This is one of the more common arguments that get thrown at me by creationists. The argument for "irreducible complexity" which claims that some complex organs and systems present in humans and animals can function only in their current state and would have no benefit to the organism in a less advanced (evolved) state. Therefore, the assertion that the organ or system evolved from a simpler form does not hold up rationally. The human eye being perhaps the most cited example.
This is, as I'm sure you could have guessed, a bogus claim. One made in a retroactive fashion, by which I mean the "evidence" was actively sought to support a prior belief or claim. This is in contrast to the scientific approach, which is to gather evidence and draw conclusions from those observations, regardless of whether or not they are pleasant, popular, or contradictory to what has been traditionally believed.
This video does a rather nice job of summarizing the reality of the situation, and how the eye did evolve from less complex structures.