7.2 Irreducible Complexity
The term “irreducible complexity” was introduced by biochemist Michael Behe in his 1996 book “Darwin’s Black Box”. Behe defines it as “a single system which is composed of several well-matched interacting parts that contribute to the basic function, wherein the removal of any one of the parts causes the system to effectively cease functioning”.
Critics point out that the irreducible complexity argument assumes that the necessary parts of a system have always been necessary and, therefore, could not have been added sequentially. They argue that something which is at first merely advantageous can later become necessary as other components change. Furthermore, they argue, evolution often proceeds by altering preexisting parts, or by removing them from a system, rather than by adding them. This is sometimes called the “scaffolding objection”.