In his book Darwin’s Black Box, biochemistry professor Michael J. Behe, an evolutionist, acknowledges a “powerful challenge to Darwinian evolution”—something he calls “irreducible complexity.” This refers to a system with interacting parts, which is so complex it could not have come together piece by piece and still function. He gives a simple example: the humble mousetrap. The mousetrap has five major components that make it functional. If any one of these components is missing, it will not function. It is worthless as a mousetrap until all the components are in place.
He explains that an irreducibly complex system cannot be produced by slight, successive modifications, “because any precursor to an irreducibly complex system that is missing a part is by definition nonfunctional … Since natural selection can only choose systems that are already working, then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.”
One example in the human body is the knee joint, which contains at least 16 essential components. Since it is irreducibly complex, the knee could not have evolved gradually but must have been created all at once as a whole, fully functioning joint.
Charles Darwin admitted, “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down” (The Origin of Species).
Job 4:4 Your words have upheld him who was stumbling, And you thave strengthened the feeble knees;