From an old email exchange…
Here’s the brief summary of Darwin’s theory (from The Origin of Species – I believe).
- If there are organisms that reproduce, and
- If offspring inherit traits from their parents(s), and
- If there is variability of traits, and
- If the environment limits the size of natural populations,
- Then those members of the population with maladaptive traits (as determined by the environment) will die out or reproduce less, and
- 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.