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

In the abstract, it might be tempting to imagine that irreducible complexity simply requires multiple simultaneous mutations - that evolution might be far chancier than we thought, but still possible. Such an appeal to brute luck can never be refuted... Luck is metaphysical speculation; scientific explanations invoke causes.

Proteins are the machinery of living tissue that builds the structures and carries out the chemical reactions necessary for life.

The theory of undirected evolution is already dead, but the work of science continues.

We can look high or we can look low in books or in journals, but the result is the same. The scientific literature has no answers to the question of the origin of the immune system.

For example, both humans and chimps have a broken copy of a gene that in other mammals helps make vitamin C. ... It's hard to imagine how there could be stronger evidence for common ancestry of chimps and humans. ... Despite some remaining puzzles, there's no reason to doubt that Darwin had this point right, that all creatures on earth are biological relatives.

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.