

Natural selection, or "survival of the fittest," is tautologous (uses circular reasoning) because it says that the fittest individuals leave the most offspring, but it defines those that leave the most offspring as the fittest.

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Responses

  1. "Survival of the fittest" can be a misleading way to think about evolution. Charles Darwin himself adopted the phrase (Herbert Spencer's coinage) only under pressure from Wallace, due to misunderstandings of the phrase "natural selection". Slogans aside, Darwin's point was that heritable variations lead to differential reproductive success.
  2. Natural selection doesn't predict that "the fittest" will survive; rather, it predicts, for instance, that anaerobic bacteria will be more likely to survive than aerobic bacteria in the absence of oxygen. That is, some bacteria have physiologies--independent of any linguistic definition of "fitness"--which make them adaptive to their environment.
  3. If you ask "what caused organism x to survive?" then natural selection tries to answer this question by reference to characteristics of the organism (heritable, behavioral, etc.) relative to its environment (predators, mates, living conditions, etc.). Therefore, the work of a biologist is no different than the work of any other scientist investigating natural causes. Just as there are many causes but only one concept of "causality," so too are there many ways to be fit but only one general concept of "fitness." In fact, all science is based on the axiom that "every effect has a cause." But it would be ridiculous to claim that, since an effect is understood as "that which is caused," therefore science cannot increase our understanding of causality. As long as these investigations yield useful information (about particular causes or particular modes of fitness), then a field of study cannot be logically circular.
  4. Even if the claim were true, that would only mean that it is an obvious fact that "the fittest survive" (sloppily spoken), and this leads to evolution, which was Darwin's point. The creationist argument misses that point. Grabbing one statement out of the whole evolution argument and calling it a tautology is like looking at a mathematical proof where the statement (a+b)*c = a*c + b*c is used, then denouncing the whole proof on the basis that (a+b)*c = a*c + b*c is a tautology. Tautologies are true. Therefore one can draw true conclusions from them. What is wrong with that?
  5. This critique of evolution was addressed at length by Karl Popper. The notion that evolution is reducible to the tautology "survivors survive" attempts to separate evolution from the set of statements which qualify as physical theories. Namely, and in contrast to the response above, all physical theories must have Falsifiability. This is a fancy way of saying that physical theories must be testable by physical experiments and observation. Statements which are true (or false) by definition are not empirically testable. Logic alone dictates the evaluation of such statements. The rub with natural selection and Popper is that what may seem to be tautological is in fact a gloss for the many potentially observable events that lead to the reproductive success of individuals from populations with genetic variation. The view that evolution is tautological is a byproduct of the language used in that gloss. There are clear cut cases, e.g. a Extinction event, in which simple generalizations about the micro-histories of the many individuals in a population are descriptive but they should not be confused with being precisely causal. Lots more here Survival of the fittest.
  6. The phrase "survival of the fittest" is like the title of a chapter in a book: it's not intended to be a single axiom on its face, but a summary of a collection of observable phenomena. By way of comparison, consider "what goes up must come down". Even were someone to throw something into perpetual orbit around the earth (and thus it would never "come down"), gravity would not be disproven, because "what goes up must come down" is not in itself a law or axiom. Moreover, the fit do not always survive in a local context, just as a wrench tossed into space won't always "come down". All that is required is that the fit tend towards surviving long enough to reproduce offspring that may carry whatever characteristic the fit may have had that tended to allow survival in a given environment. Thus, it's not so much a tautology as it is a statistical tendency that, over time, selects for suitability to environment, where "survival to offspring bearing status in a given environment" is used as the test of "suitability to that environment".
  7. "Tautology" does not mean "circular reasoning". The claim can't decide what accusation it wants to bring against evolution, apparently. Circular reasoning is a logical fallacy. Tautology is not. Tautologies are trivially true. The reasoning is not circular.
  8. According to the tautological argument, the fittest are those who survive, and the survivors are deemed 'the fittest'. Yet, no biologist would seriously believe that those that survive are always the fittest, or that the fittest always survive. It's trivially obvious that 'the fittest' can and do die. "Survival of the fittest" is a merely simplified version of the observation that, in nature, the fittest tend to survive *more frequently* than the unfit. For example, let's assume we have a species of animals and divide them into two groups: the fit and the unfit. Further, let's say that all of the "fit" organisms are genetically identical, and all the "unfit" organisms are genetically identical (thus removing the argument that I did a bad job of picking which organisms go into which group). Let's say that 50% of the 'fit' organisms die before reaching maturity, but 75% of the 'unfit' organisms die before reaching maturity. This case confirms the idea that the fit tend to survive more frequently than the unfit, and illustrates the point that "the fit" and "the survivors" are not identical groups -- half of the 'fit' organisms died early, and 25% of the unfit organisms survived. Similarly, let's assume we have two rabbits identical in every way except that one rabbit can run faster than the other. Since the ability to run is important for the survival of rabbits, we would say that the faster rabbit is more fit - and therefore, more likely to survive. However, if the faster rabbit happens to get an infection and dies, we do not simply say that the slower rabbit *must* have been more fit to survive because it survived when the faster rabbit didn't. We maintain our original idea that the faster rabbit was more fit, but that *in general* the fittest organisms tend to survive more frequently than the unfit. The argument that "survival of the fittest is a tautology" claims that evolutionists believe that "the fittest" and "survivors" are identical groups (evolutionists don't believe that), and that evolutionists have no way to judge fitness other than survival (which is false). From a definitional standpoint, "fitness" means possessing traits which aid in survival, which is correlated with (but not identical to) survival itself.
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Fallacies contained in this claim

External Links

  • Wilkins, John, 1997. Evolution and philosophy: A good tautology is hard to find. [4]
  • Lindsay, Don, 1997. Is "Survival Of The Fittest" A Tautology? [5]

References

  1. Anon., n.d. Alpheus Hyatt (1838-1902). [6]
  2. Hyatt, Alpheus, 1866. On the paralellism between the different stages of life in the individual and those in the entire group of the molluscous order Tetrabranchiata. Mem. Boston Soc. Nat. History 1:193-209
  3. Weiner, Jonathan, 1995. The Beak of the Finch, Knopf.

Further Reading

  • Pigliucci, Massimo, 2004, Did Popper Refute Evolution? Skeptical Inquirer, Vol. 28, No.5, p.15

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Acknowledgments

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