Dave Jarvis offers an interesting variant of the suboptimality anti-design argument at http://joot.com/dave/writings/articles/design.shtml. His variant is based on the recent finding that mammals under certain conditions can regenerate organs previously thought unregenerable. I responded to this line of objection in The Design Revolution, chapter 6 (“Optimal Design”). Here is a relevant portion of that chapter:
Just because a design could be improved in the sense increasing the functionality of some aspect of an organism does not mean that such an improvement would be beneficial within the wider ecosystem within which the organism finds itself. A functionality belonging to a predator might be vastly improvable, but also might render the predator that much more dangerous to its prey and thereby drastically alter the balance of the ecosystem, conceivably to the detriment of the entire ecosystem. In criticizing design, biologists tend to place a premium on functionalities of individual organisms and see design as optimal to the degree that those individual functionalities are maximized. But higher order designs of entire ecosystems might require lower order designs of individual organisms to fall short of maximal function.
Our view of design is shaped too much by sports competitions. We always want to go faster, higher, longer, and stronger. But do we really want to go faster, higher, longer, and stronger without limit? Of course not. It is precisely the limits on functionalities that make the game of life interesting (thatÃ¢â‚¬â„¢s why many games employ handicaps). A five-hundred-pound seven-foot-six football player with the strength of a gorilla and the speed of a cheetah would instantly be banned from the sport, because just by playing the game to the best of oneÃ¢â‚¬â„¢s ability, such a player would maim or kill all normal players who got in the way.
Fans might show up for the novelty or out of bloodlust, but such a player would destroy the competitive drama of the game. Indeed, before long this super-player would destroy or run off anyone willing to play the game and there would cease to be a game. Likewise, such a predator in an ecosystem would wipe out all the prey, after which it would go extinct. Or if the super-creature was omnivorous, it would reproduce optimally (like rabbits? like bacteria?) until it wiped out all life, after which it would again go extinct (unless it became an autotroph and could manufacture its food from scratch as some single-celled organisms).
Biology is among other things a drama. For dramas to be interesting requires characters who are less than optimal in some respects. In fact, authors of human dramas often consciously design their characters with flaws and weaknesses. Would Hamlet be nearly as interesting a play if Shakespeare had not designed the playÃ¢â‚¬â„¢s lead character to exhibit certain flaws and weaknesses, notably indecisiveness?
IÃ¢â‚¬â„¢m not saying that weaknesses or flaws in the design characteristics of organisms or ecosystems can be the basis for a design inference. Design inferences are drawn by identifying features of systems that are uniquely diagnostic of intelligence. At the same time, weaknesses or flaws in the design characteristics of organisms or ecosystems could be compatible with evolutionary changes guided by an intelligence. Nor would such an evolutionary scenario, in which not every aspect of organisms taken in isolation is optimal, entail that any intelligence guiding evolutionary change would have to be flawed.