In order to say that some function is understood, every relevant step in the process must be elucidated.

Since natural selection requires a function to select, an irreducibly complex biological system, if there is such a thing, would have to arise as an integrated unit for natural selection to have anything to act on.

The trap does not work until all the parts were there. The system itself doesn't work until you fit all of them together.

In order to say that some function is understood, every relevant step in the process must be elucidated.

As commonly understood, creationism involves belief in an earth formed only about ten thousand years ago, an interpretation of the Bible that is still very popular. For the record, I have no reason to doubt that the universe is the billions of years old that physicists say it is. Further, I find the idea of common descent (that all organisms share a common ancestor) fairly convincing, and have no particular reason to doubt it.

It is often said that science must avoid any conclusions which smack of the supernatural.

In many biological structures proteins are simply components of larger molecular machines.