That is a pretty big assumption to make. If you are saying that our understanding is limited at this point in time, then I'd agree. Barring loss of data/memory, our understanding will always be limited now compared to our understanding in the future.
But if you are claiming there is some fundamental upper bound to our understanding, and that a complete functional understanding of the human body is beyond that upper bound, then I have to ask what motivates that claim.
Not to put too fine a point on it, but that kind of thinking is what supports flawed pseudoscience like "intelligent design" (not claiming you support that, and really not trying to open that can of worms; just drawing a parallel). Sure, if you assume that our understanding is already at some kind of limit, and then show something we can't explain, it follows naturally that it must have supernatural origins. If, on the other hand, you realize that our inability to explain something is most likely just a function of time (eventually we'll learn enough that we will be able to explain it), then the argument seems absurd.