Natural selection as tautology

From an old email exchange…

Here’s the brief summary of Darwin’s theory (from The Origin of Species – I believe).

  1. If there are organisms that reproduce, and
  2. If offspring inherit traits from their parents(s), and
  3. If there is variability of traits, and
  4. If the environment limits the size of natural populations,
  5. Then those members of the population with maladaptive traits (as determined by the environment) will die out or reproduce less, and
  6. Then those members with adaptive traits (as determined by the environment) will survive to reproduction or reproduce more.

To falsify this you have to assume that premises 1-4 are true and show that 5 or 6 are false. Take proposition 5, for instance. You would have to find members of the population with “maladaptive traits” (whatever those are) who don’t die out or reproduce less. From these definitions alone that seems impossible to me, since if the individuals don’t die or reduce their reproduction, then you can just say that they didn’t really have maladaptive traits. I suggested, therefore, that the theory gives names to things that are observed and that it doesn’t make predictions. You could also show that the theory doesn’t talk about reality as we know it, i.e. the premises (again propositions 1-4) aren’t true, but that seems as difficult.

Apparently Popper said something about how actually it’s not a tautology, or at worst is a useful tautology. I have no idea where. Obviously the interest comes from the likes of fossil records, phylogenetic trees, genetics, etc: perhaps that’s where the tautology disappears.



  1. tom

    On useful tautologies: Maths is tautology. It makes predictions.

    Separate: is there a useful distinction between the process of evolution (a tautology) and the evidence of evolution (i.e. that it actually happened on earth, that it was responsible for speciation, etc)?

  2. Andy

    I agree with mathematics being a useful tautology. Some blurb on that on my other blog:

    Miller makes the assumption that since a conclusion of a deductive inference is “implicitly or explicitly” included within its premises, that nothing new is discovered by drawing the conclusion. Every deductive argument, says Miller, is “question begging”. This is easily defeated with an mathematical example. Given some set of axioms, e.g. good old Dedekind-Peano arithmetic, it is insanely difficult to prove anything that’s not trivially true. In fact many trivially true statements are difficult to prove! Drawing “question begging” inferences can be tricky and informative.

    Perhaps speciation is the way forward. I do think that if Dawkins concentrated on this, with evidence – he claims to be a scientist, doesn’t he? – then he’d be much more productive with the intelligent design crowd. But then focusing on speciation isn’t as sexy as claiming (as I claim he does) that the process of evolution is worthy as a system of metaphysics.

  3. Donald Stahl

    I was under the impression that the charge of tautology was well-known to evolutionists, and that they considered it not a serious problem. I seem to recall a book comparing evolution and “just-so stories” every now and then. BTW, information (clarification?) on (what I assume to be) the British genre of “just-so stories” would be appreciated.

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