What Good Is Half A Wing?

I've read arguments against evolution saying that it is hard to imagine an incremental development of species over time. Arguments as such often culminate into "what good is half a wing" kind of statements. The criticism is intuitive: it is hard to imagine, if wings developed over time from skin to a flap of hide to a full-blown wing, little by little, what good half a wing or one-eighth of a wing would be.

The basic counterargument sounds somewhat silly only because it is an answer addressed to an almost inane question. One can imagine that perhaps half a wing enabled its user to jump higher or float when descending down tall heights, aiding it some way or other in survival. However, what is more important that needs to be addressed is the nature of the assumption that half a wing is useless, because what makes one so sure right now that the standard wing model we see is a full wing? Thousands of years later the wing might develop into something else that enables much more advanced aerial navigation perhaps, and maybe then 'intelligent' but pompous life forms might be wondering what on earth these creatures could have done with 'half a wing', which is what we have today.

Additionally, to think that something is inconceivable simply because one 'can't imagine it' is simply bad science. Biological and physiological organs and functions do not exist for aesthetic reasons, and if anything it is the job of the scientist to 'imagine' what good that adapted object has/had that made it suited to survival at one time or other. Scientific progress hinges on this.