Mission for Truth
I remember Richard Dawkins addressed this arguement in his book Climbing Mount Improbable.It dealt with the insistence of locating the "missing link" in the ape-human transition.Since we must categorize apes to one side and humans to another even though we do find close approximations to one another in terms of features we must eventually place it within a category.Over time the distinction becomes finer however there will always be distinctions and therefore must eventually fall into either ape or human.It is a failure of our classification system that there is no actual "in between" classification.
Creationists say that the transitionary fossils are either ape or human but fail to think that this is precisely what we would expect from a fossil record that evolved.Now I wonder if they have an explanation of their own?