I really don't have time to post now, but I'm going to anyway. Van Fraassen writes: "I claim that the success of current scientific theories is no miracle. It is not even surprising to the scientific (Darwinian) mind. For any scientific theory is born into a life of fierce competition, a jungle red in tooth and claw. Only the successful theories survive--the ones which in fact latched on to actual regularities in nature." (Scientific Image, p.40)
James Robert Brown, in "Explaining the Success of Science" (Ratio, 1985) agrees that this Darwinian explanation can account for the first two aspects of success, but not the third:
(1) The sciences "are able to organize and unift a great variety of known phenomena.
(2) This ability to systematize the empirical data is more extensive now than it was for previous theories.
(3) A statistically significant number of novel predictions pan out; that is, our theories get more predictions right than mere guessing would allow." Brown says of (3): "Here the Darwinian analogy breaks down since most species could not survive a radical change of environment, the analogue of a novel prediction."
First a small point: I don't think a novel prediction needs to be analogized to a radical change in environment -- perhaps some should be, but it's not necessary. If an organism can handle living and reproducing in any new environment, i.e., one for which its various features were not historically adapted, then that seems a decent enough analogy to a novel prediction (which makes a prediction different from the cases the thoery was originally designed to handle). A 'radical' change in environment might precipitate a scientific revolution -- i.e., the science (like the organism) might not survive.
Now, a more substantive point, and one which perhaps pushes the analogy farther than is fair. The paleobiologist David Jablonski has shown that genera that are more geographically widespread are more likely to survive mass extinction events (such as the meteor that killed off lots of the dinosaurs). The analogy would be, I suppose, to groups of related theories that 'organize and unify' a greater variety of phenomena -- which are precisely the groups of theories that we (including van Fraassen) count as most successful. So it appears that a van Fraassenite Darwinian has a nice answer to J.R. Brown: viz., the more successful groups of theories will be more likely to deliver novel predictions.
But unfortunately for the van Fraassenite, the biological story doesn't end there. What is strange about Jablonski's results is that a species' being geographically widespread has no statistical correlation with its probability of surviving a mass extinction event. The correlation only appears at the level of genera. (Side note: For the philosophers and biologists who think about group selection, this looks like an instance of it.) So, the analogy would go, the more unifying particular theories do not enjoy any advantage in novel prediction over the less unifying, but the more unifying groups of theories would. Hopefully you can see why I suggested that this may be pushing the analogy too far: I'm not sure there's anything in the domain of science that would correspond nicely to the concepts of genus and species in the evolutionary domain. Although (and now I'm really stretching), if one could be made out, perhaps the structural realists could cash out their notion of structure at the level of the genus, and thereby capture why particular theories come and go, but the structure tends to survive through revolutions.
p.s. -- Can anyone recommend a good article completely devoted to arguing for or against this Darwinian explanation of science's success? I've seen several parts of book chapters or parts of papers dealing with it, but I can't recall seeing a fine-tooth-comb analysis of it.